Unitfxi States

Department of

Agriculture

The Nantucket Pine Tip IMoth:

Old Problems, New Research

Forest Service

Proceedings of an Informal Conference

The Entomological Society of America,

Southern

Annual Meeting

Research Station

General Technical Atlanta, Georgia

Report SRS-51 December 12-I 6, 1999
Cover: Nantucket pine tip moth adult.

Photo by Julie C. Weatherby.

DISCLAIMER

The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S.

Department of Agriculture of any product or service.

PESTICIDE PRECAUTIONARY STATEMENT

This publication reports research involving pesticides. It does not contain recommendations for their use, nor does it

imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate

State and/or Federal agencies before they can be recommended.

CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, and fish or other wildlife if they

are not handled or applied properly. Use all herbicides selectively and carefully. Follow recommended practices for the

disposal of surplus pesticides and their containers.

Papers published in these proceedings were submitted by authors in electronic media. Editing was done to ensure a

consistent format. Authors are responsible for content and accuracy of their individual papers.

June 2002

Southern Research Station

P.O. Box 2680

Asheville, NC 28802
The Nantucket Pine Tip Moth:

Old Problems, New Research

Proceedings of an Informal Conference

The Entomological Society of America, Annual Meeting

December 12-I 6, 1999

Atlanta, Georgia

Edited by

C. Wayne Berisford, Professor

Department of Entomology

University of Georgia

Athens, GA 30602-2603, USA

Donald M. Grosman, Entomologist II

Texas Forest Service

Cudlipp Forestry Center

P.O. Box 310

21127 South First Street

Lufkin, TX 75902-0310, USA

Sponsored by

The University of Georgia

USDA Forest Service, Southern Research Station

Table of Contents

Page

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

Page

Tip Moth Parasitoids and Pesticides:

Are They Compatible? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Kenneth W McCravy, Mark J. Dalusky: and

C. Wayne Berisford

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Impact of Pine Tip Moth Attack on Loblolly Pine . . . . . . . . . .

Roy Hedden

1

Interaction of Forest Management Practices

and Tip Moth Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

John T: Nowak

8

Evaluation of Candidate Insecticides for Control of

the Nantucket Pine Tip Moth (Lepidoptera:Tortricidae) 14

Mark J. Dalusky and C. Wayne Berisford

Maximizing Pine Tip Moth Control: Timing is

Everything . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Christopher J. Fettig

The Potential for Trichogramma Releases to

Suppress Tip Moth Populations in Pine Plantations . . . . 34

David B. On, Charles P-C. Sub, Michael Philip,

Kenneth W McCravy, and Gary L. DeBarr

Use of Pheromone Traps to Predict Infestation

Levels of The Nantucket Pine Tip Moth:

Can It Be Done? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Christopher Asaro and C. Wayne Be&ford

Nantucket Pine Tip Moth, Rhyacionia Frustrana,

Lures and Traps: What is the Optimum Combination . . . 56

Gary L. DeBarr; J. Wayne Brewer,

R. Scott Cameron and C. Wayne Berisford

. . .

III
PREFACE

The Nantucket pine tip moth is an enigmatic insect whose

perceived importance as a pest has waxed and waned

through the years. Although it rarely kills trees, attacks by

the moth kill growing shoots and can cause growth loss

and poor form. The moth has been the subject of a

considerable amount of research at times and has almost

been ignored during other periods. For example, there was

a spate of research during the late 1950’s and 1960’s

when large acreages were converted from agriculture to

pine plantations. After that period, there appeared to be little

interest in the moth during the 1970’s and 80’s. However,

another round of conversions from agriculture to pine

plantations occurred via the Federal Conservation Reserve

Program in the 1980’s and 90’s. Also, the concomitant

development of intensive plantation management which

included intensive mechanical site preparation, herbicide

applications to control competing vegetation and

fertilization, apparently exacerbated tip moth infestations

and created renewed interest in research.

The most recent peak of interest led to the formation of the

Pine Tip Moth Research Consortium which combined

resources from several public and private institutions to

provide funding and bring expertise to bear on the

problems caused by tip moth infestations in intensivelymanaged stands. The initial idea for the Consortium was

developed by F. S. Broerman, Union Camp Corporation and

Steven A. Cade, Weyerhaeuser Company. The Pine Tip

Moth Research Consortium had six industrial members

when it was initiated in 199596 including: Champion

International Corporation, Georgia Pacific Corporation,

International Paper Corporation, Jefferson Smurfit

Corporation, Union Camp Corporation and Weyerhaeuser

Company. The USDA Forest Service was also a member

via the Forestry Sciences Lab, Research Work Unit No.

4505 based in Athens, Georgia. The Consortium was

administered through the University of Georgia with

participation by the Department of Entomology and the

Warnell School of Forest Resources. The program was

directed by C. W. Berisford, Department of Entomology. In

addition to voting members, there were several associate

industrial members of the Consortium who made financial

contributions and provided materials for direct tip moth

control evaluations. Associate members included Abbott

Laboratories, American Cyanamid Company, Bayer

Corporation, Dow AgroSciences LLC, Gowan Company,

Rohm & Haas Company, Valent U. S. A. Corporation and

Zeneca Ag Products.

Additional resources were provided by the Georgia

Traditional Industries Program in Pulp and Paper (TIP3) via

competitive grants and the USDA Forest Service as

cooperative agreements through the Forest Health

Technology Enterprise Team, Morgantown, West Virginia

and a Special Technology Development Project sponsored

by Forest Health Management, Region 8, Atlanta, Georgia.

Other institutions which provided resources and/or

expertise were: Clemson University (Dr. Roy L. Hedden),

The Texas Forest Service, Pest Control Section (Dr. Donald

Grosman), Auburn University (Dr. J. Wayne Brewer).

Through the efforts of the Consortium members and their

cooperators, a body of new information regarding the

biology and control of the tip moth was developed. In

conjunction with the Entomological Society of America

annual meeting, an Informal Conference was held on

December 13, 1999 to review some new research and to

provide a forum for discussions of future research.

We sincerely appreciate the help and advice of Mr. Jimmy

Seckinger, International Paper Corporation on various field

projects. We are grateful to Dr. Kerry Britton, USDA Forest

Service, Southern Research Station for sponsoring

publication of these proceedings.
EXECUTIVE SUMMARY

The Nantucket pine tip moth has become a more prevalent

pest as the intensity of pine plantation management has

increased. Because some forest product producers feel

that growth losses due to tip moth attacks may be

unacceptable, the Pine Tip Moth Research Consortium

was formed to increase basic knowledge about the moth

and to explore ways to reduce tip moth damage. A

conference was held in 1999 to highlight some research

supported by the consortium and other institutions.

Research has been conducted on damage assessment

(impact), interactions of the moth with different forest

management practices, effects of herbicide and insecticide

use on tip moth parasitoids, evaluations of insecticides for

tip moth control, optimizing chemical control through more

precise timing, potential for augmenting tip moth egg

parasites, pheromone traps to predict tip moth infestation

density and tests of different pheromone trap designs and

lures.

Models were developed to relate tree growth to tip moth

infestation levels. Tip moth attacks were found to have their

greatest effect on tree height growth during the early

generations in each growing season in the first three years

following stand establishment.

Tip moth infestation levels increased as management

intensity increased, particularly in regard to control of

competing vegetation. Tip moth populations appeared to

be less stable in plots with the highest management

intensity, ranging from epidemic levels to almost no

infestation over IO consecutive generations..

Tests of various insecticides showed that a wide variety of

insecticide types and formulations could provide effective

tip moth control. Some insect growth regulators showed

considerable promise for tip moth control with minimal

impact on natural enemies. It appears that there will be a

variety of insecticides available for tip moth control in the

future since most of the compounds tested are also

labeled for use on major agricultural crops.

Effective tip moth control with insecticides is highly

dependent on proper timing. Several timing techniques

have been developed over the years and are briefly

reviewed. A new method is described which uses historical

temperature data from a grid of weather stations to predict

optimum times for chemical control of each tip moth

generation in areas with three or four generations

annually.

Studies of interactions among tip moth parasitoids,

herbicides and insecticides showed that overall parasitism

was not affected by herbicidal control of competing

vegetation although the relative contribution of some

parasitoids was changed. Parasitism was reduced by

certain broad spectrum insecticides but not all of the

parasitoids were affected equally with some species

apparently unaffected while others were virtually eliminated.

It appears that pesticides for tip moth control and

parasitoids can be compatible if insecticides are selected

to minimize impact on these natural enemies.

Experimental releases of the native tip moth egg parasite

Trichogramma exiguum showed that there may be some

potential for augmentative releases of lab-reared parasites.

Impact evaluations showed that the egg parasites reduced

larval populations by 60 percent. Although the percentage

of tip moth-infested shoots was not different from those in

untreated check plots, the amount of damage to infested

shoots was significantly reduced due to fewer larvae per

shoot. Trichogramma survival was higher in areas in which

some vegetation had been retained between rows of

planted pines.

Traps baited with synthetic pheromone lures have been

used to monitor tip moth activity and to help with timing of

control attempts. In the past, it was assumed that trap

catches of male tip moths did not relate to populations and

therefore could not be used to estimate population density.

However, by standardizing traps and baits, plus correcting

for differential male longevity during different generations, it

may be possible to make reasonably accurate population

estimates. Additionally, a method has been developed to

predict damage based on catches of moths from the

previous generation.

Although pheromone-baited traps have been used to

monitor tip moth activity, time insecticide applications and

may be used in the future to quantify populations or predict

damage, there is no “standard” trap or pheromone bait.

Workers have been using a variety of systems which do not

allow comparisons of information gathered by trapping.

There are a number of commercially available baits and

traps, but they have not been compared. Several traps and

lures were tested to determine which were the most

effective and consistent for catching tip moths. Pherocon

lCR wing traps consistently caught more moths, but most

designs caught moths at the same time at the beginning of

moth emergence. Several available lures worked well but

were effective for different lengths of time.

V

INTRODUCTION

The Nantucket pine tip moth, Rhyacionia frusfrana

(Cornstock) (Lepidoptera: Tortricidae), is one of the most

common forest insects in the Southeastern United States

(Berisford 1988). Although it is usually considered to be a

southern pest, the range of the moth includes much of the

eastern half of the United States, southern Mexico and

Central America (Powell and Miller 1978). It is also

established in southern California and parts of Arizona and

New Mexico where it was accidentally introduced.

Most hard pines are susceptible to attack by R. frusfrana,

but there are considerable differences in relative

susceptibility. For example, among the southern pines,

shortleaf (Pinus echinafa mill.), loblolly (P faeda L.), and

Virginia pines (f? virginiana Mill.) are highly susceptible,

while slash pine (P elliottii Engelm.) is highly resistant and

longleaf pine (P palusfris Mill.) is virtually immune to attack

with the exception of very young nursery seedlings.

Monterey pine (f? radiafa D. Don), is highly susceptible in

the introduced range in southern California (Striven and

Luck 1978) and ponderosa pine (P ponderosae Douglas

ex. Laws.) is frequently attacked in Arizona and New

Mexico.

The natural range of R. frusfrana in the United States

overlaps with at least three other common species of

Rhyacionia. Its most common associate, the pitch pine tip

moth, R. rigidana (Fernald), often shares the same hosts

(Baer and Berisford 1975, Miller and Wilson 1964) and at

least some of their life stages overlap (Berisford 1974,

Canalos and Berisford 1981). The range of R. frusfrana

overlaps to a lesser degree with that of the subtropical pine

tip moth, R. subtropica Miller, and an introduced species,

the European pine shoot moth, R. buoliana (Schiffermuller)

(Powell and Miller 1978).

Damage caused by R. frusfrana may be serious, resulting

in severe stunting and stem deformation, and, in extreme

cases, death of the host (Yates and others 1981). However,

damage is often transitory or negligible in many forest

stands. The reasons for radically different tip moth

populations and/or damage in different stands are not fully

understood, but they appear to be at least partly related to

tree species, site quality, natural enemies, and competing

vegetation. The latter is often a function of the intensity of

site preparation prior to planting and/or the use of

herbicides to control competing vegetation.

Tip moth damage is most severe on seedlings and

saplings, usually under 5 years old, and is usually

manifested as growth loss and/or loss of tree form. The

excessive branching and competition among lateral limbs

for dominance following heavy attacks can result in

significant increases in compression wood and loss of

wood quality (Hedden and Clason 1980). Form loss is

particularly important on ornamentals and Christmas

trees, which may become virtually worthless if tip moth

attacks are not controlled. The long term impact of R.

frusfrana attacks, particularly on tree height growth, is

controversial. Some studies show permanent losses, some

indicate temporary losses that are regained, and others

show no effect. Cade and Hedden (1987) showed long-term

growth losses in Arkansas and reviewed the literature

pertaining to tip moth impact.

Within the natural range of R. frusfrana, the life cycle is

synchronized with its primary hosts to produce a new

generation of egg-laying adults when a new growth flush

begins. This synchrony provides larvae with soft, nutritious

meristematic tissue in which to feed during their early

development. The moth has two to five generations

annually, depending on the climate. Generations are

usually discernible, but considerable overlap may occur

after mid-summer, even in areas with as few as three

annual generations (Gargiullo and others 1984, Fettig and

Berisford 1999). The moth over-winters as pupae within

shoots that have been killed by larval feeding. Development

occurs above a threshold of 9.5X (Haugen and Stephen

1983) and adults may emerge in late December or January

in the southern part of its range. Adults are normally

crepuscular, but late afternoon flights may occur preceding

evening temperatures that fall below the flight temperature

threshold of 10°C. This early flight behavior is apparently

triggered by daytime temperatures just above the threshold

(Webb and Berisford 1978). Males begin to emerge before

females and large numbers are often present when the first

females appear (Berisford and Brady 1972). Mating is

mediated by a sex pheromone (Berisford and Brady 1972).

Two pheromone components have been identified as (E)-9-

dodecenyl acetate and (E)-9, 1 I-dodecadienyl acetate (in a

ratio of 96: 4) (Hill and others 1981). Rbyacionia frusfrana

responds weakly to the pheromones of R. subtropica and R.

buoliana, but neither of these species are attracted to R.

frusfrana (Berisford and others 1979).

Mating occurs shortly after emergence, and eggs are

deposited on shoots and needles. Females oviposit

almost exclusively on highly susceptible hosts such as

loblolly pine even when they are adjacent to resistant hosts

such as slash pine (Hood and others 1985). The first visible

evidence of tip moth attack is often small drops of resin

exuding from needle bases, where first instar larvae have

begun to feed. Second instars feed at needle or bud axils

where they construct a characteristic silk tent which

becomes covered with resin. Subsequent instars feed

inside buds and shoots, and fully grown larvae pupate

inside the dead shoots (Yates and others 1981). Multiple

infestations are common with up to 15 individuals per

shoot, depending on population density and shoot

diameter.

Rhyacionia frusfrana has a substantial complement of

parasitoids and predators (Eikenbary and Fox 1965). Most

data on natural enemies have come from mass rearings

from tip moth-infested shoots, but a few studies have

attempted to more precisely determine the roles of the

associated arthropods. Fourteen species of insects and

seven spiders have been observed to prey on the tip moth

vii
in the field and laboratory (Eikenbary and Fox 1968a). No

estimates of impact were made in studies by Eikenbary

and Fox, but spiders were the most abundant predators

during the summer, and two species of clerid beetles

(Phyllobaenus spp.) were apparently most important during

the spring (first) generation. Although there are a number of

parasitoids associated with R. frusfrana, including 26

Hymenoptera and one Diptera species (Warren 1985) only

a few appear to be sufficiently abundant to have significant

impact on tip moth populations. Parasitoids from individual

R. frusfrana larvae and pupae have been reared to help

determine their specific parasitic roles, particularly those

species reported to be cleptoparasites and hyperparasites

(Freeman and Berisford 1979). One of the more abundant

species found in rearings ((Eurytoma pini Bugbee

(Hmenoptera: Eurytomidae)) is primarily cleptoparasitic (i.e.,

attacking only previously parasitized larvae), although it

may also be a primary parasitoid or hyperparasitic.

However, conditions under which it is a primary or a

secondary parasitoid are unknown. Most studies on larval

and pupal parasites have shown that the ichneumonid

wasp, Campoplex frustranae Cushman, and the tachinid fly,

Lixophaga mediocris Aldrich, were the most abundant. They

constituted 23 and 45 percent of all parasitoids,

respectively, when averaged over four generations in

Georgia (Freeman and Berisford 1979). However, C.

frustranae was absent from samples of 8 consecutive

generations in the Georgia coastal plain (McCravy and

Berisford 2000). The next most abundant parasitoids were

Eurytoma pini (11 percent) and Perilampus fulvicornis

Ashmead (Eupelmidae) (6 percent) . The role of P.

fulvicornis is unclear, as it appears to function both as a

primary parasite and as a hyperparasite.

Egg parasites (Trichogramma spp.) appear to be important

in regulating tip moth populations, with up to 64.5 percent of

the eggs being parasitized (Yates 1966). Egg parasitism

was heavier in summer than in the spring generation, in two

studies in the Georgia Piedmont Plateau (Gargiullo and

Berisford 1983, McCravy and Berisford 1998). Lower egg

parasitism in the first generation could be due to poor

survival of overwintering Trichogramma wasps or to the

presence of many alternate hosts in the spring. Overall egg

mortality was also found to be density-dependent, and most

of this morality was due to Tricbogramma parasitism

(Gargiullo and Berisford 1983). By contrast, no evidence of

density-dependent responses has been observed among

larval and pupal parasitoids (Eikenbary and Fox 1968b).

Life table studies showed that most tip moth mortality

occurred during the egg, late larval, and pupal stages

(Gargiullo and Berisford 1983). Egg mortality was mostly

due to Trichogramma spp., while considerable pupal

mortality was caused by C. frustranae. Campoplex

frusfranae was released into introduced R. frustrana

infestations in California where it significantly reduced tip

moth damage (Striven and Luck 1978).

The abundance of R. frustrana is strongly affected by the

availability of preferred hosts which are in susceptible age

classes (usually 1-5 years). Plantations are capable of

producing large populations within one year of

establishment. Colonization of pine plantations is often

rapid, with initial infestations being random but becoming

clumped in later generations (Clarke 1982). Peak

infestations usually occur 2-4 years after establishment

when population levels are positively correlated with the

number of available shoots (Lashomb and others 1980).

Although the number of available shoots increases with

time and tree height, the proportion of shoots infested

declines, suggesting that other factors such as host

resistance, asynchrony of growth flushes and moth

emergence or parasitism, may reduce the success of the

moth as trees become older.

The highest tip moth numbers and damage tend to occur in

even-aged stands with little competing vegetation and/or

low vegetation diversity. For example, plantations in old

fields generally have higher infestations than do natural

stands with the same average spacing (Berisford and

Kulman 1967). Several studies have shown increased tip

moth infestations concomitant with decreases in amount

and/or diversity of competing vegetation (Hertel and

Benjamin 1977, Hood and others 1988, Miller and Stephen

1983, Ross and others 1990b, Warren 1963, White and

others 1984). Intensive stand management techniques

which normally include mechanical site preparation,

herbicides and fertilizer, increase tree growth but may also

increase tip moth damage. These practices may, among

other things, decrease the availability of alternate hosts and

other food sources such as pollen and nectar, for natural

enemies.

Site quality may also affect tip moth populations and/or

damage. Poor sites had higher tip moth populations in the

Piedmont Plateau region in the Southern U.S., with site

index being negatively correlated with tip moth infestations

(Hood and others 1988). However, high tip moth

populations were found to be associated with higher site

indices in Texas (White and others 1984). Specific soil

characteristics, such as texture, depth of “A” horizon,

calcium content, pH, and percentage and/or depth of clay,

were correlated with infestation levels, but site index and

soil calcium accounted for much of the variation in the

Piedmont Plateau. Although there are no definitive data on

the effects of site quality on resistance to tip moth attack, it

seems likely that root establishment is faster on better sites,

thereby increasing the general health of the seedlings.

Some resistance is apparently due to high resin flow (Yates

1962) or perhaps to induced hypersensitive reactions, such

as that often associated with bark beetles (Raffa and

Berryman 1983). High nutrient levels which produce healthy

trees may also provide some measure of protection via

tolerance to tip moth attacks. Ross and Berisford (1990)

found that loblolly pine seedlings which had received high

levels of nutrients and water supported higher tip moth

populations, but suffered proportionately less damage than

trees receiving low nutrients and water even though those

trees had lower infestations. Rapid growth provided by

good sites also reduces the period during which trees are

highly susceptible, since infestation generally decreases

with tree height and age.

Methods for detection of R. frustrana are diverse but there is

no “standard” methodology. Pheromone traps are often

employed to determine when tip moth emergences occur,

VIII
but no trap catch-damage thresholds have been

established. Pheromone traps are usefully employed for

timing of insecticide applications for tip moth control

(Gargiullo and others1985). It appears that most detection

methods rely on simply looking for evidence of damage,

usually dead shoots, and confirming that a tip moth

infestation exists. Most observers apparently assume that

infestations are R. frusfrana, although there may be other

species present as previously mentioned.

Methods for damage evaluation are mostly based on

numbers of infested shoots per tree or percentage of

available shoots infested. However, there are currently no

guidelines by which damage (growth loss) may be

predicted by counts of infested shoots. Reliable sampling

methods have been developed for determination of tip

moth populations on a shoot, tree, or area (hectare) basis

(Gargiullo and Berisford 1981, Gargiullo and others 1983).

However, the necessary links between population

estimates and damage predictions have not yet been

established. Although it may seem surprising that damage

prediction methods or damage thresholds for R. frustrana

have not been developed, it might be expected in light of the

previous contradictory information regarding transitory vs

permanent damage.

Rhyacionia frustrana infestations in pine plantations have

generally been regarded as inevitable and uncontrollable.

Since tip moths rarely kill trees, and their impact on volume

and form is highly variable, management has generally

been focused on maintaining stand vigor through

appropriate silvicultural treatments in both natural and

plantation forests. As the acreage of intensively managed

pine plantations has increased to maximize fiber and

timber production on a shrinking land base, R. frustrana

has emerged as a more serious and persistent pest

problem.

A system for managing Rhyacionia frustrana in pine

plantations would likely include the following components:

1) a hazard-rating system to make pre-established

predictions of potential damage, 2) practical survey

techniques to determine current population levels, 3)

economic thresholds, or action thresholds, to trigger the

use of direct control activities, 4) safe and effective

insecticides 5) models to assist with proper timing of

insecticide treatments, 6) genetically resistant planting

stock, 7) cultural practices that reduce tip moth populations

and/or their damaging effects on pines, and 8) techniques

for augmenting the effectiveness of natural control agents.

Only a few of these components have been thoroughly

investigated or are currently used in forest plantation

management.

A substantial body of information has been accumulated on

R. frustrana biology and control through many years of

study. However, this research has been fragmented and

generally uncoordinated and considerable additional work

will be required to eventually develop integrated pest

management programs. With the widespread adoption of

intensive forest management, highly visible tip moth

damage has increased interest in research on Rhyacionia

species, especially R. frusfrana. More comprehensive work

with well-defined objectives, structure, and linkages with

forest management systems is essential. The Pine Tip Moth

Research Consortium was formed in 1995 to conduct

research on tip moth problems associated with intensively

managed loblolly pine plantations. The Consortium, based

at the University of Georgia, Department of Entomology,

consisted of six forest companies, The U. S. Forest Service

and The University of Georgia. The primary areas targeted

for investigation by the Research Consortium included:

impact, improved insecticidal control, natural enemies,

effects of cultural treatments, population and damage

estimates and evaluations of pheromone lures and traps.

REFERENCES

Baer, R. G.; Berisford, C. W. 1975. Species composition of pine tip

moth Rhyacionia spp. infestations in northeast Georgia. Journal

of the Georgia Entomological Society. 10: 64-67.

Berisford, C. W. 1974. Comparisons of emergence periods and

generations of pine tip moths, Rhyacionia frusfrana and R.

rigidana. Annals of The Entomological Society of America. 67:

666-668.

Berisford, C. W. 1988. The Nantucket pine tip moth. ln: Berryman,

A. A. ed. Dynamics of forest insect populations: patterns,

causes, and inplications. New York: Plenum Publishing

Corporation: 141-161.

Berisford, C. W.; Brady, U. E. 1972. Attraction of Nantucket pine tip

moth males to the female sex pheromone. Journal of Economic

Entomology. 65: 430-435.

Berisford, C. W.; Harman, D. M.; Freeman, B. L.; Wilkinson, R. C.;

McGraw, J.R. 1979. Sex pheromone cross-attraction among

four species of pine tip moths, Rhyacionia species. Journal of

Chemical Ecology. 5:205-210.

Berisford, C. W.; Kulman, H. M. 1967. Infestation rate and damage

by the Nantucket pine tip moth in six loblolly pine stand categories. Forest Science 13: 428-438.

Cade, S. C.; Hedden, R. L. 1987. Growth impact of pine tip moth on

loblolly pine plantations in the Ouachita mountains of Arkansas.

Southern journal of Applied Forestry. 11: 128-133.

Canalos, C. G.; Berisford, C. W. 1981. Seasonal activity of two

sympatric Rhyacionia species determined by pheromone traps.

Journal of The Georgia Entomological Society. 16: 219-222.

Clarke, S. R. 1982. Dispersion of the Nantucket pine tip moth,

Rhyacionia frustrana (Comstock), in newly established loblolly

pine plantation. M. S. thesis, University of Arkansas,

Fayetteville, Arkansas.

Eikenbary, R. D.; Fox, R. C. 1965. The parasites of the Nantucket

pine tip moth in South Carolina. South Carolina Agricultural

Experiment Station, Technical Bulletin 1017. 9 p.

Eikenbary, R. D.; Fox, R. C. 1968a. Arthropod predators of the

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IMPACT OF PINE TIP MOTH ATTACK ON LOBLOLLY PINE

Roy Hedden’

Abstract-Data on the impact of Nantucket pine tip moth, Rhyacionia frustrana, attack on the height of loblolly pine, Pinus

faeda, in the first three growing seasons after planting from three locations in eastern North Carolina (U.S.A.) was used to

develop multiple linear regression models relating tree height to tip moth infestation level in each growing season. These

models were used to demonstrate which tip moth generations cause significant damage to the tree, thus facilitating the

identification of generations that are good candidates for tip moth control. The height impact models were also used to

calibrate a pine growth model to estimate volume loss associated with tip moth attack. Lastly, an example of how to use the

information on volume impact to economically evaluate a potential pine tip moth control program is presented.

INTRODUCTION

Over 12 studies documenting some aspect of pine tip moth

impact have recently been reviewed and summarized

(Hedden 1998). However, none of these studies contain

detailed information on the relationship between tip moth

infestation level and tree growth. Most of the studies consist

of one or more locations where there were a group of plots,

half of which received some form of tip moth control while

the other half received no treatments. Also, many of them

described tip moth infestation in qualitative terms, or only

measured tip moth level once during the year, usually for the

overwintering generation. Consequently, these studies are

not useful for developing models relating tip moth infestation

levels to growth impact of the tree. However, such models

are needed to predict long term impact of tip moth attack on

pine growth, and to evaluate the economic feasibility of

developing a pine tip moth control program.

The purpose of this paper is to present models relating

Nantucket pine tip moth infestation levels to loblolly pine

growth. In addition, we will show how these models can be

used to estimate long-term impact of tip moth attack on pine

yield, and how this information can be used to make

decisions about a pine tip moth control program.

METHODS

Field plots were installed in three locations in eastern North

Carolina in 1985 and 1986 to evaluate loblolly pine for tip

moth resistance (Cade and Hedden 1989). All locations had

moderate to high organic soils; planting sites were drained,

intensively site-prepared by piling and burning the residual

slash, and bedded. An aerial application of sulfometuron

methyl for herbaceous weed control was applied to all sites

in May of the year of planting. One location (LOC2) was

installed in 1985, and two (LOCI and LOC3) in 1986. Oneyear-old nursery seedlings from half-sib families were

planted in replicated plots in March. Families included in the

study were from genetically improved parents, and were well

represented in operational plantings in the area. Five pine

families were common to all three sites. The experimental

design was randomized block with split plots. At each

location, either 36-tree plots with three blocks (1985) or 24-

tree plots with four blocks (1986) were installed. All trees in a

given plot were of the same family, i.e., one plot per family.

The plots were split with one-third of the trees on each plot

receiving insecticide treatments to protect them from pine tip

moth attack. The study site established in 1985 received the

insecticide treatment in the second (1986) year only; at the

other two locations, insecticide treatments were applied in

both 1986 and 1987. The first-year insecticide treatment

consisted of 0.5 g active ingredient (Al) of carbofuran

granules applied to each seedling at the time of planting.

Second-year insecticide applications consisted of one of the

following: (1) carbofuran granule application at a rate of 5 g

Al per cm of basal diameter per tree incorporated into the

soil at the base of the tree, or (2) foliar applications of

fenvalerate timed to coincide with each tip moth generation.

Tree heights were measured at the beginning of each

growing season and at the end of each tip moth generationlate June, early August, and October. Basal diameter was

measured at the beginning of the growing season and at the

end of the growing season in 1987. The number of growth

flushes during the growing season was also recorded for

each tree. Tip moth infestation level was recorded at each

measurement period in the first growing season by recording

the infestation status of the terminal bud only. Thereafter, the

number of infested and uninfested buds in the terminal whorl

of branches immediately below the terminal bud was also

recorded. Data were collected for the first and second years

for the two sites established in 1986. Data were collected in

the second and third year for the site installed in 1985.

The data from the sites was grouped by growing season [two

first-year sites (LOC2 and LOC3), three second-year sites

(LOCI, LOC2 and LOC3) and one third-year site (LOCI)].

The relationship between tip moth infestation level and tree

height was modeled using stepwise multiple linear

regression (SAS 1988). Data from individual trees were used

in all analyses for the five pine families common to all three

sites. Two sets of models were developed for each growing

’ Department of Forest Resources, Clemson University, Clemson, SC 296344003, rhddn@clemson.edu.

Citation forproceedings: Berisford, C. Wayne; Grosman, Donald M.. eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.
season-a full model containing information on site, family,

treatment, initial tree height and infestation level, and a

reduced model consisting of initial tree height and infestation

level were generated for each growing season.

Dummy categorical regressors were used to express several

variables. Insecticide treatment (TRT) was coded as 1 for

treatment and 0 for no treatment. Two variables (SITE1 and

SITE2) were used to code sites-SITE1 was 1 for LOCI and

0 for LOC2 and LOC3, and SITE2 was 1 for LOC2 and 0 for

LOCI and LOC3. Four categorical variables (FAMI, FAM2,

FAM3 and FAM4) were used, in a manner similar to the site

variables, to express the five pine families. All dummy

regressors for either the site or family variable were included

if at least one of the individual dummy variables was found

significant.

Yield information for loblolly pine was generated from the

whole stand equations of Burkhar-t and others (1972). Total

cubic feet inside bark and cords of pulpwood to a four-inch

top were for unthinned stands with a site index of 70 (base

age 25) at age 15. Tip moth impact was simulated by

reducing the average height of the dominant and

codominant trees in the stand. A stumpage value of $30 per

cord was used in calculating the present value of Nantucket

pine tip moth attack (Timber Mart-South 1997). English units

will be used when discussing pine yield because these are

the units in the timber trade in the U.S.

RESULTS AND DISCUSSION

Seasonal Tree Height Models

The full model for estimating loblolly pine height undergoing

Nantucket pine tip moth attack in a specified year is:

HT = b, + b, IHT + b, FLUSH + b, SITE1 + b, SITE2 + b,

FAMI + b, FAM2 + b, FAM3 + b, FAM4 + b, TRT + b,,

TII + b,, T12 + b,, T13 + b,, PBII + b,, PB12 + b,5 PB13

where

HT = tree height at the end of the growing season (cm)

FLUSH = number of growth cycles during the growing

season

IHT = tree height at the beginning of the season (cm)

SITE1 = dummy variable for location (0 or 1)

SITE2 = dummy variable for location (0 or 1)

FAMI = dummy variable for family (0 or 1)

FAM2 = dummy variable for family (0 or 1)

FAM3 = dummy variable for family (0 or 1)

FAM4 = dummy variable for family (0 or 1)

TRT = dummy variable for insecticide treatment (0 or 1)

TII = terminal infestation in generation 1 (0 or 1)

T12 = terminal infestation in generation 2 (0 or 1)

T13 = terminal infestation in generation 3 (0 or 1)

PBII = percent buds infested in the top whorl in

generation 1

PB12 = percent buds infested in the top whorl in

generation 2

PB13 = percent buds infested in the top whorl in

generation 3

The results of the stepwise regression for the first growing

season are shown in Table 1. Initial tree height at planting

and the number of growth flushes had a strong positive

effect on seasonal height growth. There were also significant

differences between location, family and treatment. Tip moth

infestation level had a significant negative effect on tree

Table I-Full and reduced regression models for predicting total tree height (cm) of loblolly pine during the first

growing season

Variablea

Full Modelb Reduced Model”

Regression Prob. Regression Prob.

i Coeff. (bi) Value Coeff. (bi) Value

CONSTANT 0 11.0248 0.0001 54.5492 0.0001

IHT 1 0.8736 0.0001 0.6598 0.0001

FLUSH 2 8.5571 0.0001

SITE1 3 4.2425 0.0001

FAMI 4 1.0063 0.3640

FAM2 5 0.4197 0.7181

FAM3 6 -3.1253 0.0055

FAM4 7 1.0411 0.3419

TRT 8 7.0248 0.0001

Tll 9 -10.3407 0.0001 -26.2401 0.0001

T12 1 0 -3.3799 0.0001 -8.3746 0.0001

T13 1 1 -5.3157 0.0001

R2 0.61 0.24

sy.x 10.5 14.6

N 936 936

“IHT is the initial tree height (cm); FLUSH is the number of annual growth flushes; SITE1 is location (0 or 1); FAMI, FAM2, FAM3 and

FAM4 is the pine family (0 or 1); TRT is the insecticide treatment (0 or 1); TII, Tl2 or T13 are the tip moth infestation of the terminal (0

or 1) in generation 1, 2 o r 3 .

bHT = b, + b, IHT + b, FLUSH + b, SITE1 + b, FAMI + b, FAM2 + b, FAM3 + b, FAM4 + b, TRT + b, TII + b,, T12 + b,, T13

“HT = b, + b, IHT + b, TII + b,, T12 + b,, 113

2
height in the first two tip moth generations. Loss of height

was greatest for attack in the first generation and least for

the second. Since infestation level was coded only as

terminal infestation in the first growing season, there was no

possibility for the percent infested buds in the top whorl to be

included in the regression model. Also, only SITE1 is

included in the full model since there were just two locations

for the first growing season. The model R* of 0.61 was quite

high for predicting height growth during the first year

considering that these seedlings were suffering from

transplant shock and they were in adapting to the site. It

should be noted that there was significant positive height

growth associated with the insecticide treatment that was

apparently not related to tip moth attack. There are many

insects that feed on young loblolly pine in addition to

Nantucket pine tip moth (Drooz 1985). Consequently, any

broad-spectrum insecticide application to control tip moth

will provide some growth enhancement from the control of

nontarget pests.

The reduced model for the first growing season only

includes initial tree height and tip moth infestation level

(table 1). In this case, tip moth attack in all three generations

had a significant negative impact on tree height. However,

the impact suffered in the second and third generations is

much lower than that occurring in generation one. This is

important since tip moth damage in the first generation is

easier to control than in the later generations. An insecticide

applied to the seedlings in the nursery would provide control

for the first tip moth generation. Cost of applying insecticides

to seedlings after planting is much more expensive.

Table 2 shows the results for the second growing season.

Initial tree height at planting and the number of growth

flushes had a strong positive effect on seasonal height

growth. There were also significant differences between

location, family and treatment. Tip moth infestation level had

a significant negative effect on tree height in all three tip

moth generations. Height reduction was greatest for the first

moth generation and least for the third. Both terminal and

first whorl infestation significantly affected tree height. The

R2 of 0.71 indicates a good fit of the model to the data.

The reduced model including only the variables for infested

terminals is also presented. This model explains about 58

percent of the variation in the data (R2=0.58). This model

also shows that tip moth infestation in the first two moth

generations has the greatest impact on tree height.

Table 3 shows the results for the third growing season. The

full model explained about 82 percent of the variation in the

data (R*=0.82). There were significant differences between

families. Initial tree height and the number of annual growth

flushes were positively related to tree height. Tip moth attack

Table 2-Full and reduced regression models for predicting total tree height (cm) of loblolly pine during the

second growing season

Variable”

Full Modelb Reduced Model”

Regression Prob. Regression Prob.

I Coeff. (b,) Value Coeff. (bi) Value

CONSTANT 0 65.9368 0.0001 100.2011 0.0001

IHT 1 1.4355 0.0001 1.5397 0.0001

FLUSH 2 9.6174 0.0001

SITE1 3 -14.1900 0.0001

SITE2 4 -15.3390 0.0001

FAMI 5 -7.5867 0.0001

FAM2 6 3.2094 0.0865

FAM3 7 -4.7245 0.0101

FAM4 8 -1.7952 0.3260

TRT 9 8.0130 0.0001

TII 1 0 -7.7853 0.0001 -15.9917 0.0001

T12 1 1 -4.8312 0.0002 -9.1509 0.0001

T13 1 2 -3.9598 0.0026 -5.5261 0.0002

PBII 1 3 -0.0674 0.0013

PB12 1 4 -0.0613 0.0017

PB13 1 5 -0.0420 0.0353

R* 0.71 0.58

sy.x 20.4 24.8

N 1254 1258

“IHT is the initial tree height (cm); FLUSH is the number of annual growth flushes; SITE1 and SITE2 are location (0 or 1); FAMI, FAM2,

FAM3 and FAM4 is the pine family (0 or 1); TRT is the insecticide treatment (0 or 1); TII, T12 or Tl3 are the tip moth infestation of the

terminal (0 or 1) in generation 1, 2 or 3; PBII, PBl2, and PB13 are tip moth infestation in the top whorl (%) in generation 1, 2, or 3.

bHT = b, + b, IHT + b, FLUSH + b, SITE1 + b, SITE2 + b, FAMI + b, FAM2 + b, FAM3 + b, FAM4 + b, TRT + b,, TII + b,, Tl2 + b,, T13

+ b,, PBII + b,, PB112 + b,,PBI3

“HT = b, + b, IHT + b,, TII + b,, T12 + b,, T13

3
Table 3-Full and reduced regression models for predicting total tree height (cm) of loblolly pine during the

third growing season

Variable”

Full Modelb Reduced Model”

Regression Prob. Regression Prob.

i Coeff. (bi) Value Coeff. (bi) Value

CONSTANT 0 68.7594 0.0001 93.1082 0.0001

IHT 1 11.1909 0.0001 1.2017 0.0001

FLUSH 2 7.1798 0.0001

FAMI 3 2.0258 0.5811

FAM2 4 -7.3505 0.0609

FAM3 5 -1.2501 0.7261

FAM4 6 -2.2580 0.5323

TII 7 -8.7146 0.0010 -11.3788 0.0001

PBII 8 -0.0478 0.1608

R2 0.82 0.80

sy.x 20.6 21.5

N 326 326

a IHT is the initial tree height (cm); FLUSH is the number of annual growth flushes; FAMI, FAM2, FAM3 and FAM4 is the pine family (0

or 1); TII is the tip moth infestation of the terminal (0 or 1) in generation 1; PBII is tip moth infestation in the top whorl (%) in

generation 1.

bHT=b~+b,IHT+b,FLUSH+b,FAM1+b,FAM2+b,FAM,+b,FAM4+b,Tll+b,PBll

CHT = b, + b, IHT + b, TII

of the tree in the first tip moth generation had a significant

negative impact on tree height. Attack during the second and

third generation had no negative effect on height. Trees

during this growing season are approaching the 3 meter

height threshold above which they normally escape

significant attack by the Nantucket pine tip moth. Once the

tree reaches three meters impact by this pest declines,

probably because moth attack no longer significantly

reduces potential leaf area of the plant, and because the

growth phenology of tree is changing from the juvenile to the

mature phase (Berisford 1988).

The reduced models for relating tree height to moth

infestation level in the first generation is shown in table 3.

This model explains about 80 percent of the variation in the

data (R*=0.80).

Linking Seasonal Tree Height Models

The individual seasonal height growth models can be linked

to investigate the effect of infestation level in a particular tip

moth generation on loblolly pine height. This procedure uses

the model for the first year to generate the initial height for

the second year, and then uses the model for the second

year to obtain the initial height for the third year.

Furthermore, if values for 0 percent infestation level are

substituted in each model then the tree height in the

absence of tip moth attack (UHT) is obtained. Conversely, if

values for 100 percent infestation level are substituted in

each model then the tree height in the presence of complete

tip moth attack is obtained. The difference between these

two values is the maximum potential height reduction due to

tip moth attack (DHT). The relative impact of tip moth attack

on tree height (RI) can then be expressed as (UHT - AHT)I

DHT where AHT is the estimated tree height under some

specified level of tip moth attack. Values of RI can vary from

0 (no attack) to 1 (complete attack).

An example will illustrate. The reduced model using only

terminal infestation will be used for all three growing

seasons. If tree height at planting (IHT) was 15.5 cm, the

maximum tree height (HT) without tip moth attack at the end

of the first growing season will be 64.8 cm. This value is then

used for the value of IHT in the second growing season, and

the end-of-season value obtained for HT (200.1 cm) is used

for IHT in the third season. Total height at the end of the third

season (333.3 cm) represents potential tree height in the

absence of tip moth attack (UHT). Total tree height at the

end of the third season under complete attack for all

generations would be 284.8 cm. Therefore, DHT = 333.3 -

284.8 = 48.5 cm, and RI = (333.3 - AHT)/48.5.

Now, using the same model and initial tree height at

planting, and setting the value of terminal infestation to one

and calculating tree height at the end the third year can

assess the potential impact of a tip moth generation in any

one of the three years. This value is then used to calculate

the RI for a given tip moth generation. Table 4 shows the

relative impact on tree height for each tip moth generation.

Results for the unweighted full and reduced models clearly

indicate that the greatest potential impact on tree height is

caused by attack during the first generation of each year.

Attack in the first generation just after planting is especially

harmful. This is not surprising since the tree is suffering from

transplant shock and it is adapting to the site. Furthermore,

the tree has only a very small leaf area at this time and

anything that interferes with the development of new foliage

will severely delay the growth of the seedling. Indeed, trees

in this study with infested terminals only in the first

4
Table 4-Relative impact of pine tip moth attack (RI) and RI weighted

by observed infestation level for each generation and

growing season

Year

Unweighted (RI) Infestation Weighted (RI)

Moth Full Reduced reduced

gen. model model TI PBI model

- -Percenf- -

1 1 0.23 0.40 12.1 - 0.12

2 0.07 0.13 43.5 - 0.13

3 0.00 0.08 65.6 - 0.12

2 1 0.22 0.16 69.2 45.8 0.27

2 0.16 0.09 52.2 43.1 0.11

3 0.12 0.05 49.2 28.1 0.07

3 1 0.19 0.09 72.4 63.3 0.17

generation had 1.72 annual growth flushes compared to

4.33 in uninfested trees. Infested trees in the first generation

also were significantly smaller (30.2 cm) at the end of the

year compared to unattacked trees (71 .O cm) or trees

attacked only in the second (50.7 cm) or third (55.6 cm)

generations.

The results of the analysis presented in table 4 suggest that

control of the first generation during the first year should be

a high priority. However, infestation levels during this

generation tend to be low because the tip moth population is

in the process of becoming established in the plantation.

Consequently, control of tip moth in the first generation will

affect only a small proportion of trees in the stand.

Therefore, since tip moth attack is not uniform within or

between years, an analysis of the relative impact weighted

by expected or observed infestation level is appropriate

(table 4). The greatest weighted impact occurred in the first

generation of the second and third growing seasons.

Accordingly, if these infestation levels are representative of

the temporal attack pattern which occurs in the first three

growing seasons, and if the cost of control is approximately

the same for each generation, then control of the first

generation in the second and third growing seasons should

be given the highest priority.

Impact of Pine Tip Moth Attack on

Loblolly Pine Volume

Impact of pine tip moth attack on pine volume is obtained by

adjusting the average height of the dominant and

codominant trees. The first step is to use the linked height

models to obtain predicted pine heights given a specified

level of tip moth attack. These heights are used to obtain the

reduction in height due to tip moth attack. This is done by

taking the difference between the predicted height without

tip moth attack (0 infestation) and the predicted height given

the specified levels of tip moth attack. The height of the

dominant and codominant pines is then adjusted based

upon the calculated reduction in height. The pine volume is

then calculated from the yield equations. This procedure

assumes that the growth impact due to tip moth attack at

age 3 will continue until age 15. This assumption has been

shown to hold true for loblolly pine attacked by the pine tip

moth in the southern U.S. (Hedden 1998).

The potential maximum reduction in height at age 3 using

the reduced model based upon 100 percent infested

terminals is 4 feet. Therefore, for this model, impact due to

tip moth attack could range from 0 to 4 feet. Table 5 shows

the reduction in total pine cubic foot volume (inside bark) per

acre at age 15 for pine densities of 400, 500, 600 and 700

trees per acre at age 5 with a site index (base age 25) of 70

feet. This table can be used to obtain an estimate of the

volume impact due to tip moth infestation for any calculated

reduction in height. In this study, the reduction in tree height

using the observed average percent infested terminals

(table 4) was 1.63 feet. This height reduction corresponds to

a reduction in total volume (inside bark) of between 180 and

204 cubic feet per acre at age 15 depending on the pine

density. This represents an approximate reduction in pine

volume per acre at age 15 of about 8 percent.

Table CL-Reduction in total pine cubic foot

volume (inside bark) per acre at age 15 for pine

densities of 400,500,600 and 700 trees per acre

at age 5 with a site index (base age 25) of 70 feet

Reduction Trees per acre

in height (ft) 400 500 600 700

0.0 0 0 0 0

0.5 101 110 122 130

1.0 197 215 239 253

1.5 289 316 349 371

2.0 376 412 454 483

2.5 458 504 552 589

3.0 536 591 645 689

3.5 609 674 731 784

4.0 677 752 812 872

5
This procedure can be used to calculate volume loss due to

tip moth attack for any combination of planting density, age,

or site index using the appropriate yield equations (Burkhart

and others 1972). Furthermore, this method of modifying the

average height of dominant and codominant trees can be

used to estimate losses due to tip moth attack using other

loblolly pine growth and yield models (Amateis and others

1984, Bailey and others 1985, Hafley and others 1982).

Economic Evaluation of Tip Moth Control

Decisions to control Nantucket pine tip moth should be

made by comparing the costs and benefits of control. The

benefits are the increases in wood yield at harvest due to a

reduction in tip moth damage. The costs are the financial

resources needed to reduce tip moth attack. An example of

an economic analysis of pine tip moth control showing both

the pertinent costs and benefits is described below. This

example will assess the economic feasibility of using loblolly

pine seedlings treated with an insecticide in the nursery to

reduce tip moth damage in the first tip moth generation after

planting.

Table 6 shows the estimated impact of pine tip moth

infestation on loblolly pine yield from moths attacking trees

during the first generation of the first growing season. Tip

moth attack causes a linear decline in pine pulpwood yield.

Also shown are the present values of the reduction in pine

yield for discount rates of 4 percent, 6 percent and 8 percent

due to moth attack. The insecticide treatment cost for pine

seedlings in the nursery is about $0.003 per seedling

(Doggett 1998) which amounts to $2.62 per acre if 875 trees

per acre are planted. The economic threshold (where the

costs equal the benefits) for Nantucket pine tip moth control

in the first generation of the first season are terminal

infestation levels of 3.9, 6.9 and 9.2 percent, respectively, for

the present values of 4, 6 and 8 percent. Since the observed

average terminal infestation level in the untreated plots for

the first generation in the first season was 12.1 percent,

nursery treatment in this example would have been cost

effective for the 4, 6 and 8 discount rates assuming that

complete control resulted from nursery treatment of the

seedlings. Cost effectiveness of controlling other tip moth

generations can be evaluated in a similar manner.

The type of analysis presented here allows the identification

of the infestation level associated with an economic

threshold in each tip moth generation. This information,

when used with methods for predicting expected tip moth

levels, will assist in the development of an economically

viable program for control of the Nantucket pine tip moth in

areas similar to the coastal plain of North Carolina.

CONCLUSION

The Nantucket pine tip moth has the potential to cause

significant growth loss in planted stands of loblolly pine in

Table 64mpact on NPV for attack in the 1st generation after

planting in a I!!-year-old pine stand SI 70 planted at 875 trees per

acre

Terminal Height DBH Pulpwood

Present value loss (%)

infestation loss loss loss 4 6 8

Percent Ft In. Cords _ _ _ _ _ _ Dollars _ _ _ _ _ _ _

0 0.00 0.00 0.0 0.00 0.00 0.00

5 0.08 0.03 0.2 3.33 2.50 1.89

1 0 0.16 0.07 0.3 5.00 3.75 2.83

1 5 0.24 0.10 0.5 8.34 6.26 4.73

20 0.32 0.13 0.7 11.66 8.76 6.62

25 0.40 0.16 0.9 14.99 11.27 8.51

30 0.48 0.20 1.1 18.32 13.77 10.40

35 0.56 0.23 1.2 19.99 15.02 11.35

40 0.64 0.26 1.4 23.32 17.52 13.24

45 0.72 0.29 1.6 26.65 20.03 15.13

50 0.80 0.33 1.7 28.32 21.28 16.08

55 0.88 0.36 1.9 31.65 23.78 17.97

60 0.96 0.39 2.1 34.98 26.29 19.86

65 1.03 0.42 2.2 36.65 27.54 20.80

70 1.11 0.45 2.4 39.98 30.04 22.70

75 1.19 0.49 2.6 43.31 32.55 24.59

80 1.27 0.52 2.7 44.98 33.80 25.53

85 1.35 0.55 2.9 48.31 36.30 27.43

90 1.43 0.58 3.0 49.97 37.55 28.37

95 1.51 0.62 3.2 53.30 40.06 30.26

100 1.59 0.65 3.3 54.97 41.31 31.21

6
the southern United States. The models relating tree height

to tip moth infestation level developed in this study show that

tip moth attack during the first generation of the year is

especially harmful, and that this generation is relatively easy

to control. These models also can be used to calibrate pine

growth and yield models to estimate the impact of this pest

on pine volume. Furthermore, the output on pine volume

loss due to tip moth attack can be used to economically

evaluate potential tip moth control programs.

ACKNOWLEDGMENTS

Data in this study were collected as part of a cooperative

project between Clemson University and Weyerhaeuser

Company to study pine resistance to tip moth attack. The

author thanks Weyerhaeuser for the their support.

REFERENCES

Amateis, R. L., Burkhart, H. E., Knoebel, 6. R., Sprinz, P T. 1984.

Yields and size class distributions for unthinned loblolly pine

plantations on cutover site-prepared lands. Virginia Polytech.

Inst. 8 State Univ., School of For. & Widl. Res., Publication

FWS-Z&Q,69 pp.

Bailey, R. L., Grider, G. E.. Rheney, J. W., Pienaar, L. V. 1985. Stand

structure and yields for site-prepared loblolly pine plantations in

the Piedmont and upper Coastal Plain of Alabama, Georgia, and

South Carolina. Univ. of Georgia COIL of Agric. Exp. Sta. Res.

Bull. 328, 118 pp.

Berisford, C. W. 1988. The Nantucket pine tip moth. Chapter 6 In:

A. A. Berryman, ed. Forest insect outbreaks: patterns, causes,

and management strategies. Plenum.

Burkhart, H. E., Parker, R. C., Strub, M. R., Oderwald, R. G. 1972.

Yields of old-field loblolly pine plantations. Virginia Polytech. Inst.

& State Univ., School of For. & Widl. Res., Publication FWS-3-72,

51 PP.

Cade, S. C., Hedden, R. L. 1989. Evidence for tip moth (Rbyacionia

frustrana) resistance in loblolly pine (Pinus faeda). pp. 137-144.

In: R.I. Alfaro and S.G. Glover, eds. Insects affecting reforestation: biology and damage. Forestry Canada, Victoria, B.C.,

Canada.

Doggett, C. A. 1998. Personal communication. NC Forestry Service,

Raleigh, NC.

Drooz, A. T. 1985. Insects of eastern forests. Misc. Publ. 1426.

USDA For. Serv., Washington, DC.

Hafley, W. L., Smith, W. D., Buford, M. A. 1982. A new yield

prediction model for unthinned loblolly pine plantations. Tech.

Rep. 1, So. For. Res. Center, NC St. Univ., Raleigh, NC.

Hedden, R. L. 1998. Impact of Nantucket pine tip moth attack on

loblolly pine-a southwide summary. pp 569-573. In: T. A.

Waldrop, ed. Proceedings of the tenth biennial southern

silvicultural conference, USDA For. Serv., So. Res. Sta.,

Asheville, NC, Gen. Tech. Rep. SO-20.

SAS, 1988. SASISTAT user’s guide, release 6.03 edition. SAS

Institute, Cary, NC. 1028 p.

Timber Mart-South. 1997. Stumpage price mart - standing timber,

SC 4th quarter 1997. Daniel B. Wamell School of For.

Resources, Univ. of Georgia, Athens, GA.

Van Deusen, P. C., Sullivan, A. D. and Matney, T. G. 1981. A

prediction system for cubic foot volume of loblolly pine applicable

through much of its range. South. J. Appl. For 5:186-189.
CTION OF FOREST MANAGEMENT PRACTICES AND TIP MOTH DAMAGE

John T. Nowak’

Abstract-intensive forest management practices have been shown to increase tree growth and shorten rotation time.

However, they may also increase the need for insect pest management because of higher infestation levels and lower action

thresholds. The Nantucket pine tip moth (Rhyacionia frustrana [Comstock]) is one insect that is expected to become more

important with more intensive forest management practices. Two studies were developed to investigate these relationships.

Treatments included various combinations of herbicide applications, irrigation, fertilization, and insecticide applications.

These studies demonstrated that tip moth management improves tree growth. Tip moth damage increased due to weed

control, but not due to N fertilization. Nitrogen fertilization did increase the number of tip moth pupae per shoot, however. In

conclusion tip moth populations can increase due to intensive management practices, and insect control should be

considered a part of efforts to maximize tree growth.

INTRODUCTION

The demand for forest products in the United States is

growing while the land base for producing these

commodities is shrinking as a result of conversions to other

uses, increased land fragmentation, and concerns about

endangered species and old growth forests, In order to meet

timber and fiber needs, commercial forests must be

managed more efficiently. Intensive management practices,

such as herbaceous weed control, irrigation, and fertilization

can increase tree growth and shorten rotation time (Pritchett

and Smith 1972, Haywood 1986, Zutter and others 1986,

Creighton and others 1987). Unfortunately, they may also

increase the frequency and severity of pest infestations

(Hedden and Nebeker 1984, Ross and others 1990). There

is a critical need for studies on the effects of intensive forest

management practices on pest insect populations.

Loblolly pine (Pinus taeda L.) is the most commercially

important tree species in the southeastern United States.

Several insects are associated with young stands of loblolly

pine and are likely to become more important as

management intensity increases. The Nantucket pine tip

moth (Rhyacionia frustrana [Comstock]), is one such species

(Sun and others 1998). Feeding by tip moth larvae can

decrease tree growth in the early years following stand

establishment (Warren 1964, Beal 1967, Lashomb and

others 1978, Berisford and others 1989). Tip moth infestation

levels often vary with intensity of silvicultural manipulations,

such as mechanical site preparation, herbaceous weed

control, and fertilization (Hertel and Benjamin 1977, White

and others 1984, Ross and Berisford 1990, Ross and others

1990). Miller and Stephen (1983) concluded that differences

in vegetation levels were not a good indicator of tip moth

damage. However, Ross and others (1990) found that

herbicide-treated plots had signicantly more tip moth

damage than control plots during the first two growing

seasons of a study conducted on the upper Coastal Plain of

Georgia. Pritchett and Smith (1972) showed significant

reductions in tip moth damage levels related to phosphorus

(P) and potassium (K) fertilization, but no differences were

observed after nitrogen (N) fertilization.

In January 1995, International Paper Corporation

established a study of loblolly pine at their Southlands

Experimental Research Forest near Bainbridge, GA to

determine the maximum growth potential of loblolly pine

using several hierarchies of cultural treatments. We

examined the pest problems associated with these

intensively managed loblolly pine within the first five years

following stand establishment. Our objectives were to

monitor insect pest establishment and to quantify insect

associated growth losses among the different silvicultural

treatments. A second study was established in 1999, near

Powelton, GA to further examine the effects of fertilization

and herbicide application on tip moth development and

infestation levels.

MATERIALS AND METHODS

Bainbridge Study

This study was conducted in Decatur County, GA, about 20

km south of Bainbridge. The soil type was classified as a

Wagram-troup complex and the site index was estimated to

be 59 (base age 25; loblolly pine) (Personal communication.

Tom Cooksey, Southlands Experiment Forest, International

Paper Corp., Bainbridge, GA, 31717). The main study area

was established on an old agricultural field that had been

used to grow soybeans and watermelon. The surrounding

plant community included a mixture of agricultural crop

lands, hardwood forests, and longleaf (Pinus palustris Mill.)

and loblolly pine forests of varying age classes.

A randomized complete block design with three blocks of

four treatments was established. Each treatment plot was

0.2 ha, and contained 216 1-O seedlings (grown for one year

in the nursery before being planted in the field) (12 rows of

18 seedlings) hand planted in January 1995. One row on the

end of each plot was designated as a border row and

1 Graduate Research Assistant, 413 Bioscience Building, University of Georgia, Athens, GA 30602.

Citation for proceedings: Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.

a
excluded from subsequent evaluations of insect infestation.

Four improved loblolly pine seed sources from a nursery in

North Carolina were blocked randomly within each plot.

site was subsoiled on 4 m centers and harrowed two m

prior to planting. Sulfometuron (Oust@) (0.28 kg [A&ha)

herbicide was applied once prior to planting and

glyphosphate (Accord@ 1.8 kg [All/ha) was applied twice

prior to planting and then monthly during the gro

season throughout the study to minimize herbaceous

weeds.

The treatments were herbaceous weed control (i-i), l-i c

irrigation (I), H + I + fertilization (F), and t-i + I f F + pest

control (P). In the original study design, the control treatment

was the H treatment. However, because weed control has

been shown to influence tip moth damage levels (

others 1990), we included three additional control plots in a

nearby stand that represented more typical forest

management. The control stand (C), approximately 250 ha in

size, was located <I km north of the main study site and

contained 1-O seedlings machine planted concurrently

the main study site. Except for a site preparation a~pl~c~tio~

of herbicides (Sulfometuron) and a prescribed bum

planting, competing vegetation was not managed in

stand. A number of factors besides weed control could

contribute to differences between the control

more intensively managed main study plots.

believe that these comparisons provide useful i~format~o

regarding the potential differences between ostensive

cultural practices and traditional forest management.

A dripline irrigation and fertigation (water and nutrients)

system (Netafim Irrigation, Altamonte Springs, FL) was use

to add water and nutrients. Water was pu

a nearby lake onto the treatments receivi

nightly interval at a rate of 18 cm per year.

applied to the treatments receiving fertilize

ha in 1995, 79 kg/ha in 1996, 133 kgiha i

ha in 1998 using an 8-2-8 liquid fertilizer forrn~~at~~~l.

Fertilizer applications were distributed evenly from

through November. Permethrin (Pounce@ 3.2 EC, F

Corporation, Philadelphia, PA) (1 .I kg [Ail/25 ha) a

acephate (Orthene@ 75 Turf, Tree and Ornamental, Valent

USA Corp.) (2.2 kg [Al]/78 liters) were applied separately

with backpack sprayers (Solo@, Newport News, VA) to the

H+I+F+P treatment throughout each growing season at

biweekly intervals in 1995-1997. Insecticide appiica~i~~~

were discontinued for the first seven months of 1998, but

were resumed in September. The insecticide treatrne~ts ha

been discontinued because of the large size of the trees a

the lack of tip moth in the previous two years.

Nantucket pine tip moth damage was evaluated three times

annually following the first, second, and combined third and

fourth generations. The third and fourth generations were

combined into one evaluation date because of considerable

damage overlap between these two generations (Berisf

and others 1992). Evaluation dates were timed nc

with either the tip moth pupal stage or just after

emergence (Ross and Berisford 1990). Forty trees per

treatment per block were randomly selected on each

evaluation date. All shoots were examined for tip moth

damage during each evaluation in 1995-l 997. However, due

to the size of the trees in 1998, only the terminal and top 2

branch whorls were examined. There is a significant

correlation between terminal and top whorl damage and

whole tree damage (Fettig and Berisford 1999). Damage

was recorded as the percentage of damaged shoots: a shoot

was defined as an apical meristem containing at least 5 cm

of foliage.

Basal diameter and total height were measured following

each growing season. For comparative purposes, a tree

stem volume index was calculated by multiplying the square

of the basal diameter times height (D’H). This volume index

has been shown to correlate well with above-ground

biomass (Hatchell and others 2 985).

The control treatment means for insect damage

qualitatively compared to the combined means of the main

study area because the control area was s

differences, statistical co

the main study site and t

implications for insect po~~lat~o~ dynamics.

This study was conducte

Powelton in 1999. A ~afl~omiz~

eatmerits were

The herbicide and fertilizer treatments were applied on 5

May and 21 July. The N fertilizer was applied at a rate of 107

kg/ha of elemental N in the form of 46 percent elemental

urea. ~lyphosp~at~ (Accord@ 1.8 kg [All/ha) was applied

with backpack sprayers (Solo@,

Treatment trees were covered with plastic bags for ~15 min

during herbicide application because glyphosphate is

activite on pine trees.

Twenty-five trees per treatment per block were randomly

selected on each evaluation date. Tip moth damage was

evaluated on a whole tree basis three times annually

following each of the three generations in a manner

consistent with the Bainbridge study. Fifty tip moth infested

shoots per treatment per block were collected near the end

of the third generation and returned to the laboratory for

examination. For each shoot, length of tip moth damage,

number of insects, and life stages present were recorded.

Tip moth infestation percentages were arcsine square root

transformed and subjected to an analysis of variance

(ANOVA) by each evaluation date. The insect damage data

9
are reported as the non-transformed means. Tree growth

data were compared by ANOVA for each evaluation date.

Insect damage and growth treatment data were analyzed as

a randomized complete block design and means were

separated using Proc GLM and Tukey’s Studentized Range

Test (SAS Institute 1988).

RESULTS

Bainbridge Study

Tip moth damage levels exceeded 10 percent only twice

during this study, in ‘l995 and 1998 (fig. ?). Tip moth

damage reached moderate levels in the third and fourth

generation of 1995 and then dropped below 3 percent in

1996 and 1997 in the main study area. At the end of 1998,

tip moth damage was ca. 80 percent in the main study area.

Damage in the control treatment never exceeded 30

percent, even when damage was relatively high in the main

study area.

No significant differences were detected in tip moth damage

among the H, H+I, and H+I+F treatments in any year (P >

0.05; Tukey test) and these treatments are combined for

analysis (fig. 1). Percent damage was significantly higher for

these treatments than the H+I+F+P treatment during the

highest infestation periods (generations 3 & 4 in October

1995 (F = 25.46; d.f. = 3,6; P = 0.0008) and October 1998

80

I

70 -

u)

ii

* 60-

ii

u

$j) 50-

E 40-

P

a

tiZ?ZB Control

0 Main Study Area

hzzl H+I+F+P

10

0, ,

‘_

I

Figure I-Mean percent (+/-SE) of loblolly pine shoots damaged by

Nantucket pine tip moth during ‘1995-1998 in Bainbridge, GA. Three

treatments means [herbicide (H), H + irrigation (I), and H + I +

fertilizer (F)] are classified as the Main Study Area for simplicity and

the lack statistical differences (P > 0.05;Tukey test). Bars with the

same letter for each sample date are not significantly different (n =

480; P > 0.05; Tukey test). Control means (n = 120) are provided for

comparative purposes only and are not included in the statistical

analysis.

(F= 13.55; d.f. = 3,6; P = 0.0044)) (fig. 1). However, at lower

damage levels, no significant differences were found. Tip

moth damage levels were noticeably higher in the main

study area than in the control area during the periods of

highest infestation (fig. 1). There were no significant

differences in tip moth damage levels among the four

different seed sources used in the main study area (P z

0.05).

Significant differences were observed in height and volume

among all treatments during 1995 and 1996 (figs. 2 and 3).

The H+l+F+P treatment had significantly greater height and

volume measurements than the other treatments at the end

of 1995, 1996, and 1998. In 1997, there was no significant

difference in height between the H+I+F treatment and the

H+I+F+P treatment (fig. 2), but the H+I+F+P treatment had a

significantly greater volume index (fig. 3). There was no

significant difference in height between the H+I and H+I+F

treatments in 1998, but the H+I+F treatment had a

significantly higher volume index (fig, 3). The control

treatment had the lowest values for height and volume

measurements throughout the study (figs. 2 and 3).

Poweiton Study

Tip moth damage ranged between 16 and 39 percent (fig. 4).

There were no treatment differences in the second tip moth

generation. However, significant differences were detected

with ANOVA within treatment for percent tip moth infestation

(F = 5.03; d.f. = 3,6; P = 0.0446), number of pupae per shoot

(F = 13.66; d.f. = 3,6; P = 0.0043), and tree diameter (f =

800

600

mim Control

-H

hz11 H+I

missi H+I+F

EXE H+I+F+P

a

a

1995 1996 1997 1998

Figure 2-Mean tree height (+/-SE) for four growing seasons in a

study conducted in Bainbridge, GA, following yearly cultural

treatments: Herbicide (H), H + irrigation (I), H * I + fertilizer (F), and

H + I + F + pest control (P). Bars with the same letter are not

significantly different (n = 480; P > 0.05; Tukey test). Control means

(n = 120) are provided for comparative purposes only and are not

included in the statistical analysis.

I O
ermm Control

- H

- H+I !----A m H+I+F

-H+I+F+P

a

d

f

a

1997 1998

Figure 3---Mean tree volume index (+/-SE) (basal diameter-squared

times height) for four growing seasons in a study in Bainbridge, GA

following yearly cultural treatments: Herbicide (H), H + irrigation (I),

H + I + fertilizer (F), and H + I + F + pest control (?). Bars with the

same letter are not significantly different (n = 480; P > 0.05; Tukey

test). Control means (n = 120) are provided for comparative

purposes only and are not included in the statistical analysis.

5 0

4 0

u)

Ii

i %

-0 3 0

iii2

2

m

pE 2 0

8

t

n.

IO

0

a

a b T

Control N-Fert Herb Herb-N Control N-Fert Herb Herb-N

Figure 4-Mean percent (+/-SE) of loblolly pine shoots damaged by Figure 5-Mean number of tip moth pupae per shoot (+/-SE) for the

Nantucket pine tip moth during the third tip moth generation of 1999 third tip moth generation in a study conducted in Powelton, GA,

in a study in Powelton, GA following cultural treatments: control, N following cultural treatments: control, N fertilization (N-fert),

fertilization (N-fert), herbicide (Herb), and herbicide application and herbicide (Herb), and herbicide application and N fertilization (HerbN fertilization (Herb-N). Bars with the same letter for each sample N). Bars with the same letter are not significantly different (n = 300;

date are not significantly different (n = 240; P > 0.05; Tukey test). P > 0.05; Tukey test).

10.42; d.f. = 3,6; P = 0.0086) at the end of the third

generation. Tip moth damage was significantly higher in the

Herb-N and Herb treatments than in the control treatment

(fig. 4). Mean number of tip moth per shoot ranged between

0.33 and 0.78 (fig. 5). There were significantly more pupae in

the Herb-N treatment than in any of the other treatments, but

none of the other treatments varied statistically (fig. 5). Mean

tree diameter was significantly greater in the Herb and HerbN treatments than in the N-fen and control treatments, which

did not differ significantly (fig. 6). However, there was no

treatment difference in tree height (F = 1.97; d.f. = 3,6; P =

0.2205).

DISCUSSION

Tip moth damage in the Bainbridge study was at the highest

level after the trees had exceeded what is normally

considered susceptible size (Berisford 1988). Because of the

absence of significant tip moth infestation after the 1995

growing season, it was thought that the trees in the more

intensive treatments may have simply outgrown their

susceptibility to attack in the first growing season. However,

the high tip moth damage in 1998 dispelled this hypothesis.

It was thought that perhaps the pitch pine tip moth (I?.

rigidana [Fernald]) was causing the infestation in 1998

because R. rigidana are more common in taller trees than R.

frusfrana (Berisford 1988). However, the moths were

identified as R. frusfrana based on Yates’ (1967) key.

In the Bainbridge study, tip moth infestation levels fluctuated

more in the main study area without competing vegetation

than in the control area with competing vegetation. Similar

fluctuations were found by Miller and Stephen (1983) where

0.8

b

b

a

11
0

Control N-Fert Herb Herb-N

Figure 6-Mean tree diameter (+/-SE) for the third tip moth

generation in a study conducted in Powelton, GA, following cultural

treatments: control, N fertilization (N-fert), herbicide (Herb), and

herbicide application and N fertilization (Herb-N). Bars with the

same letter are not significantly different (n = 240; P > 0.05; Tukey

test).

tip moth damage levels fluctuated more in areas with low

competing vegetation than in areas with high vegetation

levels. Tip moth population levels in areas with competing

vegetation appear to be more stable than populations in

areas without competing vegetation. One possible reason for

this could be that the tip mot natural enemy complex exerts

a more consistent influence in areas with herbaceous

weeds perhaps because of a more favorable microclimate

and the presence of food sources such as pollen and nectar

(Pimentel 1961, Strong 1984). In a previous study, total

parasitism was higher in areas with competing vegetation

than in adjacent areas with significantly less vegetation

(McCravy and Berisford In press). However, parasitism data

were not collected in this study.

Irrigation and fertilization significantly increased tree growth,

but did not affect tip moth infestation levels. In a greenhouse

study, Ross and Berisford (1990) concluded that

management practices that increase water and nutrient

availability to lobiol~y pine increase the amount of tip moth

infestation. Results of the fertilization treatments are

consistent with other studies concerning the effects of

fertilization on tip moth infestation levels (Pritchett and Smith

1972, Berisford and others 1989). However, none of these

studies, including this one, accounted for the number of tip

moth larvae or pupae ndividuai shoot. Ross and

Berisford (1990) foun t pupal densities were signi~cantly

higher in potted seedlings with high nutrient levels.

intensive studies are needed to investigate the effects of

fertilization on the amount of tip moth attacks and

1 2

subsequent infestation. If N fertilization increases tip moth

infestation, it might not be economically feasible to apply

fertilizer if growth gains were lost to insect infestation. On the

er ha it is possible that fertilization could be used to

rease e vigor and thereby reduce the impact of tip

th infestation.

l- o~e~ton study was designed to further evaluate the

effects of fe~~lizatio~ and weed control on tip moth damage

levels ~eve~o~rnent. It has been shown that a reduction

tation can lead to an increase in tip moth

lier and Stephen 1983, Ross and others

1990). However, the Bainbridge study did not adequately

address this issue because a true control was not included

in o~igi~al study design. In the Powelton study, herbicide

w ations reduced competing vegetation and

s u quently increased tip moth damage. Herbicide

applications coupled with N fertilization also increased the

n u er of pupae per shoot. This indicates that intensive

ent practices such as herbaceous weed

control can increase tip moth populations and subsequent

damage.

In the Powelton study, we found that fertilization alone did

not increase tip moth damage or the number of pupae

present per shoot. However, there were also no differences

in tree height or diameter due to N fertilization. The Powelton

study has only lasted one year and tip moth damage

estimates were only recorded in one generation after the

plots were treated. lit is possible that the trees and also the

insects have not had time to respond the N fertilization. The

Powelton study will continue for three more generations and

foliar analysis will be performed. It is too early in the

experiment to conclude that N fertilizer will not have an

effect on tip moth damage levels or on insect development in

contrast to Ross and Berisford (1990).

applications increased tree growth 27 percent

+l+F treatment even though tip moth infestations

bridge study were low compared to many other

ashomb and others 1978, Miller and Stephen

1983, Ross and others 1990). In 1998, the insecticide

applications were discontinued because of low insect

infestation in the previous two years. The applications were

resumed once heavy damage began to reappear in

September of 1998. Therefore, tip moth infestation in the

pest control plots was significantly lower than the other

treatments, but could have been even lower if insecticide

applications had been made in a manner consistent with

previous years. It has been argued that growth losses due to

infestation are transitory (Williston and Barras

owever, this was not evident in our four year study.

Future growth measurements are intended. Longer-term

studies have shown that growth increases due to tip moth

management are maintained (Cade and Hedden 1987,

~np~~bl~shed data. Wayne Berisford, Department of

~~t~mology, University of Georgia, Athens, GA, 30602).

In ctusion, intensive forest management practices such

a s baceous weed control and N fertilization can in some

cases exacerbate tip moth problems and may disrupt tip

moth population dynamics. However, tip moth control can

reduce grow losses associated with feeding damage.
ACKNOWLEDGMENTS

The author thanks Tom Cooksey (International Paper

Corporation) for his assistance throughout this study. The

author also thanks the following people for help in data

collection and technical help: Chris Asaro, Anthony Coody,

Charles Gasset, Richard Garland, Mitch Gibbs, Nick LeCroy,

and Joe Petty (University of Georgia). The author is also

grateful to International Paper Corporation and the Timber

Company for providing access to research sites. This

research was supported in part by funds from the USDA

Forest Service, Southern Research Station, and the

University of Georgia Pine Tip Moth Research Consortium.

REFERENCES

Beal, R. H. 1967. Heavy tip moth attacks reduce early growth of

loblolly and shortleaf pine. USDA. Forest Service Research Note

SO-54. New Orleans, LA: U.S. Department of Agriculture, Forest

Service, Southern Forest Experiment Station.

Berisford, C. W. 1988. The Nantucket pine tip moth. In: Berryman,

A. A., ed. Dynamics of Forest Insects: patterns, causes, and

implications. New York: Plenum Publishing Corporation:

141-161.

Berisford, C. W.; Canalos, C. G.; Godbee, J. F. Jr.; Yates, H. 0. Ill.

1992. Occurrence and seasonal activity of pine tip moths in

Georgia. Georgia Forestry Research Paper No. 87. Macon, GA:

Georgia Forestry Commission. 11 p.

Berisford, C. W.; Godbee, J. F. Jr.; Ross, D. W. 1989. Impact of pine

tip moth control, weed control, and fertilizer on growth and form

of loblolly pine. In: Alfaro, R. I.; Golver, S. G. eds., Insects

Affecting Reforestation: Biology and Damage. Proc. IUFRO

Working Group, Insects Affecting Reforestation. Forestry

Canada, Pacific Forestry Centre, Vancouver, BC, Canada:

130-136.

Cade, S. C.; Hedden, R. L. 1987. Growth impact of pine tip moth on

loblolly pine plantations in the Ouachita Mountains of Arkansas.

Southern Journal of Applied Forestry. 11: 128-133.

Creighton, J. L.; Zutter, B. R.; Glover, G. R.; Gjerstad, D. H. 1987.

Planted pine growth response to herbaceous vegetation control,

treatment duration, and herbicide application technique.

Southern Journal of Applied Forestry. 11: 223-227.

Fettig C. J.; Berisford, C. W. 1999. Nantucket pine tip moth phenology in eastern North Carolina and Virginia: implications for

effective timing of insecticide applications. Southern Journal of

Applied Forestry. 23: 30-38.

Hatchell, G. E.; Berry, C. R.; Muse, H. D. 1985. Nondestructive

indicies related to above-ground above biomass of young loblolly

and sand pines on ectomycorrhizal and fertilizer plots. Forest

Science. 31: 419-427.

Haywood, J. D. 1986. Response of planted Pinus taeda L. to brush

control in northern Louisiana. Forest Ecology and Management.

15: 129-134.

Hedden, R. L.; Nebeker, T. E. 1984. Integrated pest management in

pine stands (O-5 years) Insects. In: Branham, S. J.; Hertel, G. D.

eds., Proc., Intergrated Forest Pest Management Symposium.

University of Georgia Center for Continuing Education, Athens,

GA. 39-53.

Hertel, G. D.; Benjamin, 0. M. 1977. Intensity of site preparation

influences on pine webworm and tip moth infestations of pine

seedlings in North-central Florida. Environmental Entomology. 6:

118-122.

Lashomb, J. H.; Steinhauer, A. L.; Douglass, L. 1978. Impact studies

of Nantucket pine tip moth populations on loblolly pine. Environmental Entomology. 7: 910-912.

Miller, F. D., Jr.; Stephen, F. M. 1983. Effects of competing vegetation on Nantucket pine tip moth (Lepidoptera: Tortricidae)

populations in loblolly pine plantations in Arkansas. Environmental Entomology. 12: 101-I 05.

McCravy. K. W.; Berisford, C. W. [In press]. Effects of vegetation

control on parasitoids of the Nantucket pine tip moth, Rbyacionia

frusfrana (Lepidoptera: Tortricidae). Florida Entomologist.

Pimentel, D. 1961. Species diversity and insect population outbreaks. Annals of Entomological Society of America. 54: 76-86.

Pritchett, W. L.; Smith, W. H. 1972. Fertilizer responses in young

pine plantations. Soil Science Society of America Proceedings

36: 660-663.

Ross, D. W.; Berisford, C. W. 1990. Nantucket pine tip moth

(Lepidoptera: Tortricidae) response to water and nutrient status

of loblolly pine. Forest Science. 36: 719-733.

Ross, D. W.; Berisford, C. W.; Godbee, J. F. Jr. 1990. Pine tip moth,

Rhyacionia spp., response to herbaceous vegetation control in

an intensively site-prepared loblolly pine plantation. Forest

Science. 36: 1105-1118.

SAS Institute, Inc. 1988. SASlSTAT guide for personal computers,

Version 6.03 ed. SAS Institute, Inc., Cary, NC. 1028 p.

Strong, D. R. 1984. Banana’s best friend. Natural History. 93: 50-57.

Sun, J.; Kulhavy, D. L.; Yan, S. 1998. Prediction models of Nantucket

pine tip moth, Rhyacionia frustrana (Cornstock) (Lepidoptera:

Tortricidae) infestation using soil and tree factors. Journal of

Applied Entomology. 122: 1-3.

Warren, L. 0. 1964. Growth of pine trees protected from attack by

Nantucket pine tip moth. Arkansas Agricultural Research

Station, Arkansas Farm Research 13: 11.

White, M. N.; Kulhavy, D. L.; Conner, R. N. 1984. Nantucket pine tip

moth (Lepidoptera: Tortricidae) infestation rates related to site

and stand characteristics in Nacogdoches county Texas.

Environmental Entomology 13: 1598-1601.

Williston, H. L.; Barras, S. J. 1977. Impact of tip moth injury on

growth and yield of I6-yr-old loblolly and shortleaf pine. USDA

Forest Service Research Note SO-221. New Orleans, LA: U.S.

Department of Agriculture, Forest Service, Southern Forest

Experiment Station. 5 p.

Yates H. 0. Ill. 1967. Pupae of Rhyacionia frustrana, R. rigidana,

and R. subtropica (Lepidoptera: Olethreutidae). Annals of

Entomological Society of America. 60: 1096-I 099.

Zutter, B. R.; Glover, G. R.; Gjerstad, D. H. 1986. Effects of herbaceous weed control using herbicides on a young loblolly pine

plantation. Forest Science. 32: 882-899.

1 3
EVALUATION OF CANDIDATE INSECTICIDES FOR CONTROL OF THE

NANTUCKET PINE TIP MOTH (LEPIDOPTERA:TORTRIClDAE)

Mark J. Dalusky and C. Wayne Berisford’

ABSTRACT-Initial screening in 1995 compared the effkcacy of Capture@, Dimlin@,, Foray@, Mimic@, Neem@ Pounce@,

and Tempo@ in controlling infestation by the Nantucket pine tip moth, Rhyacionia frustrana (Comstock). Orthene@TTO,

Tame@ and a tank-mix of the two were added to the trials in 1996. All compounds tested were significantly better than the

check regarding infestation of terminal and top whorl shoots by Nantucket pine tip moth. All sprays were timed for a contacttype insecticide, unless otherwise stated, following the methods of Berisford and others (1984) using degree-day

accumulation triggered by male moth flight. In the Piedmont, the pyrethroids Tempo@, Capture@ and Pounce@ and the

insect growth regulator (IGR) Mimic@ performed best with Dimlin@, Neem@ and Foray@ being somewhat less effective. Test

results from the Alabama Coastal Plain were similar with Foray@ joining the top group. In 1996, Neem@ and DimlinQ were

dropped in favor of Orthene@ and Tame@ alone and in combination. All treatments in the Coastal Plain and Piedmont tests

were significantly better than control plots. Only two sprays (1 of Foray@ and 1 of Orthene@ applied on a contact timing)

failed to limit infestation in the top whorl below 10 percent. On an epidemic Virginia site, all treatments were significantly

better than controls with the pyrethroids. Orthen&/Tame mixtures and Foray@ plus a UV screen grouping together followed

by the various tank-mixes and Foray@ minus the UV screen. In 1997, Warrior@, a pyrethroid, was tested against third and

fourth generation tip moth in the upper Coastal Plain of Georgia. Top whorl infestation was held below 5 percent for both

generations compared to a mean of 30 percent for Pounce@. In 1998, Imidan, an organophosphate, was tested at 2 rates

for control of second generation Nantucket pine tip moth on a Piedmont site near Athens, GA. Control was excellent being

at or near zero percent infestation in treatment plots.

INTRODUCTION

Historically, chemical control of the Nantucket pine tip moth

(NPTM) has been accomplished by calendar sprays every 2

weeks beginning in spring and continuing through fall.

Timing of insecticide applications based on degree-day

driven models (Garguillo and others 1985, Fettig and others

1999) has both improved effectiveness and dramatically

reduced the number of sprays required to achieve

satisfactory control. Initial efficacy testing was conducted

with dimethoate, acephate (both organophosphates) and

then with fenvalerate, a synthetic pyrethroid (Berisford and

others 1984, Garguillo and others 1985). Clarke and others

(1990) and DeBarr (1982) suggested that repeated spraying

with fenvalerate and azinphosmethyl in a seed orchard

setting induced secondary scale outbreaks that reached

epidemic proportions in some cases. Some broad-spectrum

insecticides are toxic to tip moth natural enemies (McCravy

and others 2001) and may worsen tip moth infestations

when poorly timed. Recent regulatory actions taken by the

U.S. Environmental Protection Agency, most notably the

review of carbamate, chlorinated hydrocarbon and

organophosphate based insecticides under the Food Quality

Protection Act, has reduced the number of compounds

available and threatened the continued existence of several

forestry-use labels, due to their minor-use designation. With

this last trend in mind, we undertook to screen some new

and old compounds for efficacy in controlling tip moth

infestation in loblolly pine plantations.

METHODS

We began initial screening of potential tip moth control

chemicals in 1995 which compared the efficacy of Capture@

(FMC Corp.), Dimilin@ (Uniroyal), Foray@ (Abbott Labs),

Mimic@ (Rohm and Haas Co.), NeemB (Phero Tech Inc.),

Pounce@ (FMC Corp.) and Tempo@ (Bayer Corp.) in

controlling infestation by NPTM (table 1). Neem@ and

DimlinB were dropped in favor of Orthene TT08, Tame@

and a combination of the two (Valent USA) in 1996. The

1995 and 1996 trials were conducted in the Coastal Plain of

Alabama in Escambia and Monroe Counties and in the

Piedmont Plateau in Oglethorpe County near Lexington, GA.

A group trial was also conducted in an epidemic population

of tip moth in loblolly pine in southern Virginia in

Southhampton County near Emporia, VA. during the fall of

1996. In 1997, Warrior@ (Zeneca Ag Products), a pyrethroid,

was tested against third and fourth generation tip moth in the

upper Coastal Plain in Burke County near Waynesboro, GA.

In 1998, Imidan@ (Gowan Co.), an organophosphate, was

tested at two rates for second generation tip moth control on

a Piedmont site near Athens, GA.

All sprays were timed for a contact-type insecticide, unless

stated otherwise, following the method of Garguillo and

others (1985) revised by Fettig and others (1999) using

degree-day accumulation triggered by male moth flight. The

basic experimental design was similar for all tests regardless

of location or year. Trials consisted of randomized complete

blocks with 4-6 replicates of 8-l 0 tree plots. All compounds

were applied in water with Solo @ hand-pump sprayers.

1 Dalusky, Research Coordinator, Department of Entomology, University of Georgia, Athens, Georgia 30602; and Berisford, Professor of

Entomology

Citation forproceedings: Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.

1 4
Table l-Products tested for control of Nantucket pine tip moth:l995-1998

Product Percent A.I. Active Label

(formulation) Class applied Label rate ingredients statusa

Capture (2EC) Pyrethroid 0.025 8-12 ozlac Bifenthrin None

Pounce (3.2EC) Pyrethroid 0.024 4-8 ozlac Permethrin Full

Tame (2.4EC) Pyrethroid 0.025 8-16 oz/ac Fenpropathrin Partial

Tempo (2s) Pyrethroid 0.008 6-8 ozlac Cyfluthrin Partial

Warrior (1 EC) Pyrethroid 0.016 Lambda0.032 3.2-5.12 ozlac cyhalothrin 24C

lmidan (70WP) Organo- 2.0

phosphate 4.0 1.33 IblAc Phosmet Partial

Orthene TTO Organo-

(78%WP) phosphate 1.1 0.05-I jb/ac Acephate Partial

Foray (48B) Bacterial NA 0.125-I gal Bacillus

per acre thuringiensis Full

Mimic (2F) Insect

growth

regulator 0.014 8.0 oziac

(0.12lb.) Tebufenozide Full

a full= full EPA label for both pest, crop, and application technique; partial = either pest, crop, or application labeled but not all three; and

24C = special local need state label.

Water was pH adjusted to 5.5 for Orthene@ and ImidanQ

applications on recommendations by technical

representatives of the manufacturers . Pines were sprayed

with a fine mist until the foliage was visibly wet but not until

run-off. Mixing rates were extrapolated from existing labels

or were supplied by technical reps (see table 1 for list).

Frequently, in large group tests, all compounds were applied

on the same date which may not have been the optimum

date for a particular chemical. This was necessary due to the

logistics of traveling to sites with sufficient NPTM infestation

to make testing worthwhile. When NPTM damage was

readily visible, the number of infested shoots in the top whorl

(Fettig and Berisford 1999) were recorded for all treatments

and untreated controls. Typically, the percent infestation in

the terminal and top whorl shoots was analyzed via ANOVA

at alpha=0.05. Means were separated with a Tukey test for

all pairwise multiple comparisons or the non-parametric

ANOVA on ranks with means separated by StudentNewman-Keuls method when assumptions of normality and

equal variances were not met (SigmaStat Version 2.03,

SPSS Inc. 1997).

Experiment 1: Spring/Summer 1995

Initial screening compared the efficacy of Capture@ 2EC,

Dimlin@, Foray@ 48B, Mimic@ 2F, Neem@, Pounce@ 3.2EC

and Tempo@ 2s for control of second generation NPTM

infestation. Testing was conducted during late spring and

early summer in the Alabama Coastal Plain and in the

Piedmont region of Georgia. Neem@ and Dimlin@ were

dropped from subsequent testing in favor of Orthene@ and

Tame@.

Experiment 2: Spring/Summer 1996

Group testing was performed during the first generation of

moths in the Alabama Coastal Plain and in the upper

Coastal Plain of Georgia. An additional test was conducted

for third generation control in southern Virginia on an upper

Coastal Plain site experiencing an epidemic tip moth

infestation. Orthene@ TTO (78 percent WP), an

organophosphate, and Tame@ 2.4EC, a pyrethroid, alone

and in combination were added to the tests this year. On the

Georgia and Virginia sites, a two-spray regime of these

products was also evaluated. The second application

occurred ea. 8 days after the initial spray. Combination

sprays of Orthene@ and Tame@ were dropped from testing

in 1997.

Experiment 3: Spring/Summer 1997

Group testing was limited to two sprays in the Alabama

Coastal Plain during the first tip moth generation. Foray@,

Mimic@, Orthene@ TTO, Pounce@ and Tame@ were selected

for testing based on demonstrated efficacy and interest in

continued testing by the companies involved. The two spray

dates (160 and 190 degree-days centigrade) were dictated

by adverse weather in the Brewton area. and they occurred

15
before the optimum predicted pyrethroid spray date (237

degree-days centigrade). This unfortunate circumstance

allows us to draw conclusions concerning timing of spray

applications only as they relate to the predicted optimum

pyrethroid spray date. During the third and fourth generation

of moths in the upper Coastal Plain of Georgia, Warrior@

1 EC (a pyrethroid new to NPTM control) was evaluated with

Pounce@ included as a standard for comparison.

Experiment 4: Summer 1998

This test evaluated the efficacy of two rates of Imidan@

70WP (an older organophosphate) for control of second

generation moths on a Georgia Piedmont site near

Lexington, GA. Pounce@ was included as a standard for

comparison.

RESULTS AND DISCUSSION

Experiment 1 (I 995):

Tip moth populations were moderate at the Coastal Plain

site in Alabama with 45 percent of top whorl shoots infested

on check trees. In the Georgia Piedmont, the population was

somewhat lower with 33 percent of top whorl shoots

infested. At this test site, the pyrethroids, Tempo@, Capture@

and Pounce@ and the insect growth regulator (IGR) Mimic@

performed best with Dimlin@ NeemB and Foray@ being

somewhat less effective (table 2). Test results from the

Coastal Plain site were similar with Foray@ joining the group

of most effective treatments. All treatments were significantly

better than controls at both sites (F=8.36, PcO.0001, n=5,

df=7 for Alabama Coastal Plain site; F=10.4, P<O.OOOl, n=5,

df=7 for Georgia Piedmont site).

Experiment 2 (1996):

Tip moth populations in the Alabama Coastal Plain and

Georgia upper Coastal Plain sites were low, ranging from 24

percent to 27 percent. All treatments significantly reduced

damage compared to checks (F= 6.33, P~O.0001, n=5, df=8)

at both sites (table 3). Capture@, Pounca@, Tempo@,

Orthene@/Tame@ mix, Mimic@, Foray@ and Orthen& alone

(timed for a systemic) performed well. Only 3 sprays (1 of

Foray@ and 2 of Orthen& applied on a contact timing)

failed to contain infestation in the top whorl below 10

percent. We feel that tip moth pressure was not high enough

to provide a rigorous test of efficacy on this site. However in

Virginia, tip moth populations were at epidemic levels with

infestation in the top whorl above 65 percent. Again, all

treatments significantly reduced damage level below that of

the check plots (F= 11.3, P<O.OOl, n=4, df=lO) (table 4).

Capture@ out-performed both Orthen& applications as well

as the initial Orthene@Tame@ mix. All other treatments were

not significantly different although there was a trend for

Capture@ and Tempo@ to provide more protection than the

remaining treatments. Considering the high tip moth

incidence and the asynchronous nature of third generation

life stages, all treatments performed well.

Experiment 3 (1997):

In the Alabama Coastal Plain, populations of NPTM were

again low ranging from 26 to 33 percent of top whorl shoots

on check plots. Spray date 1 occurred on March 3 at 160

degree-days (centigrade), and spray date 2 on March 8 at

190 degree-days. The optimum predicted value from Fettig

and others (1999) is 237 degree-days. All treatments were

significantly different from untreated control plots regarding

Table 2-Mean percent top-whorl and terminal shoot infestation for group

testing in 1995

Product

Experiment 1: AL Coastal Plain Experiment 1: GA Piedmont

Top whorl Terminal Top whorl Terminal

Capture

Tempo

Pounce

Foray

Mimic

Neem

Dimlin

Check

10.5 aa

10.8 a

12.9 a

13.4 a

17.9 ab

25.3 b

29.0 c

45.0 d

10.0 a

27.5 ab

15.0 ab

22.5 ab

22.5 ab

44.4 b

40.0 b

72.5 c

3.8 a

2.2 a

6.6 ab

19.1 ab

7.3 ab

19.8 b

18.0 ab

34.3 c

5.0 a

5.0 a

20.0 ab

38.6 b

15.0 ab

36.4 ab

27.5 ab

70.0 c

aMean~ in columns with different letters are significantly different; alpha = 0.05.

1 6
Table 3-Mean percent top-whorl and terminal shoot infestation for group

testing in 1996

Experiment 2: AL Coastal Plain Experiment 2: GA Piedmont

Product Top whorl Terminal Top whorl Terminal

Capture 4.0 aa 3.0 a 0.0 a 0.0 a

Tempo 1.4 a 0.0 a 1.1 a 0.0 a

Pounce 5.2 a 3.0 a 0.8 a 0.0 a

Foray 2.8 a 7.0 a 5.6 ab 3.4 a

Foray plus UV 6.6 a 3.0 a 9.6 b 20.6 b

Mimic 5.0 a 7.0 a 2.4 ab 4.0 a

Orthene 10.0 a 7.0 a 11.1 b 16.8 b

Orthene II NA NA 3.1 ab 10.2 b

Orthene/ tame 6.0 a 3.0 a 6.7 ab 4.0 a

Orthene/tame II NA NA 3.5 ab 6.6ab

Check 24.0 b 23.0 b 26.9 c 50.0 c

a Means in columns with different letters are significantly different at alpha = 0.05.

Table 4-Mean percent top-whorl and terminal shoot

infestation for group testing in 1996

Experiment 2: VA Coastal Plain

Product Top whorl shoots

Capture

Tempo

Pounce

Foray

Foray plus UV

Mimic

Orthene

Orthene II

Orthene/Tame

Orthene/Tame II

Check

13.8 aa

18.3 ab

23.5 ab

31 .O ab

24.2 ab

24.0 ab

35.7 b

32.5 b

35.0 b

27.3 ab

64.5 c

a Means in columns with different letters are significantly different

at alpha=0.05

top whorl infested shoots (F=l9.2, P<O.OOl, n=4, df=5)

(table 5). Infestation levels were held below IO percent in top

whorl shoots except for a Tame@ application on spray date

2. Orthene@ Mimic@, and Foray@ all of which are thought to

have optimum spray dates occurring after the predicted

pyrethroid date, showed good residual efficacy based on

their early application dates. Mild temperatures during the

early spring and reduced UV incidence due to the oblique

angle of the sun may contribute to this apparent increase in

residual efficacy. Applications made later in the year may not

demonstrate this phenomena. In efficacy tests conducted in

the upper Coastal Plain of Georgia during the third

generation of NPTM, Warrior@-treated plots had less than 2

percent infestation in top whorl shoots compared to 4

percent for Pounce@ and 26 percent for the untreated

controls (F=51.2,Pc0.001, n= 4, df=2) (fig. 1). Fourth

generation control was excellent given the strongly

asynchronous nature of tip moth brood at this time of year,

plus the fact that the application rate for Warrior@ was

inadvertently cut in half (fig. 2). Infestation level was held to 4

percent in top whorl shoots compared with 18 percent for

Pounce@ and 35 percent for untreated controls (F=18.7,

P<O.OOl, n=5, df=2).

1 7
Table C&-Mean percent top-whorl and terminal shoot infestation for group

testing in 1997

Experiment 3: AL Coastal Plain

Spray date 1 Spray date 2

Product Top whorl Terminal Top whorl Terminal

Orthene 0.7 aa 4.1 a 1.0 a 0.0 a

Pounce 3.2 ab 13.7 a 4.7 a b 6.8 a

Mimic 4.2 ab 6.2 a 6.3 a b 2.0 a

Foray 7.3 b 32.5 b 10.0 b c 9.3 a

Tame 7.5 b 6.6 a 14.7 c 17.5 b

Check 26.3 c 51.1 c 32.5 d 36.7 c

a Means in columns with different letters are significantly different at alpha = 0.05.

m TERMINAL SHOOT

D TOP WHORL

* zero infestation

WARRIOR CONTROL

POUNCE

TREATMENT

Figure I-Mean percent infested shoots for Warrior and Pounce

treated pines on a Georgia upper Coastal Plain site in summer of

1997.

7 0

6 0

- r

FALL LINE REGION, GA

GENERATION 4,1997

m TERMINAL SHOOT

0 TOP WHORL

I c

WARRIOR CONTROL

POUNCE

TREATMENT

Figure 2-Mean percent infested shoots for Warrior and Pounce

treated pines on a Georgia upper Coastal Plain site in late summer

of 1997.

ia
Experiment 4 (1998):

The site in the Georgia Piedmont near Lexington

experienced moderate to heavy tip moth infestation in 1998

with the untreated control plots having near 50 percent

infestation in the top whorl shoots (fig. 3). Both rates of

Imidan8 provided excellent control, being significantly better

than both Pounce@ and untreated control plots

(H=l5.9,P=O.O01, n=5, df=3;). The low dosage rate of

Imidan8 in this trial was very efficacious, and the results

warrant additional testing of this product at lower rates.

CONCLUSIONS

There are several chemical control options in a variety of

chemical classes for reducing damage by NPTM. Simple but

adequate timing models are available for most commercial

pine growing regions and can probably be extrapolated to

areas not specifically covered by recent and current

research. Resistance management should be easily

accomplished by timing sprays and rotating chemicals when

necessary. Forestry benefits greatly from agricultural testing

B

::

g 60-

m Terminal

0 Top Whorl

8

* = zero infe5tation

?I3

s

-__----------------------

C

g 4O2

B --_---__---_-------------

20 -

-__----- --------- ---

* l .

0,

lmidan 0.5 lmlden 1.0 POWlC8

Treatment

---- c&

~5

---- 25

I I rFigure 3-Mean percent infested shoots for two rates of lmidan and

one of Pounce treated pines on a Georgia Piedmont site in summer

of 1998.

of new products. Target specificity and toxicological data are

generally available 5-10 years before a new product is

considered for forestry use. Given this, we do not foresee a

lack of products in the near future for inclusion in a NPTM

management program. The real challenge lies in assessing

the need to spray, and maximizing application efficacy once

the decision is made to use an insecticide.

ACKNOWLEDGEMENTS

We would like to thank International Paper Company

personnel, in particular Scott Cameron and Jimmy

Seckinger, for their invaluable assistance in locating sites for

spray testing.

REFERENCES

Berisford, C. W.; Garguillo, P. M.; Canalos, C. G. 1984. Optimum

timing for insecticidal control of the Nantucket pine tip moth

(Lepidoptera:Tortricidae). Journal of Economic Entomology.

77(1):174-177.

Clarke, S. R.; DeBarr, G. L.; Berisford, C. W. 1990. Life history of

Oracella acufa (Homoptera:Pseudococcidae) in loblolly pine

seed orchards in Georgia. Environmental Entomology. 19( 1):

99-103.

DeBarr, G. L.; Barber, L. R.; McClure, M. S.; Nord, J. C. 1982. An

assessment of the problem of scale and mealybug outbreaks

associated with the use of insecticides in southern pine seed

orchards. Unpublished report on file at the USDA Forest Service,

Forestry Sciences Lab, Athens, GA.

Fettig, C. J.; Berisford, C. W.; Dalusky, M. J. 1999. Revision of a

timing model for chemical control of the Nantucket pine tip moth

(Lepidoptera:Tortricidae) in the southeastern coastal plain.

Journal of Entomological Science. 33(4): 336-342.

Fe&g, C. J.; Berisford, C. W. 1999. A comparison of three common

indices used for estimating Nantucket pine tip moth damage in

the field. Journal of Entomological Science. 34(2): 203-209.

Garguillo, P. M.; Berisford, C. W.; Godbee, J. F., Jr. 1985. Prediction

of optimal timing for chemical control of the Nantucket pine tip

moth, Rhyacionia frusfrana (Comstock)(Lepidoptera:Tortricidae),

in the southeastern coastal plain. Journal of Economic Entomology.78:148-154.

McCravy, K. W.; Dalusky, M. J.; Berisford, C. W. 2001. Effects of

broad spectrum and biorational insecticides on parasitoids of the

Nantucket pine tip moth (Lepidoptera:Tortricidae). Journal of

Economic Entomology. 94(l): 112-115.

1 9
MAXIMIZING PINE TIP MOTH CONTROL: TIMING IS EVERYTHING

Christopher J. Fettig’

INTRODUCTION

The impact of the Nantucket pine tip moth, Rbyacionia

frustrana (Cornstock), has become of increasing concern as

standard silvicuitural practices have intensified in southern

pine production. The associated silvicultural manipulations of

site preparation, herbaceous weed control, release, bedding

and fertilization have shortened rotation lengths and

increased volume yields (Nowak and Berisford 2000) but

have often elevated tip moth infestation levels (Nowak and

Berisford 2000, Ross and others 1990). As a result,

insecticide applications are now being considered as part of

silvicultural prescriptions for intensively-managed pine

plantations.

There are several insecticides registered for controlling tip

moth infestations in forest plantations. The difficulty is that

the availability of these compounds tends to fluctuate as

older materials lose their registration (i.e., some

organophosphates) and new compounds expand their labels

to include forest plantations (i.e., spinosad). Therefore, a

complete listing of registered insecticides is not provided

here, but can easily be located in a current pest control

handbook distributed by State Cooperative Extension

offices.

Direct control with contact insecticides is effective if properly

timed to target susceptible life stages of the pest. Timing is

critical due to the non-systemic, relatively short residual

nature of most insecticides currently registered for tip moth

control. Spraying insecticides at about 30-80 percent egg

hatch maximizes control, and corresponds with an

abundance of first and second instar larvae exposed on

infested shoots (Berisford and others 1984, Gargiullo and

others 1985, Kudon and others 1988). These stages are

most susceptible to control due to their small size, presence

on the tree surface, and movement over sprayed areas when

searching for new feeding sites. Insecticide applications

should therefore target these life stages to maximize

efficacy.

Several spray timing models are available to meet these

objectives (table I), and there continues to be a gradual

evolution in the development of models for specific

compounds and locations. Berisford and others (1984) first

identified the need for spray timing as a way of reducing

application frequencies in Georgia Christmas tree

plantations. The first biological timing schedules were

developed for dimethoate (CygonB) and esfenvalerate

(PydrinB) insecticides using degree-day accumulations to

predict optimum spray dates in the Georgia Piedmont

(Gargiullo and others 1983) and Coastal Plain (Gargiullo

and others 1985). In general, the procedure involves

accumulating degree-day summations commencing on the

date of first catch in pheromone-baited traps for each

generation, and continuing until an experimentally

determined sum is attained. This sum indicates the optimal

spray date for each generation and is based on moth

phenology. Most published models are based on variations

of this theme with spray prediction values being derived from

moth phenology distributions or insecticide spray timing

trials (table 1).

Although largely effective, improper use of spray timing

models has occasionally led to errors in spray date

predictions. These models require a detailed knowledge of

tip moth biology, proper pheromone trap deployment,

intensive trap monitoring, knowledge of degree-day

calculations, conversions and utility, and the ability to

acquire daily maximum and minimum temperatures on or

near the site. Scheduling problems may still arise from shortterm advance notice of approaching spray dates or

inclement weather patterns that limit insecticide spray

opportunities. The development of an efficient method that

permits prediction of spray dates in the absence of spray

timing models is highly desirable.

PREDICTIONS OF OPTIMAL SPRAY DATES FROM

LONG-TERM WEATHER RECORDS

Procedures

Mean maximum and minimum temperatures for each day of

the year were obtained for selected weather stations in

Virginia (n = 49) North Carolina (n = 58) South Carolina (n

= 45) Georgia (n = 70) Alabama (n = 54) Mississippi (n =

52) and northern Florida (n = 26). Daily mean maximum and

minimum temperatures for each weather station were placed

in a spreadsheet program (Microsoft Excel, Microsoft Corp.,

Seattle, WA), and then transferred to a degree-day

computational program (Degree-Day Utility, University of

California Statewide Integrated Pest Management Program,

Davis, CA). Degree-days were accumulated using the singlesine, intermediate cutoff computation method (Seaver and

others 1990) with lower and upper developmental thresholds

of 9.5 and 33.5 “C, respectively (Haugen and Stephen

1984). The annual number of degree-days accumulated at

each station was divided by 754 degree-days “C (the

minimum required for completion of a single generation) and

rounded to the next lowest whole number to provide an

estimate of the number of tip moth generations occurring

annually at that location (Ross and others 1989). The

weather station locations and the numbers of corresponding

generations were then mapped for each state.

1 Postdoctoral Research Associate, 413 Biological Sciences Building, Department of Entomology, The University of Georgia, Athens, GA 30602.

Citafion for proceedings: Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.

2 0
Table l-Papers published on the timing of insecticide applications for controlling tip moth infestations

Authors Title General description

Gargiullo and

others 1983

Berisford and

others 1984

Gargiullo and

others 1984

Gargiullo and

others 1985

Kudon and

others 1988

Malinoski and

Paine 1988

Pickering and

others 1989

Richmond

1992

Fettig and

others 1998

Fettig and

Berisford 1999

Fettig and

others 2000a

Fettig and

others 2000b

Nowak and

others 2000

How to time dimethoate sprays against the

Nantucket pine tip moth

Optimum timing for insecticidal control of the

Nantucket pine tip moth

Mathematical description of Rhyacionia

frustrana (Lepidoptera: Tortricidae) cumulative

catches in pheromone traps, cumulative eggs

hatching, and their use in timing of chemical

control

Prediction of optimal timing for chemical

control of the Nantucket pine tip moth in the

southeastern coastal plain

Refinement of a spray timing technique for the

Nantucket pine tip moth (Lepidoptera:

Tortricidae)

A degree-day model to predict Nantucket pine

tip moth flight in southern California

An automated system for timing insecticidal

sprays for Nantucket pine tip moth control

Timing sprays by a heat unit model of spring

flight of the Nantucket pine tip moth in North

Carolina

Revision of a timing model for chemical control

of the Nantucket pine tip moth (Lepidoptera:

Tortricidae) in the southeastern coastal plain

Nantucket pine tip moth phenology in eastern

North Carolina and Virginia: implications for

effective timing of insecticide applications

Nantucket pine tip moth (Lepidoptera:

Tortricidae) phenology and timing of

insecticide applications in seven southeastern

states

Effects of Nantucket pine tip moth insecticide

spray schedules on loblolly pine seedlings

Efficacy tests and determination of optimal

timing values to control Nantucket pine tip

moth (Lepidoptera: Tortricidae) infestations

Spray timing model using pheromone-trap data

and degree-day summations for a 3 generation

phenology in the Georgia Piedmont

Non-systemic chemical control must be directed

toward early developmental stages

Spray timing model for a 3 generation

phenology in the Georgia Piedmont and

validated and refined in Oklahoma and North

Carolina

Spray timing model using pheromone-trap data

and degree-day summations for a 4 generation

phenology in the Georgia Coastal Plain

Two insecticide applications were necessary for

adequate control of the third generation in the

Georgia Piedmont

Prediction of optimum spray dates using trap

catch data and a degree-day flight model for

control of a 4 generation phenology in California

Automated computer system that provided daily

predictions of optimal spray dates for 70

stations in Georgia (obsolete)

A spray timing model developed for North

Carolina

Corrected spray timing values are reported for

data initially provided by Gargiullo and others

1985

Spray timing model using trap catch data and

degree-day summations for a 3 generation

phenology in eastern North Carolina and

Virginia

Optimal spray periods are provided for locations

(354) with either 3 or 4 generation phenologies

in the southeastern U.S.A. Allows for

surprisingly accurate timing without using spray

timing models

A n optimal insecticide spray schedule is

identified that eliminates four sprays over a two

year period when compared to standard

applications

Optimal spray timing values are provide for

permethrin, lambda-cyhalothrin, spinosad, and

Bacillus thuringiensis Berliner in the Georgia

Piedmont

2 1
The length of winter diapause and the precise conditions

required to break it are unknown for the Nantucket pine tip

moth, and temperatures above the lower developmental

threshold may occur throughout the year. Therefore, spray

timing prediction values were accumulated from an

arbitrarily established biofix of 7 January where four

generations occur annually and 1 March where three

generations occur annually. These dates are based on the

time of average male moth emergence for the first

generation. Three different sets of spray timing values were

used to predict optimal spray dates. In portions of Virginia

and North Carolina where three generations occur annually

the values were 188, 784, and 1472 degree-days “C (Fettig

and Berisford 1999). In remaining portions of the Southeast

where three generations occur annually the values were

204, 968, and 1787 degree-days “C (Fettig and Berisford

1999). In locations where four generations occur annually

the values were 237, 899,1757, and 2513 degree-days “C

(Fettig and others 1998). Spray timing values are not

available for controlling populations with two or five annual

generations and therefore are not provided for such

locations. Degree-days were accumulated continuously for

each weather station from the assigned biofix until the

appropriate spray prediction value was reached for each

generation. The corresponding date was designated the

optimal spray date. Each optimal spray date was then

located in an optimal spray period established by dividing

the calendar year into 5day increments.

To test the validity of spray period predictions, the

predictions were compared to 44 spray dates determined at

16 different field sites during 1996-1998. The fielddetermined spray dates were calculated on site by

monitoring moth flight with pheromone-baited sticky traps

(Pherecon 1 C; Trece Inc., Salinas, CA) and accumulating

degree-day totals using continuously recording

biophenometers (Model TA51; Dataloggers Inc., Logan, UT).

During this period, mean temperatures were generally

normal (1996) below normal (1997) and above normal

(1998) (Athens, GA June departure from normal: -0.06 “C, -

2.33 “C, and 2.06 “C, respectively) throughout most of the

Southeastern U.S.A.

Results and Discussion

Our phenology predictions indicated the moth would

complete two to five generations annually in this region. Two

generations occurred throughout the Mountain Province in

Virginia and North Carolina and at some of the highest

elevations of South Carolina and Georgia. Three generations

occurred throughout the Piedmont Plateau and in the

Coastal Plain of Virginia and parts of North Carolina. Four

generations occurred in much of the remaining portions of

the Coastal Plain to a northern limit apparently located in

Craven County, North Carolina. Five generations were

predicted for extreme southern portions of Alabama,

Georgia and Mississippi, and in northern Florida.

Table 2 provides a brief example of how the optimal spray

periods predictions are to be utilized. For example, if you

wish to control tip moth in a pine plantation in the vicinity of

Athens, GA with a pyrethroid insecticide, you would initially

find the nearest weather station located to your vicinity on

the maps provided in the original publication (see Fettig and

others 2000a). After finding this location as site 7, you would

look up site 7 on table 2. The optimal spray periods for this

site are predicted for 16-20 April, 20-24 June, and 4-8

Table 2-Site number, location, and optimal spray period predictions for 15 weather stations located

throughout Georgia

No. Location 1

Spray period

2 3 4

1 Albany

2 Alma

3 Alpharetta

4 Americus

5 Appling

6 Ashburn

7 Athens

8 Atlanta

9 Augusta

1 0 Bainbridge

1 1 Blairsville

1 2 Brunswick

1 3 Byron

1 4 Calhoun

1 5 Camilla

March 17-21

-a

April 21-25

March 22-26

April 11-15

March 27-31

April 16-20

April 16-20

April 1-5

March 12-l 6

-

May 21-25

-

June 30-July 4

May 26-30

June 20-24

May 26-30

June 20-24

June 15-19

May 31-June 4

May 21-25

-

- -

April 1-5 June 5-9

April 16-20 June 25-29

- -

July IO-14

-

Aug 24-28

July 15-19

Aug 9-13

July 15-19

Aug 4-8

Aug 4-8

July 20-24

July IO-14

-

-

July 25-29

Aug 14-18

-

Aug 19-23

-

Aug 29 Sept 2

Aug 29 -Sept 2

Sept 3-7

Aug 19-23

-

-

Sept 8-l 2

-

a 11-11 refers to spray periods that are not applicable to spray timing because models have not been developed for

populations with 2 or 5 annual generations.

2 2
August, and therefore treatments should be applied during

these intervals. The lack of data in the column labeled spray

period four indicates only three annual generations occur at

this location.

Fourteen (31.8 percent) of the predicted spray periods

agreed with field-determined spray dates, 21 (47.7 percent)

differed by one spray period (i.e., a five day arbitrarily

established interval), six (13.6 percent) differed by two spray

periods, and three (6.8 percent) differed by three spray

periods. Six (66.7 percent) of the spray predictions that

differed by two or three periods occurred during the first tip

moth generation and may reflect discrepancies between the

arbitrary biofix date and the actual initiation of moth flight at

these locations.

Spray timing values are typically determined experimentally

by applying insecticide sprays at specified degree-day

intervals, assessing damage levels for each spray, and using

second degree polynomial regressions (parabolas) to

determine optimal spray timing values. Although an optimal

value exists, approximately 125 degree-days surround the

optimal value in which little or no variation in damage levels

is observed (from Gargiullo and others 1985). Assuming a

typical mean daily temperature of 15.5 “C for the first

generation, 20.5 calendar days of thermal units would occur

during the 125 degree-day interval. In all cases, our

predictions will meet this criterion. However, it also shows

why spray timing becomes more critical in later generations.

Assuming a mean daily temperature of 26.7 “C, the same

125 degree-day interval represents only 7.3 days of thermal

units. Under these circumstances, our predictions would be

effective 87 percent of the time.

EFFECTS OF INSECTICIDE SPRAY SCHEDULES

ON LOBLOLLY PINE SEEDLING YIELDS

We are currently able to time insecticide applications

accurately within a generation using either spray timing

models or the optimal spray periods that were discussed

above. However, it may not be necessary to treat each and

every tip moth generation for the first two or three years

following stand establishment as is the common convention.

The objective of this study was to develop a tip moth control

program that maximizes yield in loblolly pine, Pinus faeda L.,

with the minimum number of insecticide applications during

the first two years following stand establishment (Fettig and

others 2000b).

Procedures

In 1997, two newly-planted (1 -yr old) and two Z-yr old

plantations were selected as study sites in the Georgia

Piedmont. Three randomized complete blocks were

established in each plantation. Each block consisted of eight

randomly assigned plots corresponding with the number of

treatments and contained 12 randomly selected trees (N =

1152). In 1998, three additional I-yr old and four additional

2-yr old plantations were selected as study sites in the

Georgia Piedmont and North Carolina and Virginia Coastal

Plain. Five randomized complete blocks were established in

each plantation. Each block contained eight plots and eight

randomly selected trees within a plot (N = 2560). All sites

had received herbaceous weed control and were planted

with 1-O loblolly pine seedlings. It was previously confirmed

that three tip moth generations occurred in each region.

The timing of insecticide applications was determined by

monitoring male moth emergence for each generation with

sex pheromone lures in Pherocon 1 C sticky traps (Trece

Inc., Salinas, CA), and accumulating degree-days after the

detection of an average of one moth per trap per day using

continuously recording biophenometers (Omnidata T151;

Dataloggers Inc., Logan, UT). Insecticides were applied at

188,261 and 315 degree-days “C in North Carolina and

Virginia, and 204, 308 and 293 degree-days “C in Georgia

for each of the three tip moth generations (Fettig and

Berisford 1999).

Applications included timed sprays of permethrin (Pounce

3.2 EC) with hand-pump backpack sprayers (Model 425;

Solo”, Newport News, VA) at a rate of 0.6 ml of formulated

product per liter of water. Treatments consisted of all

possible combinations of insecticide spray schedules based

on three annual tip moth generations, specifically: C)

untreated control, 1) first generation, 2) second generation,

3) third generation, l&2) first and second generation, l&3)

first and third generation, 2&3) second and third generation

and A) all generations. Applications were made during the

first year only at three sites, second year only at six sites,

and both the first and second year following stand

establishment at two sites.

Damage estimates were taken on 30 randomly selected

trees in Treatments C (untreated control) and A (all

generations) for each site during the pupal stage of each

generation. The total number of shoots (i.e., > 10 linear cm

of apical stem containing foliage) and number of infested

shoots were recorded in the terminal plus top whorl of each

tree to assess insecticide efficacy. Growth statistics were

taken in November 1997 and 1998 on each tree. Basal

diameter (D) was measured with a caliper at 2.5 cm above

ground surface. Height (H) was measured from the root

collar to the tip of the terminal leader using a cm graduated

height stick. These values were later used to compute a

volume index (D2H) for each treatment. The growth data

were analyzed as a randomized complete block design and

compared with the Tukey test for separation of treatment

means (Sokal and Rohlf 1995).

Results and Discussion

Insecticide efficacy in both 1 and 2-yr old stands decreased

throughout the year from 90.4 percent control in the first

generation to 77.6 percent and 55.5 percent control in the

second and third generations. Decreasing spray efficacy is

commonly observed as the year progresses due to

increasing asynchrony among susceptible life stages in later

generations (Fettig and others 1998). Control of the first tip

moth generation when insecticide efficacy is highest is also

of particular importance in resistance management by

limiting the proportion of insects that escape sub-lethal

exposures.

Few significant differences were observed among treatment

means when insecticides were applied to age 1 trees.

Treatment A had significantly larger volume estimates than

the untreated control. No other significant differences were

2 3
observed among the remaining treatment means. This

suggests that spraying tip moth infestations only during the

first year following stand establishment is ineffective unless

every generation is included in the control schedule. We

observed a 63.1 percent increase in volume index by

applying Treatment A.

More significant differences were observed among treatment

means when insecticides were applied to age 2 trees.

Treatment l&3 (generations 1 and 3) Treatment 2&3

(generations 2 and 3) and Treatment A had significantly

larger diameter, height and volume estimates than the

untreated control. No significant differences were observed

among Treatments l&3,2&3 and A. At least two insecticide

sprays were required to produce a significant difference in

all three growth measurements. An optimal insecticide spray

schedule for controlling tip moth infestations in age 2 trees

with insecticide applications applied during the second year

includes either spraying the first and third or second and

third generations thereby eliminating one spray without any

significant effect on volume yield. We observed a 39.0

percent increase in volume by applying Treatment l&3, and

a 38.9 percent increase in volume by applying Treatment

28~3.

Significant differences were observed among treatment

means when insecticides were applied to the same trees at

both age 1 and age 2. Treatment 1 (first generation only) had

a significantly larger volume index than several other

treatments including the control. We observed a 74.5

percent increase in volume index by applying Treatment 1

during the first two years following stand establishment. This

is the largest increase in volume index observed relative in

this study.

The application of timed permethrin sprays during the first

generation of both the first and second year following stand

establishment appears to be the optimal insecticide spray

schedule. Insecticide efficacy is greatest during the first

generation, and coincides with the time when recurrent

growth species such as loblolly pine typically have their

largest growth flush of the year (Oliver and Larson 1996).

Recently, it has been confirmed that control of the first

generation has an extended benefit (Coody and others

2000). This suggests that previous tip moth attacks

predispose trees to heavier attacks during subsequent

generations, possibly due to bud proliferation from previous

attacks, changes in host physiology, or simply that females

emerging from infested trees mate and deposit eggs on the

same trees. Control of the first generation may also be

important in reducing recruitment from adjacent stands by

reducing the number of suitable oviposition sites (i.e., bud

proliferation resulting from tip moth attacks) and the number

or density of calling females.

Currently, most tip moth control programs target at least the

first and second year following planting and insecticides are

repeatedly applied to control each generation. Our data

suggest that it is unnecessary to control each generation to

significantly increase volume yields. The optimal insecticide

spray schedule program for a three generation tip moth

phenology would include a single first generation spray

during the first two years following planting. This would

reduce the current practice by four sprays over the two year

period, which would be both economically and ecologically

beneficial, two important criteria for an integrated pest

management program.

CONCLUSIONS

The application of insecticides to manage tip moth

infestations is likely to become more common in the future

as we attempt to increase fiber production. Spray timing is

critical to successfully controlling these infestations. The

questions remains as to what degree of accuracy is

acceptable, and how inexpensively it can be obtained.

REFERENCES

Berisford, C. W.; Gargiullo P. M.; Canalos, C. G. 1984. Optimum

timing for insecticidal control of the Nantucket pine tip moth

(Lepidoptera: Tortricidae). Journal of Economic Entomology 77:

174-177.

Coody, A. R.; Fettig, C. J.; Nowak, J. T.; Berisford, C. W. 2000.

Previous tip moth infestation predisposes trees to heavier

attacks in subsequent generations. Journal of Entomological

Science. 35: 83-85.

Fettig, C. J.; Berisford, C. W.; Dalusky, M. J. 1998. Revision of a

timing model for chemical control of the Nantucket pine tip moth

(Lepidopetra: Tortricidae) in the southeastern coastal plain.

Journal of Entomological Science 33: 338-342.

Fettig, C. J.; Berisford, C. W. 1999. Nantucket pine tip moth

phenology in eastern North Carolina and Virginia: implications

for effective timing of insecticide applications. Southern Journal

of Applied Forestry 23: 30-38.

Fettig, C. J.; Dalusky, M. J.; Berisford, C. W. 2000a. Nantucket pine

tip moth (Lepidoptera: Tortricidae) phenology and timing of

insecticide applications in seven southeastern states. Res. Pap.

SRS-18. Asheville, NC: U.S. Department of Agriculture, Forest

Service, Southern Research Station. 21 p.

Fettig, C. J.; McCravy, K. M.; Berisford, C. W. 2000b. Effects of

Nantucket pine tip moth insecticide spray schedules on loblolly

pine seedlings. Southern Journal of Applied Forestry 24:

106-111.

Gargiullo, P. M.; Berisford, C. W.; Canalos, C. G.; Richmond, J. A.

1983. How to time dimethoate sprays against the Nantucket pine

tip moth. Georgia Forestry Commission Forest Research Paper

No. 44. Macon, Georgia: Georgia Forestry Commission. 11 p.

Gargiullo, P. M.; Berisford, C. W.; Godbee, J. F., Jr. 1985. Prediction

of optimal timing for chemical control of the Nantucket pine tip

moth, Rbyacionia frustrana (Comstock) (Lepidoptera:

Tortricidae), in the southeastern coastal plain. Journal of

Economic Entomology 78: 148-154.

Haugen, D. A.; Stephen, F. M. 1984. Development rates of Nantucket

pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera:

Tortricidae) life stages in relation to temperature. Environmental

Entomology 13: 56-60.

Kudon, L. H.; Berisford, C. W.; Dalusky, M. J. 1988. Refinement of a

spray timing technique for the Nantucket pine tip moth (Lepidoptera: Tortricidae). Journal of Entomological Science 23:

180-186.

24
Malinoski, M. K.; Paine, T. D. 1988. A degree-day model to predict

Nantucket pine tip moth, Rhyacionia frusfrana (Comstock)

(Lepidoptera: Tortricidae) flights in southern California. Environmental Entomology 17: 75-79.

McCravy, K. W.; Berisford, C. W. 1998. Parasitism by Trichogramma

spp. (Hymenoptera: Trichogrammatidae) in relation to Nantucket

pine tip moth (Lepidoptera: Tortricidae) egg density and location.

Environmental Entomology 27: 355-359.

Nowak, J. T.; Berisford, C. W. 2000. Effects of intensive forest

management practices on insect infestation levels and loblolly

pine growth. Journal of Economic Entomology 93: 336-341.

Nowak, J. T.; Fettig, C. J.; McCravy, K. W.; Be&ford, C. W. 2000.

Efficacy tests and determination of optimal spray timing values

to control Nantucket pine tip moth (Lepidoptera: Tortricidae)

infestations. Journal of Economic Entomology 93: 1708-I 713.

Oliver, C. D.; Larson, B. C. 1996. Forest stand dynamics. John Wiley

and Sons, Incorporate, New York. 520 p.

Pickering, J.; Ross, D. W.; Berisford, C. W. 1989. An automated

system for timing insecticidal sprays for Nantucket pine tip moth

control. Southern Journal of Applied Forestry 13: 184-l 87.

Richmond, J. A. 1992. Timing sprays by a heat unit model of spring

flight of the Nantucket pine tip moth in North Carolina. Res. Note.

Asheville, NC: U. S. Forest Service Southeast Forest Experiment

Station. 4 p.

Ross, D. W.; Pickering, J.; Berg, J. D.; Berisford, C. W. 1989.

Mapping Nantucket pine tip moth (Lepidoptera: Tortricidae)

phenology in Georgia. Journal of Entomological Science 24:

405-412.

Ross, D. W., Be&ford, C. W.; Godbee, J. F., Jr. 1990. Pine tip moth,

Rhyacionia spp., response to herbaceous vegetation control in

an intensively site-prepared loblolly pine plantation. Forest

Science 36: 1105-1118.

Seaver, D.; Strand, J.; Strawn, A. J. 1990. Degree day utility user’s

guide. Version 2. Davis, California: University of California. 86 p.

Sokal, R. R.; Rohlf, F. J. 1995. Biometry, 3rd edition. W. H. Freeman

and Company, New York. 887 p.

2 5
enneth

b&act-Effects of herbicide and insecticide applications on parasitism of the Nantucket pine tip moth, Rhyacionia

frusfrana (Comstock) were examined in 2-yr-old loblolly pine (Pinus taeda L.) plantations in Georgia. Total parasitism rates

varied significantly among tip moth generations, but there were no differences in parasitism rates between herbicide-treated

and untreated plots. Significant differences in the relative abundance of parasitoid species were found among generations,

with Euryfoma pini Bugbee being the most common in summer and Lixophaga mediocris Aldrich the most abundant in

spring. Plots treated with the insecticide, Orthene, had significantly less parasitism than plots treated with tebufenozide,

BaciNus fburingiensis var. kursfaki, or untreated check plots. Effects of acephate treatments were species-specific, with no

apparent effects on parasitism by L. mediocris Aldrich but significantly decreased parasitism by Ha/fiche//a rhyacioniae

Gahan.

INTR

Damage caused by the Nantucket pine tip moth, Rhyacionia

frusfrana (Cornstock) is highly variable, and may be

negligible or high enough to cause tree mortality. Large

population fluctuations have been associated with common

southern forest regeneration practices, which often include

intensive site preparation, chemical control of competing

vegetation, and fertilization to increase seedling growth

(Miller and Stephen 1983, Nowak and Berisford 2000). The

Nantucket pine tip moth has a high reproductive potential,

which may be constrained to some degree by high

parasitism rates (Eikenbary and Fox 1968a,b; Freeman and

Berisford 1979; Wallis and others 1980; Gargiullo and

Berisford 1983; Warren 1985; McCravy and Berisford 2000).

Potential effects of forest management practices on tip moth

parasitoids have received little attention. It has been

suggested that natural enemies of herbivorous insects are

more effective in diverse systems than in simple ones

(Pimentel 1961). In a review of tests of this natural enemy

hypothesis, however, Russell (1989) found the results to be

inconclusive for parasitism.

insecticidal control of tip moths may be necessary in

intensively-managed commercial pine plantations. A number

of “hard” pesticides such as acephate, an organophosphate,

have been used successfully to control tip moth populations.

However, organophosphates often cause high mortality

among natural populations of parasitoids and predators as

well (Croft 1990). Alternative insecticides, such as Bacillus

fhuringiensis var. kursfaki (Btk) and the insect growth

regulator, tebufenozide, may be more compatible with tip

moth natural enemies, In this paper we describe two studies

investigating effects of herbicidal vegetation control and

conventional and biorational insecticidal treatments on tip

moth parasitism.

--

ew ontr

This study was conducted in 1996-97 in three 2-yr-old

loblolty pine plantations in the Georgia coastal plain. The

plantations ranged from 44 to 70 ha. Two sites were located

in Burke County, near Waynesboro, and one in Bulloch

County, near Statesboro. Each site was mechanically

prepared, and 1-O bareroot improved loblolly pines were

machine planted at densities of approximately 1492 trees

per ha in the winter of 1994-95. In spring, 1996, each tract

was divided approximately in half, with one randomly

selected half receiving a herbicidal treatment of hexazinone

and sulfometuron methyl at rates of 2.34 and 0.22 liters/ha,

respectively. The remaining halves were left untreated. The

Waynesboro sites were treated again in the fall, 1996 with

imazapyr and glyphosate at 0.58 and 2.38 liters/ha,

respectively. Herbicides were applied by helicopter at the

Waynesboro sites and by tractor at the Statesboro site. In

spring, 1996, 50 pines were randomly chosen in each

treatment of each study site to serve as permanent study

trees. Tip moth infestations were evaluated by counting

numbers of infested shoots on the permanent study trees in

each generation, when tip moths were in the late larval and

pupal stages and damage was most obvious. Non-pine

vegetation was quantified and characterized for each

treatment plot as well. Twenty randomly located 1 m*

quadrats were established in each plot at each site during

each tip moth generation. For each quadrat, a visual

estimate of percentage ground cover was taken, the

maximum height of vegetation was measured, and presence

or absence of flowering vegetation was recorded.

Specimens of each plant species present were taken,

returned to the laboratory, and identified to species. The

spring, 1997 (1 st)generation of the Statesboro site was not

included in the study because of low tip moth populations.

1 McCravy, Assistant Professor, Department of Biological Sciences, Western Illinois University, Macomb, IL 61455; Daiusky, Research Coordinator, and Berisford, Professor, Department of Entomology, University of Georgia, Athens, GA 30602.

Citation for proceedings: Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.

26
Collections of infested shoots for rearing of tip moths and

parasitoids also were made during the late larval/pupal

stages of each tip moth generation. In each treatment plot,

2,000 infested shoots were randomly collected from nonpermanent study trees. Summer (2nd generation) 1996

collections were made on 26-27 June and 2-3 July at the

Statesboro and Waynesboro sites, respectively. Late

summer (3rd generation) 1996 shoots were collected on 7-8

August and IO-II August, respectively. Collections of

shoots for the overwintering (4th) generation were made in

two stages. Half of the shoots were collected on 22

September and 26 September, 1996 at the Statesboro and

Waynesboro sites, respectively, and half were collected on

16 January and 21 January, 1997. This was done in order to

sample parasitoids that might emerge before the onset of tip

moth pupal diapause as well as those emerging in late

winter and early spring. Spring (1st generation) 1997

collections were made on 3-4 May at the Waynesboro sites.

Because of low tip moth infestations for this generation,

1,000 shoots were collected from each treatment plot.

Shoots were returned to the laboratory and placed in

ventilated rearing containers (Berisford and others 1971)

separated by site and treatment. Emerging adult moths and

parasitoids were collected every 2-3 days. Moths were

counted and parasitoids were counted and identified to

species, if possible, using Yates’ (1967) key, and placed in 70

percent EtOH. At the end of emergence for each collection,

shoots were removed from the rearing cans, dissected, and

examined for the presence of tip moths, parasitoids, or

cocoons. Series of each apparent species were sent to

appropriate taxonomic authorities for positive

determinations. Tip moth parasitism rates were determined

based on relative numbers of emerged parasitoids and

moths. Two parasitoids, Hyssopus rhyacioniae Gahan and

Pferomalus sp. Swederus, were determined to be gregarious

based on dissection of individual tip moth-infested shoots,

and averaged 12.2 + 1.20 (mean + SEM, n = 15) and 2.92 +

0.45 (n = 12) individuals per brood, respectively. Total

numbers of individuals reared for these two species were

divided by these means to get a more realistic estimate of

the number of parasitism events.

Parasitoids were also collected using malaise traps in order

to get an estimate of the relative abundances of parasitoids

in the herbicide-treated and untreated plots. Two traps, one

in each treatment plot, were operated at the Waynesboro 1

and Statesboro sites for eight five-day trapping periods from

mid-June to early October 1996. Traps were randomly

relocated for each trapping period. Insects were collected in

70 percent EtOH. At the end of each trapping period,

samples were taken to the laboratory and parasitoids,

defined as Parasitica (Huber 1993) plus tachinids (Diptera),

were removed and counted. Recognizable tip moth

parasitoids were also separated and counted.

Numbers of infested shoots and parasitism rates were each

compared between treatments and among generations and

sites using 3-way analysis of variance, with Tukey’s multiple

comparisons test. Relative variation in infestation levels and

parasitism rates for each treatment, pooled across site and

generation, was measured using the coefficient of variation

(Sokal and Rohlf 1995). Comparison of proportions of t-f.

rhyacioniae reared from tip moth-infested shoots collected

from herbicide-treated vs. untreated plots was made using

paired t-tests. Numbers of parasitoids captured in malaise

traps were compared between treatments and sites using 2-

way analysis of variance. All analyses were performed using

the SigmaStat Version 2.0 software package (Jandel

Scientific Software 1995).

Insecticide Study

This study was conducted in a 2-yr-old loblolly pine

plantation, of approx. 80 ha, in Taylor Co., GA. Pines ranged

from 0.6 m to 1.2 m in height. Tip moth populations were

high, with a shoot infestation rate of approx. 66 percent in

the top whorl of branches for the 1st generation. Sprays

were timed for optimum efficacy with a degree-day timing

model developed using an organophosphate insecticide

(dimethoate) for the Nantucket pine tip moth (Garguillo and

others 1985). Moth flight was monitored with four wing traps

(Pherocon 1 C@ baited with Nantucket pine tip moth lures

(Trece Inc., Salinas, CA). Upon initiation of the summer (2nd)

tip moth generation, degree-days were accumulated with a

continuously recording biophenometer.

The study was set up as a randomized complete block

design, with two replicates (blocks) per treatment and

untreated control, for a total of eight plots. Plots were

rectangular and 2.8 ha. Blocks were approximately 30 m

apart, and plots were a minimum of 150 m apart. Acephate

(10.8 percent [Al]), Btk (100 percent [Al]), and tebufenozide

(2.0 percent [Al]) were used as treatments. Acephate and

tebufenozide were applied at a rate of 4.6 liters/ha, while Btk

was applied undiluted at 0.77 liters/ha.

Applications were made by helicopter with a 9.1 m air foil

simplex boom and spray system. Acephate and tebufenozide

were delivered at a rate of 68.9 liters/min. Btk was sprayed

at 11.7 literslmin. Acephate and tebufenozide were applied

on the evening of 3 June 1998. Wind speed was O-5 km/h,

and temperature and relative humidity were 30” C and 66

percent, respectively. Btk was sprayed in the early morning

on 4 June 1998. Wind speed was O-8 km/h, and

temperature and relative humidity were 25” C and 99

percent, respectively. Coverage was monitored by deploying

10 water sensitive cards in each spray plot.

Insecticide efficacy was evaluated on 50 randomly selected

trees in each plot by assessing percentage infestation of

shoots in the top whorl after moths had reached the late

larval/pupal stages, in early July. At that time, approx. 500

damaged shoots were randomly collected from the interior

1.2 ha of each plot for rearing of adult moths and

parasitoids. Most tip moth parasitoids are koinobionts and

emerge from late larvae and pupae of the moths. Shoots

were placed in ventilated rearing containers (Berisford and

others 1971). Emerging adult tip moths and parasitoids were

collected weekly and stored in 80 percent EtOH.

Treatment effects on overall parasitism rates were analyzed

using 2-way analysis of variance with Tukey’s multiple

comparison test. Variation in contribution of individual

parasitoid species to overall parasitism between each

treatment and control was examined using the chi-square

test of independence (Sokal and Rohlf 1995). Speciesspecific differences were evaluated by comparing cell2 7
specific contributions to the overall chi-square to a critical

value of 3.841, using a one-degree-of-freedom criterion at

an alpha value of 0.05 (Freeman 1987). Ail statistical

analyses were done using SigmaStat, version 2.0 (Jandel

Scientific Software 1995).

RESULTS

Vegetation Control Study

The most common plant species found (during sampling

months in which flowering individuals were present) are

shown in Table 1. Total vegetation was greater in untreated

than herbicide treated plots for all three parameters

measured, pooled across site (table 2).

Percent shoot infestation was higher in the untreated plots

(10.517 f. 0.958) than in the treated plots (2.992 + 0.494) (f

= 121.731; df = 1,6; P c 0.001). Percent shoot infestation

among generations ranged from 5.372 + 1.521 for the late

summer generation to 8.703 for the winter generation, and

were marginally nonsignificant (f = 4.681; df = 3‘6; P =

0.052). Infestation rates among sites ranged from 5.924 +

1.545 for the Waynesboro 1 site to 7.605 + 2.121 for the

Waynesboro 2 site, with no significant differences (F =

2.027; df = 2,6; P = 0.213) There were no significant

interaction effects. Relative variation in infestation levels was

much greater in treated than untreated plots (CV = 57.18

percent vs. 32.89 percent, respectively).

Mean tip moth parasitism rates were 51 .O percent + 6.61

percent and 48.2 percent t. 6.17 percent in the herbicidetreated and untreated plots, respectively. Rates were not

significantly different between treatments (f = 1.17; df = 1, 6;

P = 0.321). Parasitism rates were different among sites (F =

22.91; df = 2, 6; P = 0.002) and generations (F = 92.90; df =

3, 6; P < 0.001). Rates were significantly higher at

Statesboro than at the Waynesboro sites. Rates of

parasitism were highest in the spring and summer

generations and lowest in the winter (fig. 1). There were no

significant interaction effects. Relative variation in parasitism

rates was similar in treated and untreated plots (CV = 43.02

percent vs. 42.46 percent, respectively).

Overall, 9,629 parasitoids were reared, representing 4143.5

parasitism events and 19 species in nine families. Three

parasitoids, Lixophaga mediocris Aldrich, Ewytoma pini

Bugbee, and Hyssopus rhyacioniae Gahan accounted for

over 70 percent of total parasitism. Euryfoma pini was the

most abundant species in the summer, but was relatively

rare in winter and spring (fig. 2). Lixophaga mediocris was by

far the most abundant species in the spring. Hyssopus

rhyacioniae accounted for a greater mean proportion of

parasitism in herbicide-treated (19.35 percent) than

untreated (11.58 percent) plots (t = 2.269, df = IO, P =

0.047).

Malaise trapping resulted in 5,550 total parasitoid captures.

Mean numbers of captures per trapping period were 177.19

Table l-Common plant species found in quadrat sampling and month in which flowering

individuals were found

Collection Date

Jun Aw act Apr

Family, Genus, and Species 1996 1996 1996 1997

Asteraceae

Eupatorium capillifolium (Lamarck) Small +

Gnaphalium obtusifolium L. + +

Solidago sp. L. +

Caryophyllaceae

Cerasfium glomeratum Thuillier +

Cyperaceae

Cyperus retrorsus Chapman +

Fabaceae

Stylosanfhes biflora Britton, Sterns, and Poggenburg + +

Tephrosia spicafa (Walter) Torrey and Gray +

Hypericaceae

Hypericum denticulafum Humboldt, Bonpland, and Kunth +

Liliaceae

Smilax sp. L. +

Passifloraceae

Passiflora incarnafa L. +

Polygonaceae

Rumex crispus L. +

Rosaceae

Rubus argutus Link +

Vitaceae

Vitis rotundifolia Michaux +

2 8
9 0

8 0

70

E

2 2 60

.z

e 50

a”

T$ 40

5

al 30

2

20

1 0

0

Table 2-Percent ground cover, maximum height, and frequency of occurrence of

flowering individuals in herbicide-treated and untreated plots for four generations

averaged over two (spring generation) or three (all other generations) study sites

Generation Treatment

Ground

cover

Maximum

height

Frequency of

flowering plants

Percent C m Percent

Summer

Late Summer

Winter

Spring

Totals

Treated

Untreated

Treated

Untreated

Treated

Untreated

Treated

Untreated

Treated

Untreated

21.4 + 2.6 35.2 t. 6.7

51.3 + 10.4 67.5 rt: 16.8

48.5 + 3.3 58.2 2 6.3

71.8 t 0.9 85.1 2 17.8

28.6 + 9.6 60.2 2 12.8

60.7 f 8.8 101.4 t. 13.2

20.4 ; 5.5 23.6 2 12.2

49.8 + a.8 62.9 + 7.9

30.6 _?: 4.4 46.2 + 6.2

59.2 5 4.4 80.7 + 7.4

21.7 5 3.3

40.0 2 18.9

65.0 it 7.6

95.0 2 5.0

16.7 2 12.0

76.7 _t 14.5

30.0 + 5.0

70.0 + 5.0

33.6 + 7.1

70.5 2 a.7

a

b

T

a

T

7 0

6 0

E 5 0

.g

.-

0 40

tii

a

yj 3 0

8

2 0

IO

0

Summer Late Summer Winter

Generation

Spring

Figure I-Mean percent tip moth parasitism (5 SE) for four

generations in the southeastern Georgia coastal plain. Means with

the same letter are not significantly different (P < 0.05, Tukey’s

multiple comparison test).

2 32.08 in the herbicide-treated plots and 169.69 _f 22.67 in

the untreated plots, pooled across site, and did not differ

between treatments or sites (F = 0.0345; df = 1,28; P =

0.854 and F = 0.407; df = 128; P = 0.529, respectively). A

total of 252 known R. frustrana parasitoids were captured.

Mean numbers captured per trapping period were 8.56 +

1.73 in the herbicide-treated plots and 7.19 2 1.20 in the

untreated plots, pooled across site. There were no

differences in captures between treatments (f = 0.403; df =

1,28; P = 0.531) or sites (f = 0.333; df = 1,28; P = 0.568).

Lixophaga mediocris (70 percent of total) and E. phi (14

percent of total) were the most common species captured.

a

i

a

T

a

mE. pini

H. rhyacibniae

- L. mediocris

b

Summer Late Summer Winter

Tip Moth Generation

Spring

Figure 2-Mean percent of total tip moth parasitism (2 SE) due to

three parasitoid species for four generations in the southeastern

Georgia coastal plain. Means with the same letter within a

generation are not significantly different (P < 0.05, Tukey’s multiple

comparison test).

Insecticide Study

Mean percent tip moth infestations in the top whorl of shoots

were48.223.11, 29.5525.59, 33.2528.27, and 34.852

8.27 for the control, acephate, tebufenozide, and Btk plots,

respectively. A total of 465 parasitoids and 723 adult tip

moths were reared, for a parasitism rate of 39.14 percent.

Parasitism rates differed significantly among treatments (F =

19.601: df = 3,3; P = 0.018) (fig. 3). The parasitism rate in the

acephate treated plots was about half that in the check, Btk,

and tebufenozide plots. There were no significant differences

among the check and the latter two treatments.

29
50

4 5

4 0

.gE 3 5

‘ix2 3 0

a” 2 5

: 2 0

$

H ‘5

1 0

5

0 1-

a

a

-.?_--.

Check Btk

a

Tebufenozide Acephate

Treatment

Figure 3-Mean percent tip moth parasitism (2 SE) in three insecticide-treated

R faeda plots and an untreated check plot. Means with the same letter are not

significantly different (P < 0.05, Tukey’s multiple comparison test).

Fourteen species of parasitoids were reared. Of these, E.

pini, an undescribed species of Temelucha Foerster

(Hymenoptera: Ichneumonidae), Ha/fiche//a rhyacioniae

Gahan (Hymenoptera: Chalcididae), and L. mediocris were

the most abundant species, accounting for 89.9 percent of

the total. Relative proportions of parasitism attributable to

these four species differed significantly (X = 22.22; df = 3; P

c 0.001). This difference was primarily due to fewer Ha.

rhyacioniae than expected (X = 3.993; df = 1; P < 0.05) and

more L. mediocris than expected (XL = 8.681; df = 1; P <

0.005) in the acephate treatment plots (fig. 4).

DISCUSSION

Jervis and others (1993) found plants in the families

Umbelliferae and Compositae to be the most frequently

visited by parasitic Hymenoptera. Among the common plants

found in our study, none were Umbellifers, but three

(Eupaforium capikfolium (Lam.) Small, Gnaphalium

obtusifolium L., and Solidago sp. L.) were composites

(Asteraceae, table 1). In a study of flower associations of

Scambus buolianae (Ha&g) (Hymenoptera:

Ichneumonidae), a parasitoid of the European pine shoot

moth, R. buoliana (Schiffermuller), Leius (I 963) found that

E. pini

H. rhyacioniae

L. mediocris

Temelucha sp.

N S

N S

P < 0.0001

Check Btk Tebufenozide Acephate

Treatment

Figure 4-Relative proportions of tip moth parasitism due to four parasitoid species in

three insecticide-treated P. faeda plots and an untreated check plot. NS = not

significant.

30
wasps fed pollen of S. canadensis L. lived significantly

longer than control wasps fed a sucrose solution. Likewise,

Syme (1975) found increased longevity of female Hyssopus

thymus Girault (Hymenoptera: Eulophidae) which had been

exposed to the plants Rumex acetosella L. (Polygonaceae)

and Hypericum perforatum L. (Hypericaceae), with exposure

to R. acefoseb also increasing fecundity. These results

suggest that R. crispus, Ii. denticulatum, and Solidago sp.

found in our study are potentially important food sources for

R. frustrana parasitoids.

Past studies have found intensive forest management

practices to be associated with increased tip moth

population fluctuations (Miller and Stephen 1983, Nowak

and Berisford 2000). Our study supported these results, with

infestation levels nearly twice as variable in treated plots

than in untreated plots, based on the coefficient of variation.

Further study is needed to verify this association and to

examine possible underlying causes.

The overall tip moth parasitism rate of ca. 50 percent found

in the vegetation control study generally agrees with those of

Freeman and Berisford (1979) (42 percent) for the Georgia

Piedmont and Eikenbary and Fox (1965) (41 percent) for the

South Carolina coastal plain, but is higher than that obtained

by the latter authors for the South Carolina Piedmont (26.0

percent). Among individual species, Hy. rhyacioniae

accounted for a significantly greater proportion of parasitism

in the herbicide-treated than the untreated plots. This

species may be less affected by microclimatic influences

than the others, or may be less subject to competition or

predation in the herbicide-treated plots. Tip moth infestation

rates were about 3.5 times higher in the untreated plots than

in the treated plots, but there was no significant difference in

parasitism rates between treatments, indicating that more

parasitism events occurred in the untreated plots. Malaise

trapping showed no difference in parasitoid abundance

between plots, suggesting a greater number of moths

parasitized per parasitoid in the untreated plots, a functional

response first described by Helling (1959). This response

could result from greater longevity of parasitoids due to more

food resources, less searching time per host due to higher

moth densities, or other factors. However, the much higher

infestation levels in the untreated stands suggest that

vegetation management practices do not necessarily affect

the role of parasitoids in tip moth population control.

The biological insecticides Btk and tebufenozide appeared

to have no effect on tip moth parasitism. The effects of

acephate were species-specific, with decreased parasitism

by Ha. rhyacioniae and relatively high parasitism by L.

mediocris. Lixophaga mediocris is a primary tip moth

parasitoid (Freeman and Berisford 1979). Generally,

Lixophage spp. parasitize stem borers by ovipositing at

openings made by the host. Larvae burrow through the

host’s frass and actively search for the host (Wood 1987).

This suggests that L. mediocris attack late instar tip moth

larvae, otherwise its eggs and larvae would be susceptible

to early application of a contact insecticide such as

acephate. Lixophaga mediocris adults are much larger and

more robust than adults of the three common parasitic

wasps captured in this study; this suggests that adults may

be more capable of surviving contact with insecticides

because of less surface to volume ratio. Lixophaga

mediocris has been found to be most abundant in

overwintering and spring tip moth generations in the Georgia

coastal plain (McCravy and Berisford 2000). Thus, acephate

would probably have less of an impact on overall tip moth

parasitism during these generations.

Haltichella rhyacioniae has been found to be a primary

parasitoid of tip moths in most studies, although one

individual was reared from L. mediocris by Freeman and

Berisford (1979). The low numbers of Ha. rhyacioniae in

acephate-treated plots suggest that this parasitoid may be

susceptible to this insecticide, either in the adult stage or

perhaps as a result of larval mortality if it attacks tip moths in

the early (targeted) larval stages. Ha/fiche/la rhyacioniae are

small chalcidids, from 2.8 to 3.6 mm in length (Yates 1967)

and their small size may contribute to their vulnerability to

acephate. The timing of attack of Ha. rhyacioniae is

unknown. This parasitoid is usually not a numerically

important part of the tip moth parasitoid fauna, accounting

for less than 10 percent of tip moth parasitism in most

regions (Eikenbary and Fox 1965, Freeman and Berisford

1979, Lashomb and others 1980, Miller and Stephen 1983,

McCravy and Berisford 2000) so high mortality of this

species might not have a great impact on tip moth

parasitism. The collection of large numbers of the

undescribed species of Temelucha was surprising, given the

numerous rearings of tip moth parasitoids done throughout

much of the moth’s range. This suggests that the species

composition of the tip moth parasitoid complex can vary

substantially even over relatively small geographic ranges.

This finding further illustrates that there is still much to be

learned regarding the parasitoid complexes of even relatively

well-studied and economically important forest insect pests.

Little work has been done regarding the effects of

tebufenozide on parasitoids. Jacas and others (1995) found

that oral doses reduced survival of Opius concolor Szepl.

(Hymenoptera: Braconidae) in a dose-dependent manner,

but had no effect on fertility. Tebufenozide treatment of

Mediterranean flour moth (fphestia kuehniella Zeller)

(Lepidoptera: Pyralidae) eggs parasitized by Trichogramma

pretiosum Riley (Hymenoptera: Trichogrammatidae) did not

significantly increase wasp mortality but did significantly

reduce subsequent parasitism by exposed females (Consoli

and others 1998). Potential effects on parasitism in the field

were not examined in either case. In our study neither

tebufenozide nor Btk had any effect on overall parasitism

rates or parasitism by individual species (figs. 1 and 2). Niwa

and others (1987) also found that B. fhuringiensis had no

effect on parasitism rates nor species distribution of

parasitoids of the western spruce budworm, Choristoneura

occidentalis Freeman (Lepidoptera: Tortricidae). However,

Hamel (1977) found increased larval parasitism of C.

occidentalis by parasitoids attacking early instars and

decreased parasitism by parasitoids attacking late instars

and pupae. These latter results were attributed to the

photonegative behavior of parasitized early instar larvae,

which apparently allowed them to avoid contact with the

insecticide. Tip moth larvae generally bore into a needle

base immediately after eclosion, and virtually the entire

immature period is spent within plant tissues (Berisford

1988). Little is known of the timing of attack by the various

3 1
tip moth parasitoids. Because first instar larvae are targeted

for insecticide treatment, only those attacking eggs or first

instar larvae would be subject to indirect mortality due to

death of the host. Those that attack later stages would suffer

little indirect mortality.

These studies further illustrate that larval/pupal parasitism

(40-50 percent) is an important source of tip moth mortality.

Herbicide treatments did not affect parasitism rates, and

infestation rates were highest in the untreated plots,

suggesting that use of herbicides does not affect the ability

of tip moth parasitoids to regulate moth populations.

However, the fact that total parasitism was higher in the

untreated plots raises the possibility that presence of greater

amounts of vegetation can benefit tip moth parasitoids.

Among the insecticides, the bioiogicals, Btk and

tebufenozide, had little or no impact on tip moth parasitoids,

but were less effective in controlling tip moth than acephate.

This is important since parasitism could reduce residual tip

moth populations when insecticidal control is incomplete.

The negative effects of acephate appear to be speciesspecific, meaning that overall effects on tip moth parasitism

could vary from region to region depending on variation in

the species composition of the tip moth parasitoid complex.

In generations or regions where L. mediocris is the dominant

tip moth parasitoid, this insecticide would probably have

relatively little effect on overall tip moth parasitism.

ACKNOWLEDGMENTS

We thank R. Garland, A. Coody, N. LeCroy, J. Smith, T.

Jackson, B. Dorough, M. Morrow, and D. Hart (University of

Georgia) for technical assistance. J. Seckinger, S. Cameron,

F. Bevan (Union Camp Woodlands Corp.) and B. Mewborn

(Weyerhauser Co.) were of great help in providing study

sites. K. Massengale (B and S Wood Services) applied the

insecticides, and J. Ghent (USDA Forest Service) assisted

with equipment calibration and monitoring of spray

deposition. R. Hedden (Clemson University), D. Miller (USDA

Forest Service), S. Salom (Virginia Polytechnic Institute and

State University), and J. Strazanik (West Virginia University)

provided helpful comments on various sections of the

manuscript. B. Haynes and M. Moore (University of Georgia)

provided assistance and advice with vegetation sampling

and plant identifications. L. Coote (Royal Ontario Museum),

C. Darling (Royal Ontario Museum), G. Gibson (Agriculture

and Agri-Food Canada), E. Grissell (USDA, Systematic

Entomology Laboratory), S. Heydon (University of CaliforniaDavis), J. Luhman (Minnesota Dept. of Agriculture), A.

Menke (USDA, Systematic Entomology Laboratory), M.

Schauff (USDA, Systematic Entomology Laboratory), A.

Sharkov (Ohio State University), D. Wahl (American

Entomological Institute), J. Whitfield (University of Arkansas),

M. Wood (Agriculture and Agri-Food Canada), and G.

Zolnerowich (Texas A&M University) provided positive

identifications of parasitoids. This study was supported by

the Pine Tip Moth Research Consortium and USDA Forest

Service Cooperative Agreement No. 42-98-0004.

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Nantucket pine tip moth Rhyacionia frustrana. Annals of the

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moth parasites to tree level, orientation and hosts per pine tip.

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Freeman, D. H., Jr. 1987. Applied categorical data analysis. New

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pine tip moth, Rhyacionia frusfrana (Comstock), and the pitch

pine tip moth, Rhyacionia rigidana (Fernald) (Lepidoptera:

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Garguillo. P. M.; Berisford, C. W.; Godbee, J. F. 1985. Prediction of

optimal timing for chemical control of the Nantucket pine tip

moth, Rhyacionia frusfrana (Cornstock) (Lepidoptera: Tortricidae)

in the southeastern coastal plain. Journal of Economic Entomology. 78: 148-154.

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Jervis, M. A.; Kidd, N. A. C.; Fitton, M. G.; Huddleston, T.; Dawah,

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pine tip moth (Lepidoptera: Tortricidae) in the coastal plain of

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on Nantucket pine tip moth (Lepidoptera: Tortricidae) populations

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cooperative effort at biological control of the Nantucket pine tip

moth. Arkansas Agricultural Experiment Station, Arkansas Farm

Research. 29: 8.

Warren, L. 0. 1985. Primary hymenopterous parasites of Nantucket

pine tip moth, Rhyacionia frustrana (Comstock). Journal of

Entomological Science. 20: 383-389.

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nearctic diptera, vol. 2. Ottawa, Canada: Canada Communication

Group: 1193-1269.

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species annotations. U.S. Department of Agriculture, Forest

Service, Southeastern Forest Experiment Station.

33
THE POTENTIAL FOR 7R/CHOG/?AMMA RELEASES TO

S ESS TIP MOTH POPULATIONS IN PINE PLANTATIONS

David B. Orr, Charles P.-C. Suh, Michael Philip,

McCravy, and Gary L. DeBarr’

Abstract-Because the Nantucket pine tip moth is a native pest, augmentation (mass-release) of native natural enemies

may be the most promising method of tip moth biocontrol. The tip moth has several important egg, larval, and pupal

parasitoids. Egg parasitoids are most effective as biocontrol agents because they eliminate the host before it reaches a

damaging stage. Trichogramma egg parasitoids are the most important of these, and are the most commonly augmented

arthropod in biocontrol programs worldwide. lnundative releases of encapsulated Trichogramma exiguum Pinto & Platner

were evaluated for suppression of R. frusfrana in first year loblolly pine, Pinus taeda L., plantations. Three releases of

328,238 + 88,379 -Q-/ha, spaced 7 d apart, were made in three 0.4 ha plots during second generation R. frustrana egg

deposition. The quality of each release was very high in comparison with published values of biological characteristics of T:

exiguum. Parasitism of R. frustrana eggs was significantly increased by 29 percent when compared to check plots, egg

survival (hatching) was significantly reduced by 47 percent, and larval populations were significantly reduced 60 percent.

There was no significant difference in the percentage of terminals damaged between 7 . exiguum-treated (31 f 16 percent)

and control plots (45 i: 10 percent), however, length of terminal damage was significantly lower in treated plots. The

percentage of damage to top whorl shoots was significantly lower in T: exiguum-treated plots compared with control plots.

but there was no significant difference in length of damage. Microhabitat significantly affected the number of consecutive

hours per day that were 35°C or above (critical temperature for preimaginal 7 : exiguum survival). Soil surface with no cover

had the greatest number of hours 35°C or greater, followed by soil surface with herbaceous cover, and canopies of small

trees (0.4 m tall). Canopy habitats in larger trees (0.9 - 1.8 m tall) had the most moderate temperature conditions. Parasitoid

emergence was significantly reduced in response to increasing number of consecutive hours 35°C or greater. Predation of

7 : exiguum prior to emergence, though relatively minor, was significantly affected by microhabitat and by the length of time

capsules were in the field before emergence (i.e. cohort number). The reduction of R. frusfrana populations by mass-release

of Trichogramma is technically feasible. In order to make these releases practical, however, we suggest several

considerations for future research. Large scale Trichogramma releases could be studied to evaluate possible area-wide

effects and residual effects over multiple tip moth generations. Combining several releases of Trichogramma into a single

application may be accomplished by a single release of multiple cohorts timed to emerge over a 7-8 day period. The

efficacy of such an approach should be studied. Consideration might be made of plantation management practices that

result in adequate vegetational cover for survival of encapsulated Tricbogramma broadcast on the soil surface, but do not

interfere with tree growth. Though unlikely with a native parasitoid, the potential for non-target impacts should be considered

in any future evaluations.

The purpose of this paper is to examine the potential for

using biological control as a practical pest management tool

for R. frusfrana in southeastern pine plantations. We briefly

review the literature on naturally occurring parasitoids and

predators of R. frusfrana, and the use of one parasitoid

group, Trichogramma, in pest management. We also

summarize data from a study demonstrating the efficacy of

Trichogramma releases and the suitability of microclimate in

pine plantations for Trichogramma survival. Finally, we

include a discussion of the research questions that should

be addressed in determining the potential for Trichogramma

releases to suppress R. frustrana in commercial pine

plantations

Biological Control and R. frusfrana

There are three general approaches to implementing

biological control in pest management systems. The first,

importation (or classical) biological control involves

importing effective natural enemies of exotic pests from the

pests’ homeland. However, R. frusfrana is a native pest, so

the classical approach does not apply to it. The so-called

“neo-classical” approach, in which natural enemies that

attack related pests in other geographic locations are sought

(Hokkanen and Pimentel 1989) might be considered.

However, the neoclassical approach is considered

ecologically risky and is frowned upon by some in the

conservation community (Simberloff and Stiling 1996).

i Orr, Assistant Professor, and Philip, Graduate Student, Department of Entomology, College of Agriculture and Life Sciences, North Carolina

State University, Raleigh, NC, 276957613; Suh, Research Entomologist, USDA ARS APMRU, 2771 F 8 ; B Road, College Station, TX 77845;

McCravy, Department of Entomology, University of Georgia, Athens, Georgia 30602-2603, and DeBarr, Research Entomologist [retired), USDA

Forest Service, Southern Research Station, Forestry Sciences Laboratory, Athens, Georgia 30602.

Citation for proceedings: Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.

3 4
Conservation biological control involves remediation of

factors in systems that limit the effectiveness of natural

enemies. This can involve activities as diverse as modifying

pesticide use practices or the creation of additional habitat

for natural enemies. The potential for conservation biological

control of R. frusfrana through pesticide use modification

appears low because of the limited range of insecticide

products available and the narrow and sometimes

unpredictable timing window for their application (Fettig and

Berisford 1999, McCravy 1998). In addition, resident

populations of natural enemies do not adequately suppress

R. frusfrana populations on their own (McCravy 1998). The

use of habitat manipulation to increase natural enemy

effectiveness may also be difficult. The intensive site

preparation and early chemical weed control employed to

increase survival and growth rate of seedling pines has

apparently resulted in higher tip moth densities. The levels of

associated vegetation in pine plantations has been shown to

be a factor that predisposes stands to tip moth damage

(Warren 1963, Berisford and Kulman 1967, Ross and others

1990). Berisford (1988) suggested that this relationship

might be due to variation in the availability of alternate hosts

or pollen and nectar sources for natural enemies. However,

McCravy (1998) demonstrated no relationship between

parasitism levels of R. frusfrana and vegetational diversity.

Augmentation biological control involves augmenting

populations of natural enemies not present in high enough

numbers to be effective, by means of releasing lab reared

enemies. This approach has been evaluated by Orr and

others (2000) and has been shown to be technically

feasible for R. frusfrana suppression in a study presented

below.

Natural Enemies of R. frusfrana in Pine Plantations

The concealed nature of R. frusfrana (i.e. small larvae mine

in needles and larger larvae tunnel into shoots) means that

larvae may not be as susceptible to predation, possibly

reducing the role predators play in natural regulation of tip

moth populations. However, there is a rich complex of over

60 parasitoid species that attack R. frusfrana eggs, larvae,

and pupae (Frank and Foltz 1997). Some of the parasitoids

attacking R. frusfrana may be important in regulating

populations of this pest (Berisford 1988).

Natural populations of Trichogramma spp. wasps are

responsible for most Rhyacionia frusfrana egg mortality.

Garguillo and Berisford (1983) found parasitism of R.

frusfrana eggs by Trichogramma to be as high as 47 percent.

Similarly, Yates (1966) found 64.5 percent egg mortality due

to I minufum Riley in central Georgia. McCravy and

Berisford (1998) reported 37.2 percent and 43.3 percent

parasitism of spring and summer generation eggs,

respectively. The species responsible for this parasitism

were identified as primarily T: prefiosum Riley and T exiguum

Pinto & Platner, with a small number of eggs attacked by T:

marfhae Goodpasture (McCravy 1998).

McCravy (1998) found overall pine tip moth larval and pupal

parasitism to be 44.8 percent on the Georgia coastal plain,

and Freeman and Berisford (1979) found 42 percent

parasitism on the Georgia Piedmont. Eikenbary and Fox

(1965) reported tip moth parasitism to 41 percent and 26

percent on the South Carolina coastal plain and Piedmont,

respectively. The species primarily responsible for tip moth

parasitism are the tachinid fly Lixophaga mediocris Aldrich,

the ichneumonid wasp Campoplex frusfranae Cushman, the

eurytomid wasp Eutyfome pini Bugbee, and the eulophid

wasp Hyssopus rhyacioniae Gahan (McCravy 1998).

As indicated above, one possible approach to biological

control of R. frusfrana in pine plantations is the

augmentation of natural enemies. Garguillo and Berisford

(1983) found that biotic mortality factors affecting R.

frusfrana are most important in the egg and pupal stages.

Since pupal mortality occurs after the trees are already

damaged, it seems logical to focus on the egg stage as a

target and Trichogramma wasps as a natural enemy for

augmentation.

Use of Trichogramma in Augmentation Biological

Control

Parasitic wasps in the genus Trichogramma are the most

commonly employed arthropod in augmentation biological

control programs. These parasitoids have several

advantages as biological control agents, including relative

ease of rearing and the fact that they kill their host in the egg

stage before it causes feeding injury (Wajnberg and Hassan

1994). Trichogramma releases are currently used to treat an

estimated 32 million hectares annually for control of

agricultural and forest pests (Li 1994) and are being studied

in over 50 countries worldwide (Smith 1996). Of the

approximately 180 species of Trichogramma known, over 70

have been employed as biocontrol agents, and 20 are

commonly mass reared and released in augmentation

programs (Li 1994, Pinto 1998). Individuals to be mass

reared are usually collected near the planned release site to

ensure that the Trichogramma are adapted to that area

(Smith 1996).

Trichogramma are exclusively egg parasitoids seldom

exceeding 0.7 mm in length (Pinto 1998). They have been

recorded from hosts in seven insect orders, but are

predominantly parasitoids of lepidoptera (Pinto and

Stouthamer 1994). Trichogramma have a worldwide

distribution and comprise the largest genus within the family

Trichogrammatidae (Pinto 1998).

Augmentation biocontrol with Trichogramma can take the

form of inundative or inoculative releases (ii 1994).

lnundative releases require the mass rearing and release of

many individuals to combat an existing pest problem.

Inoculative releases involve fewer individuals released early

in the cropping season to prevent pests from reaching

damaging levels. Many Trichogramma release programs are

actually a hybrid of these two release approaches.

Parasitoids are released inundatively only at the beginning

of the oviposition period of the targeted pest with the

expectation that their progeny will continue to provide pest

suppression through the remainder of the oviposition period.

Reducing the number of releases required for a single

generation of a pest makes this hybrid approach more

economical.

35
FEASIBILITY OF TRICHOGRAMMA RELEASES

FOR R. FRUSTRANA SUPPRESSION.

A study conducted in North Carolina in 1998 evaluated the

feasibility of using inundative releases of T: exiguum for

suppression of second generation R. frustrana in loblolly

pine, I? faeda L., plantations. This was the first study to

consider the augmentation of natural enemy populations for

R. frusfrana control.

Study Design and Plot Management

The experiment was set up using a complete block design,

with three field locations (each with a treatment and a

control plot) acting as three blocks. Two field locations were

near Connarista, North Carolina, and a third was near

Aulander, in Bertie County, North Carolina. The treatment

was 7: exiguum release: controls were not treated with T:

exiguum, and insecticides were not used on any of the plots.

Within each location, the Trichogramma release plot was at

least 400 m downwind (based on prevailing wind direction

for that area) from the control plot to reduce possibility of

parasitoid dispersal into control plots. Plots were

approximately 0.4 ha each.

Pinus faeda seedlings (1 - 0) were planted in rows spaced

3.5 m apart from furrow to furrow, and 1.7 m apart within

rows. Field locations 1 and 2 were planted on 23-27

January, 1997, and field location 3 on 31 Jan - 1 Feb, 1997.

All three locations received the following herbicide treatment

per ha: May, 97,946 ml Velpar LQ (hexazinone) and 89 ml

Oust@ (sulfoneturon) (banded on rows); June, 97, 118 ml

Arsenal@ (imazapyr) (broadcast), 0.74 kg Velpar DF8 and

89 ml Oust@ (broadcast).

Data Analysis

Tip moth egg, larval, and pupal counts were transformed by

taking the square root prior to analysis. These data and

damage data were analyzed using analysis of variance

(PROC GLM, SAS Institute, Cary, NC, USA, 1996). Hatch

and parasitism data were subjected to logistic regression

analysis (PROC GENMOD with PSCALE option and

likelihood ratio tests, SAS Institute, Cat-y, NC, USA, 1996).

Temperature, parasitoid emergence, and predation data

were analyzed using analysis of variance (PROC GLM, SAS

Institute, Cary, NC, USA, 1996). Parasitoid emergence data

were subjected to arcsine square root transformation prior to

analysis. The influence of temperature on T: exiguum

emergence was examined with a correlation analysis (PROC

CORR, SAS Institute, Cary, NC, USA, 1996).

R. frusfrana Population Sampling

At each of the three field locations, R. frustrana egg density

was estimated in release and control plots by clipping the

upper 22-25 cm section of 20 sub-terminal shoots (1 shoot

per tree) randomly selected from the central 50 percent of

the plot. Shoot samples were placed in Zip-lo& bags and

immediately taken to a laboratory where they were

examined for R. frustrana eggs. Total number of parasitized

and viable eggs were recorded for each plot. Shoots were

collected and examined every 3-4 d beginning 29 May.

Second generation R. frusfrana eggs were first detected

between 29 May and 1 June at all three field locations (data

for all release plots combined presented in fig. 1). At field

site 1, at peak oviposition R. frusfrana egg density in both T:

exiguum-treated and control plots was 2.2 eggs per shoot,

with both peaks occurring on 8 June. At field site 2, peak

oviposition in the T. exiguum-treated plot was 1.7 eggs per

shoot (5 June) and 2.3 eggs per shoot (8 June) in the control

plot. At field site 3, peak oviposition in the T: exiguum-treated

plot was 1 .O eggs per shoot (8 June) and 0.8 eggs per shoot

(8 June) in the control plot. Overall, there was no significant

difference in egg numbers (df=l,14, F=O.64, PzO.05)

between T: exiguum-treated and control plots, therefore data

from the three fields sites were combined.

Source, Release Rates, and Quality of

Trichogramma

Proper selection of species, biotypes or ecotypes has been

shown to be crucial for successful Trichogramma

augmentation (Kot 1979; Voronin and Grinberg 1981; Pak

1988). McCravy and Berisford (1998) reported that two

species responsible for R. frusfrana parasitism were T:

prefiosum and T: exiguum. We selected T exiguum because

prior experience had indicated this was a vigorous species

that retained very high quality under long-term mass rearing

(Suh and others 1998). To ensure we had a strain that was

well adapted to the area of intended release, we collected

material for our culture from a site near Plymouth, North

Carolina, within 50 km of release sites.

Trichogramma exiguum were reared from parasitized

sentinel corn earworm, Helicoverpa zea Boddie

(Lepidoptera: Noctuidae) eggs placed in woodlots adjacent

to agricultural fields near Plymouth, North Carolina. Eight

isolines (colonies begun from a single mated female) were

collected and species identity confirmed by John Pinto,

University of California at Riverside. Parasitoids were

shipped to BIOTOP (Valbonne, France) where isolines were

combined, mass reared, and formulated for field release.

The formulation consisted of waxed cardboard capsules

(approx. 5 cm3) each containing an average of 1319 f 140 T:

exiguum developing inside Mediterranean flour moth,

Ephesfia kuehniella Zeller, eggs. Four small holes made

during the encapsulation process were just large enough for

adults to escape but small enough to prevent most predators

from entering the capsules.

Shipments from BIOTOP to NCSU were made weekly, via

commercial air freight. Each of three weekly shipments

(beginning 25 May) consisted of three cohorts of parasitoids

whose development was staggered approximately 25

Celsius degree days apart. For each shipment, a HOBO

XT@ Temperature Logger (Onset Computer Corp., 536

MacArthur Blvd., Box 3450, Pocasset, MA 02559-3450)

programmed to record temperature hourly was placed

alongside capsules to monitor temperature fluctuations.

These temperature data allowed estimation of degree day

accumulation during shipping and handling so accurate

predictions of adult emergence could be made.

Three releases (RI - R3), spaced 7 d apart, were made in

each release plot beginning 29 May (fig. 1). Each release

contained three cohorts of capsules differing in 7: exiguum

development. One set of capsules contained T exiguum

expected to emerge within 12-24 h, the second within 60-
R I 2.0

R2 R3

Cohort 1

II Cohort 2

Cohort 3

-Eggs

/

1.8

1.6

0.6 &

0.4

0.2

Date

Figure I-Mean Rhyacionia frustrana eggs per shoot and mean number of Trichogramma exiguum released with date of peak

emergence for each cohort (three releases RI - R3, three cohorts each). Data presented are from all release plots combined.

Bertie County, NC, USA, 1998.

72 h, and the third within 96-108 h after field release.

Trichogramma capsules were hand-placed at 100 release

points evenly spaced throughout each releaseplot. Each

release point had a pair of waxed cone-shaped paper cups,

located 0.3 to 0.5 m above the soil surface in the tree

canopy, into which capsules were placed. Cups were spaced

approx. 5.5 m apart within rows and 7 m apart across rows.

T: exiguum were released at a rate of 328,238 Jo 88,379

females/ha/ cohort/release (determined from data presented

below and in fig. 1).

Stringent quality control protocols were followed once

material arrived in North Carolina to ensure that only high

quality T: exiguum were utilized in this study. Poor quality of

released natural enemies can lead to unsatisfactory pest

suppression and unpredictable results (Hoy and others

1991).

Samples of five capsules per T: exiguum cohort were frozen

immediately upon receipt to determine production

emergence (i.e. percentage of parasitized eggs added to

fresh eggs during production). Emergence percentages from

all subsequent samples were estimated by counting

emergence holes in 50 black (parasitized) eggs/capsule, and

subtracting production emergence. Trichogramma exiguum

adults from a second sample of IO capsules per cohort were

allowed to emerge over a seven day period at 25” C, 80

percent RH, and a 16L:8D photoperiod after which capsules

were frozen. For each of the 10 individual capsules,

emergence was estimated, 30 adults were randomly

selected to estimate sex ratio, and IO females were

randomly selected to estimate percent brachyptery. A third

sample of 5 capsules per cohort was used to estimate

female longevity according to procedures described by

Cerutti and Bigler (1991).

To estimate field release rates, a fourth sample of 10

capsules per cohort was taken just prior to each release,

and the total number of parasitized (blackened) eggs per

capsule was counted. To assess field emergence (i.e. timing

of releases), a fifth sample of 25 capsules per cohort was

hand-placed in waxed cone-shaped paper cups located 0.5

m above the soil surface in the tree canopy, adjacent to a

release plot. Five capsules from each cohort were collected

on the day of release (day 0), 3, 5, 7, 10, and 11 d after each

release, and frozen until they could be sampled.

Mean (+ SD) T. exiguum emergence under laboratory

conditions for released cohorts was 96 f 2 percent,

consisting of 74 f 3 percent females, of which 1 zf: 1 percent

displayed brachyptery. Female longevity for released cohorts

averaged 18 rt 3 d. In comparison, the mean life span of

adult female T. exiguum reported in other laboratory studies

ranged from 4.1 to 8.6 d (Harrison and others 1985, Ram

3 7
and lrulandi 1989). Mean emergence of parasitoids under

field conditions was 96 rt 4 percent. A release rate of

328,238 ~fr 88,379 females/ha/cohort/release was estimated

after taking into account the number of parasitized E.

kuehniella eggs per capsule, percent of females emerging

from capsules, removal of brachypterous females, and

emergence of parasitoids under field conditions (fig. 1). Peak

emergence of parasitoid cohorts from the three releases

occurred every 1 to 4 days throughout the peak oviposition

period of R. frustrana (fig. 1).

Parasitism of R. frusfrana Eggs

The level of egg parasitism in 7. exiguum release and check

plots was measured on 1, 5, 8, 12, and 15 June. For each

date, R. frustrana eggs were collected from shoots used to

estimate egg densities. To standardize parasitism data, only

light orange-colored eggs (2-3 d-old) were clipped from

shoots and used to determine percent parasitism. Clipped

eggs (1 O-35 eggs per plot) were placed on premoistened

filter paper (Qualitative P5, 5.5 cm diam.) within petri dishes

(6 cm diam.) and held at 25°C 80 percent humidity, and a

16L:8D photoperiod for 7-8 d at which time eggs were

classified as either hatched, black-head stage, non-viable, or

parasitized. A percentage was calculated for each category.

Parasitism of R. frusfrana eggs collected throughout the

study period was significantly increased by 29 percent

(F,,,,=8.30, P=O.O16) and egg hatch was significantly

reduced by 47 percent (F, ,=62.0, P<O.OOl) in T: exiguumtreated plots (combined) compared with control plots

(combined) (table 1). The species responsible for parasitism

in T. exiguum-release plots were T exiguum (100 percent of

parasitized eggs collected), and in control plots T: exiguum

(92.4 percent), T marthae (3.8 percent), T: pretiosum (1.9

percent), and T minutum (1.9 percent). Parasitism in control

plots was approximately 42 percent (table 1) which seems

relatively high, but is in line with the 43.3 percent parasitism

of summer generation R. frusfrana eggs by resident

populations of T exiguum, T: pretiosum, and T: marthae in

Georgia pine plantations reported by (McCravy and

Berisford 1998).

Larval infestation

During shoot examinations for eggs, numbers of instar 1-2,

3-4, 5 larvae (determined by head capsule size; see Fox

and others 1972) and pupae found in shoots and needles

were recorded for each release and control plot. The number

of larvae in instar categories 1-2, 3-4, and 5 per shoot was

significantly lower in T: exiguum-treated plots compared to

control plots (df=l,14, F=51.41, P=O.OOOl; df=l,14,

F=16.79, P=O.O004; df=l,14, F=26.02, P=O.OOOl), with a

mean (& SD) reduction in 7: exiguum-treated plots of 65 rtr 8

percent, 63 f 10 percent, and 57 f 4 percent, respectively

(fig. 2). The number of pupae per shoot was also significantly

(df=l, 14, F=6.91, P=O.O2) reduced by 62 f 30 percent in

treated plots.

Population levels of R. frustrana were high in all plots used

in this study (see fig. 2) presenting a challenging

environment in which to test augmentation of natural

enemies for suppression of this pest. The percentage

decrease in egg survival, and the percentage reduction in

neonate and fifth instar larval numbers all had approximately

the same absolute value (47 percent, 65 percent and 57

percent, respectively). This suggests there was no

compensatory mortality in the larval stage during this study.

This is an important consideration since compensatory

mortality in larval stages followed Trichogramma releases in

rice (Van Hamburg and Hassell 1984) and cotton (Suh and

others 1998). Andow and others (1995) found a direct

relationship between egg mortality and larval mortality in

corn. Although there are few studies addressing this

concern, the variability in results suggests that the issue of

compensatory mortality should be addressed in each

system in which Trichogramma populations are to be

augmented.

Damage to trees

The number of mined needles and percentage of shoots

damaged was also recorded while shoots were examined for

eggs. A final shoot damage assessment was made on 20

July in each release and control plot. For each plot, 50 trees

were randomly selected from the central 50 percent of the

plot. Each tree was divided into three sections (terminal

shoot; top whorl shoots; and remaining tree shoots), all

shoots were sampled, and the length of damage in shoots

within the first two sections measured with a ruler.

Despite significant reductions in larval numbers, no

significant difference in percentages of terminal damage

Table I-Mean f SD percent parasitism and egg hatch of second generation

Rhyacionia frusfrana eggs collected from T. exiguum-treated and control $lots

in Pinus faeda plantations, June I-15, 1998 in Bertie County, NC

Percentage of R. frustrana eggs which were:

Plot type n Parasitized Hatched Non-viable

T: exiguum release 287 53.7 f 12.2 a 22 f 4b 24 rt IOa

Control 241 41.6 f 20.8 b 41 26a 17 f 13a

Values within a column followed by different letters are significantly different (logistic

regression, Plr: 0.05).

3 8
2.0 ,

i

T. exiguum - 1st - 2nd instar

1.5 u

*Q release I

\

- - - 3rd - 4th instar

I

\ -5th instar

a

I

1.0 p

\

1

2.0

9 Control * \

1.5 -- f \

C J \

I

b

L m 0’ I I , 1.0 -- \

I \

I I ‘L \

I

I \

Date

Figure 2-Mean number of Rhyacionia frustrana eggs, larvae, and pupae per shoot in Trichogramma exiguum release plots

and control plots. Bertie County, NC, USA, 1998.

(df=l,2, F=l.28, P=O.376) was found (table 2). However, top whorl shoots that were attacked (df=l,2, F=28.36,

there was a significant difference in the length of tunneling P=O.O34). However, there were no significant differences in

damage within terminals (df=1,2, F=5.69, P=O.O19). No the length of tunneling within top whorl shoots (df=l,2,

significant difference was found between release and control F=l.70, P=O.322). There were no significant differences

plots in the number of top whorl shoots (df=l,2, F=l.O4, betyeen release and control plots in the number of shoots

P=O.416), but there was a significant difference in number of below the top whorl (df=l,2, F=O.28, P=O.651), but the

39
Table 2-Mean It: SD percent of Pinus taeda shoots attacked by second generation Rhyacionia

frusfrana and length of tunneling in shoots occurring on different parts of trees= at three field

sites. Bertie Co., NC, USA, 1998

Shoots attacked on Length of tunneling

Remainder

Treatment Terminal Top whorl of tree Terminal Top whorl

_ _ _ _ _ _ _ _ _ _ _ _ _ Percent _ _ _ _ _ _ _ _ _ _ _ _ _ ---------Cm---------

71 exiguum release 31 f 16 30*4a 33i4a 2.3 k 1.3 a 1.8 i 0.3 a

Control 45*lOa 49*7b 53+3b 3.5 + 2.5 b 2.1 rt 0.2 a

Values within a column followed by different letters are significantly different (ANOVA, P <0.05)

a Fifty trees were sampled in each plot; data presented are averaged from 150 trees each for the T: exiguum release

and control plots.

number of these shoots that were attacked was significantly

lower in T. exiguum plots (df=l,2, F=5.48, P=O.144) (table 2).

Microclimatic effects on T: exiguum

In addition to assessing efficacy of 7. exiguum releases, we

also assessed T: exiguum application methodology by

monitoring temperature, 7: exiguum emergence, and

predation of T: exiguum in six distinct microhabitats found

within first and second year pine plantations. One-year-old

trees used for this study were in field location 1 used in the

release study. The two-year-old trees were located adjacent

to field location 1, and were planted 1 March, 1996 on the

same spacing described in the release study. The stand

received the following herbicide treatments: April 96, banded

946 ml Velpar L@ and 89 ml Oust@; June 96, broadcast 118

ml Arsenal@; April 97, broadcast 946 ml Velpar L@ and 89 ml

Oust@; June 97, broadcast 118 ml Arsenal@.

The microhabitats studied were: 1) soil surface with no cover

in 1”’ year plantation: 2); soil surface with herbaceous cover

in Is’ year plantation 3) canopy (mid-height) of small (0.46 m)

Is’ year plantation trees; 4) canopy (mid-height) of tall (0.92

m) 1”’ year plantation trees; 5) canopy (mid-height) of Znd

year plantation trees; 6) soil surface with herbaceous cover

in Znd year plantation. Temperature was monitored in each

habitat with a datalogger (Model CRIO, Campbell Scientific,

Inc., 815 W. 1800N, Logan, Utah 84321-1784) with 24

temperature probes (Model 107 on 100 ft. wire leads) set up

in between the stands of I- and 2-yr-old f? taeda. Each

temperature probe was completely enclosed within a sheath,

constructed from the cardboard used to encapsulate

Trichogramma, in order to simulate conditions inside

capsules. Probes were placed in the six microhabitats,

replicated four times (total of 24 sites). The datalogger was

programmed to take one measurement every minute and

record the average on an hourly basis for each temperature

probe. Measurements were begun 29 May, and continued

through 19 June. The critical temperature at which T:

exiguum survival is reduced is 35°C (Harrison and others

1985). We therefore calculated the number of consecutive

hours each day that were at or above this temperature.

To assess the effect of microclimate on T: exiguum

emergence in the different microhabitats, two capsules from

each cohort for two releases (I*’ and 3”1) were placed in

white nylon mesh bags alongside probes. In the canopy,

capsules were placed in cone-shaped waxed paper cups

used for the release study. One cohort was programmed to

emerge within 12-24 h, the second within 60-72 h, and the

third within 96-l 08 h after field release. Capsules from

cohorts 1 - 3 were collected 7, IO and 14 d, respectively,

following field release and then were immediately frozen.

The emergence percentage for each capsule was

determined using procedures described in the quality control

section. The first set of capsules was placed in the field on

29 May, and the second set on 12 June.

Microhabitat had a significant influence on the number of

consecutive hours per day that were 35°C or above (F, ,8=

3.34, P = 0.025) (table 3). This value varied significantly

between the two releases for which microclimate data were

collected (F, ,8= 9.56, P = 0.006) therefore subsequent

analyses were conducted on the two releases separately

(table 3). During the first release period (May 29 - June 5)

the bare soil surface had the greatest number of hours

35°C or greater, followed by the two soil surface

microhabitats with herbaceous cover and the 0.4 m tree

canopies. The two canopy habitats in the largest trees had

the most moderate temperature conditions. During the

second release period (June 12 - 19) temperature

conditions were more moderate due to cloudy weather and

the soil surface with no cover had significantly greater

number of hours 35°C or greater when compared to all

other microhabitats.

Parasitoid emergence (all microhabitats combined) was

significantly reduced in response to increasing number of

consecutive hours 35°C or above (Pearson’s Correlation

Coefficient = -0.673, P = 0.0001) in the first release period,

but was not significantly reduced in the second period

(Pearson’s Correlation Coefficient = -0.191, P = 0.23) (table

3).

4 0
Table 3-Mean f: SD microhabitat temperatures, and emergence and predation of encapsulated Trichogramma exiguum

exposed to various microhabitats within Pinus faeda plantations. Bertie County, NC, USA, 1998

Exposure

period Microhabitat description

Successive hrs (f SD)

above lethal temperature

(35” C) per day

T. exiguu Predation of

emergence T. exiguum

- - - - - - - - - -_ Percent _ _ _ _ _ _ _ _ _ _ _

May 29- 1styr. trees, soil surface, no cover 5.2 f 3.0 c 47.8 f 37.3 a 0.0 * 0.0 a

June 5 1”’ trees, soil surface, herbaceous yr. cover 1.5 f 2.4 b 68.3 f 31.5 ab 16.7 f 32.6 a

19’ 0.4 m trees, yr. canopy 0.9 zk 1.0 b 90.5 f 11.3 b 25.0 f 33.7 a b

1”’ 0.9 m trees, yr. canopy 0.3 f 0.3 a 95.0 rt 6.9 b 8.3 f 19.5 a

2nd yr. 1.8 m trees, soil surface, herbaceous

cover 1.6 f 2.5 b 98.2 f 2Zia 55.0 f 49.7 b

2nd 1.8 m trees, yr. canopy 0.4* 0.6 a 94.2 f 6.7 b 4.2 it 14.4 a

June 12-19 1”’ trees, soil surface, no cover yr. 3.9 f 2.5 b 82.6 f 31.5 a 8.3 rt 19.5 a

Is’ trees, soil surface, herbaceous yr. cover 1.0 * 1.9 a 91.8 A 9.1 a 16.7 rf: 24.6 a

1s’ 0.4 m trees, yr. canopy 0.4 f 0.6 a 90.7 f 12.8 a 16.7 i 32.6 a

1” 0.9 m trees, yr. canopy 0.1 * 0.2 a 89.9 i 11.5 a 4.2 f 14.4 a

2nd yr. 1.8 m trees, soil surface, herbaceous

cover 0.8 f 1.0 a 78.6 f 28.ga 58.3 f 46.9 b

2nd 1.8 m trees, yr. canopy 0.1 f 0.2 a 97.2 f 4.5 a 22.7 k 34.4 a b

yithin a given date, values within a column followed by different letters are significantly different (LS Means, P 10.05).

Heavy predation resulted in too many missing data points for PROC GLM to estimate a comparative value.

Predation of T. exiguum capsules

Predation of parasitized E. kuehniella eggs within capsules

was also noted while emergence data were being recorded.

Predation was either very heavy (c 100 eggs remaining in a

capsule) or not present. When both capsules of a pair had

heavy predation, we recorded 100 percent predation for the

pair: if only one capsule had heavy predation, 50 percent

was recorded; if neither capsule had obvious predation, 0

percent was recorded. Ants collected from inside capsules

were identified to genus by David Stephan, Dept. of

Entomology, North Carolina State University, USA.

Predation by ants in the genus Crematogaster was

significantly affected by microhabitat (F,,,= 3.30, P = 0.027);

the soil surface in second year plantations with herbaceous

ground cover had significantly more predation than the other

microhabitats (LS Means, P f 0.05) (table 3). The length of

time capsules were in the field before T: exiguum emergence

(i.e. cohort number) also significantly affected predation

(F,,,,= 16.3, P < O.OOl), but not emergence (F,,,,= 2.71, P =

0.075). Capsules in the third cohort that had been in the field

6 d prior to parasitoid emergence had significantly higher

predation than those exposed for 2 or 4 d (LS Means, P f

0.05) (table 4).

Predation in this study reduced the number of Tiichogramma

available for emergence in field plots, thereby reducing the

actual numbers of wasps/ha considerably below those

originally planned. Ants of the genus Crematogaster

appeared to be responsible for this predation, since they

were the only potential predators found inside capsules from

which predation was noted. The ants apparently gained

entry to the capsules by chewing the perimeter of and

widening the holes that are punched in capsules during

production to allow Trichogramma escape in the field.

Although the potential impediment of predation has been

noted in other Trichogramma release projects (Smith 1996)

none utilized encapsulated material as in this study.

Significant predation was not observed in cotton or apples

following release of encapsulated 7: exiguum (Suh and

others 1998, Shetty 2000) nor in corn when encapsulated T:

brassicae were released (Kabiri and others 1990, Orr 1993).

SUMMARY OF FEASIBILITY STUDY

Larval R. frustrana populations were reduced considerably

by T: exiguum in this study. However, the percentage

infestation of top whorl shoots was not as greatly reduced.

This reflects the fact that there were multiple larvae in

infested shoots in control plots, and therefore a reduction in

larval numbers did not necessarily lead to a proportional

reduction in number of infested shoots. There was, however,

a significant reduction in the length of damage within shoots.

This, plus the apparent lack of compensatory mortality,

indicates that Trichogramma release for suppression of R.

frustrana populations is technically feasible. Additional

studies will be required to evaluate the potential of this

technology to be used on an operational basis. Some

possible considerations for these studies are presented

below.

4 1
Table d-Mean i: SD emergence and predation of Trichogramma exiguum following

varying periods of exposure to field conditions within Pinus faeda plantations. Bertie Co.,

NC, USA, 1998

Exposure

period

No. days T: exiguum exposed to

field conditions prior to emergence

T exiguum

emergence

Predation of

T exiguum

May 29-

June 5

June 12-19

_ _ _ _ _ _ _ _ _ _ Percent_ _ _ _ _ _ _ _ _ _

86.4 f 24.5 a 10.4 f 25.4 a

79.1 f 26.8 a 4.4 + 20.9 a

75.0 + 34.2 a 37.0 c 40.5 b

89.6 - + 21.4 a 13.0 f 31.0 a

92.5 k 15.7 a 22.9 zf: 36.1 a b

85.1 k 18.1 a 27.1 k 36.1 b

Within a given date, values within a column followed by different letters are significantly different (1s Means,

P <0.05).

FUTURE RESEARCH CONSIDERATIONS. To date, a relationship between vegetational diversity in pine

There are a variety of questions that should be addressed plantations and natural enemy activity has not been

before an operational Trichogramma release system could demonstrated (McCravy 1998). However, egg parasitoid

be implemented. For example, release plots in this study longevity and parasitism of target pests can be substantially

were each 0.4 ha, and were surrounded by large untreated increased by the presence of nectar-bearing plants and/or

portions of the study plantations. Releasing Trichogramma honeydew in some agroecosystems (Orr 1988). In the

on a much larger scale, for example on an entire plantation, current study we found that ground cover and its effect on

would allow an evaluation of whether R. frustrana microclimate significantly influenced emergence of released

suppression can be improved by area-wide treatment effects parasitoids. Consideration of pine plantation management

over multiple generations. Such area-wide effects have been practices, their effect on ground cover, and the subsequent

demonstrated for other biologically-based pest management impact on Trichogramma releases may lead to improved

tactics such as mating disruption with semiochemicals (Niwa Trichogramma performance, and overall control of R.

and others 1988, Card& and Minks 1995). frustrana.

An examination of temperatures and T: exiguum emergence

within various microhabitats of pine plantations in the

feasibility study revealed significant differences in survival of

5: exiguum in the different microhabitats. The canopy of both

first and second year trees was the most suitable

microclimate for T: exiguum emergence. However,

distributing capsules into tree canopies would not be a

practical way to release Trichogramma in large pine

plantations. Likely, the most acceptable means of distribution

would be broadcast application by helicopter. Capsules

distributed in this manner would probably end up on the soil

surface. Where the soil surface was bare in our study,

Trichogramma capsules distributed on the soil surface faced

considerable reductions in emergence. We also found that

the longer capsules remained in the field prior to adult

emergence, the lower the emergence. This could be

especially important since in order to make Trichogramma

releases practical, only one application (containing several

cohorts that would emerge over a 7-8 d period) could be

made per R. frustrana generation. Future considerations for

optimizing the success of T;khogramma release

methodology in pine plantations should include a

consideration of the possible selection of high temperature

tolerant strains, and an examination of various types of

vegetational management on microhabitat and

Trichogramma emergence.

The predation of T exiguum by ants in our study may have

been due to the high numbers of capsules clustered in cups

or on the ground as part of our experimental design.

Encapsulated Trichogramma are usually broadcast, so that

they would have a uniform rather than clumped distribution.

It would be of value to assess broadcast application of

capsules on the ground versus clumped distribution (as in

this study) as a method of reducing predation.

Another consideration that should be made prior to

commercial implementation is the potential for Trichogramma

releases to have non-target impacts. Historically, biological

control has enjoyed a reputation as an environmentally safe

alternative to chemical. Recently, however, concern has

been raised regarding potential non-target impacts of

biocontrol practices (Follett and Duan 1999). Although the

focus of most attention is on the introduction of non-native

organisms in classical biocontrol programs, the

augmentation of native natural enemies may also a concern

(Orr and others 1999).

Because non-target impacts are of greatest concern outside

the release area, dispersal ability of Trichogramma is a key

component of potential non-target impacts. Studies on

dispersal of Trichogramma have demonstrated contradicting

results. Most studies indicate that Trichogramma dispersal is

limited (Bigler and others 1989, McDougall and Mills 1997).

4 2
However, Stern and others (1965) demonstrated that

individuals could travel up to 1100 m from the release site.

Bigler and others (1990) found that levels of parasitism by

Trichogramma evanescens of Ostrinia nub/a/is eggs placed

400m downwind of the point of parasitoid release were

equal to parasitism at the release site. These results led to

the conclusion that the effective release area for these

parasitoids was at least twice the area of the plot releases

were made in.

Host specificity is another key component to understanding

potential nontarget impacts. Parasitoid species in the genus

Trichogramma are considered highly polyphagous, together

attacking more than 400 species in 203 genera, 44 families,

and 7 orders (Pinto 1998, Bao and Chen 1989). However,

individual species tend to have narrow host and habitat

preferences or climatic tolerances, making them less likely to

cause undesired impacts (Orr and others 1999).

Future studies of Trichogramma releases in pine plantations

should consider the dispersal of parasitoids, and the

potential impact of releases on both predatory and

herbivorous species within and downwind of release sites.

This could be done by estimating parasitism of selected

species’ eggs when they are placed within plantations and in

surrounding habitats into which Trchogramrna could

potentially disperse.

ACKNOWLEDGMENTS

We thank R S Cameron and M Davidson, Union Camp

Corporation, for their assistance in locating the sites for this

study. This research was funded in part by the Pine Tip Moth

Research Consortium: Champion International Corporation;

International Paper Corporation; Smurfit-Stone Container

Corporation: Union Camp Corporation; USDA Forest

Service, Southern Research Station: The Timber Company;

and Weyerhaeuser Company. Helpful comments on an

earlier version of this manuscript were provided by F. Hain, F.

Hastings, and C Nalepa. We are grateful to F Kabiri and J

Frandon (BIOTOP, Valbonne, France) for rearing and

formulation of Trichogramma, and J Shurtleff (NCDA&CS

Quarantine Lab) for handling shipments.

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Orr, D. B.; Suh, C. P.-C. 1999. Parasitoids and predators. In: Rechcigl

J. E.; Rechcigl, N. A., editors. Biological and Biotechnological

Control of Insect Pests. Ann Arbor, Ml. Ann Arbor Press. 3-34.

Orr, D. B.; Garcia-Salazar, C.; Landis, D. A. 1999. Tdchogremma

non-target impacts: a method for biological control risk assessment. In: Follett, P.; Duan, J., editors. Non-target effects of

biological control. Kluwer Academic Publishers, Boston.

111-126.

Orr, D. B.; Suh, C.P.-C.; McCravy, K.W.; Berisford, C. W.; DeBarr,

G. L. 2000. Evaluation of inundative releases of Trichogramma

exiguum (Hymenoptera: Trichogrammatidae) for suppression of

Nantucket pine tip moth (Lepidoptera: Tortricidae) in pine

(Pinaceae) plantations. Canadian Entomologist. 12: 373-386.

Pak, G. A. 1988. Selection of Trichogramma for inundative biological

control. Ph.D. dissertation, Wageningen. Netherlands.

Wageningen Agricultural University. 224 p.

Pinto, J. D.; Stouthamer, R. 1994. Systematics of the

Trichogrammatidae with emphasis on the Trichogramma. In:

Wajnberg, E.; Hassan, S.A., editors. Biological control with egg

parasitoids. Wallingford, U.K., CAB International. l-36.

Pinto, J. D. 1998. Systematics of the North American species of

Trichogramma Westwood (Hymenoptera: Trichogrammatidae).

Memoirs of the Entomological Society of Washington No. 22.

287 p.

Ram, A.; Irulandi, V. 1989. Influence of host egg on biology of

Tfichogramma exiguum Pinto, Platner, and Oatman

(Trichogrammatidae: Hymenoptera). Indian Journal of Entomology 51: 361-365.

Ross, D. W.; Berisford, C. W.; Godbee, J. F., Jr. 1990. Pine tip moth,

Rhyacionia spp., response to herbaceous vegetation control in

an intensively site-prepared loblolly pine plantation. Forest

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SAS Institute. 1999. SASlSTAT user’s guide, release 7.1. Gary, NC.

SAS Institute. 3365 p.

Schultz, R. P. 1997. Loblolly pine (finus taeda L.): The ecology and

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D.C. USDA Forest Service. 494 p.

Shetty, P 2000. Assessment of Trichogramma wasps as biological

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Carolina State University.

Simberloff, D.; Stiling, P. 1996. How risky is biological control?

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Stem, V. M.; Schlinger, E. I.; Bowen, W. R. 1965. Dispersal studies of

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1098-1101.

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D.C. USDA Forest Service. 7 p.

4 4
USE OF PHEROMONE TRAPS TO PREDICT INFESTATION LEVELS OF

THE NANTUCKET PINE TIP MOTH: CAN IT BE DONE?

Christopher Asaro and C. Wayne Berisford’

Abstract-Pheromone traps baited with synthetic baits are used in southeastern pine plantations to monitor the phenology

of the Nantucket pine tip moth (Rhyacionia frustrana (Comstock)) for timing of insecticide applications. Trap catches of tip

moths have been difficult to interpret because they decrease considerably relative to population density from the spring

through subsequent generations. Understanding this pattern is important for optimizing trap usage and catch interpretation.

Decreased adult longevity during summer was demonstrated and suggested as the primary reason for low catches in hot

weather. In addition, methods were developed to utilize pheromone traps for predicting future population density and

damage by this pest. Trap catch was strongly correlated with tip moth density and damage within generations. Additionally,

trap catch of overwintering moths was a strong predictor of tip moth damage during the subsequent generation.

INTRODUCTION

Currently, pheromone-baited traps are used to capture

Nantucket pine tip moth, Rhyacionia frusfrana (Comstock),

for the following purposes: 1) to monitor seasonal activity or

phenology (Berisford 1974a, Berisford and others 1992,

Canalos and Berisford 1981, Ross and others 1989); 2) to

monitor daily activity and behavior (Berisford 1974b,

Berisford 1977, Berisford and Hedden 1978, Berisford and

others 1979, Canalos and others 1984, Webb and Berisford

1978); and 3) for the initiation of a spray-timing model

through the accumulation of degree days (Berisford and

others 1984, Fettig and Berisford 1999, Fettig and others

1998, Gargiullo and others 1984, Gargiullo and others 1985,

Kudon and others 1988). To date, however, traps have not

been used for predicting population density or damage. This

would be a powerful tool, enabling managers to make

control decisions regarding the next generation based on

trap catch data from the current generation of emerging

adult moths. Some studies attempting to positively correlate

trap catch with insect density or damage have not been

successful (Miller and McDougall 1973, Howell 1974,

Srivastava and others 1992). One hypothesis frequently

cited to explain this is called the “competition effect”, which

states that as an insect population increases, the number of

females in that population will increase and compete with

the baits (either sex pheromones or host volatiles) being

used in traps (Garde 1979, Knipling 1979). Nevertheless,

many have attempted such studies due to the obvious

potential benefits to a pest management system. Promising

studies in which some measure of population density or

damage has been positively correlated with pheromone trap

catch include some important forest pests such as the

Douglas-fir tussock moth, Orgyia pseucfotsugata

(McDunnough) (Daterman and others 1979) spruce

budworm, Chorisfoneura fumiferana (Clemens) (Allen and

others 1986) and gypsy moth, Lymantria dispar (L.) (Gage

and others 1990, Thorpe and others 1993) as well as some

agricultural pests such as the boll weevil, Anfhonomus

grandis grands (Boheman) (Johnson and Gilreath 1982)

and corn earworm, Hekoverpa zea (Boddie) (Latheef and

others 1993, Drapek and others 1997). The Nantucket pine

tip moth is one forest pest for which a sophisticated IPM

system is feasible given its importance to intensive forestry,

the similarities of intensive forestry to agricultural systems

during that portion of the rotation for which tip moths are a

problem, and the amount of research that has been devoted

to this pest. Therefore, it would seem logical to attempt such

a study for the Nantucket pine tip moth.

Before trap catches can be correlated with populations, an

important aspect of seasonal tip moth trap catch patterns

must be addressed. Tip moths are multivoltine, with three or

four generations per year in most of the Southeast (Fettig

and others 2000a). If trap catch patterns over an entire

season are examined, it is clear that trap catch is not well

correlated with density across generations. Typically, trap

catches decrease substantially from the first (spring) to the

second (early summer) and third (late summer) generations

in the Georgia Piedmont, even if tip moth populations

increase during that period (figs. l-4). Only in cases where

populations increase by four or five fold from spring to

summer is their similarity in trap catch between these

generations (fig. 2A). It is clear that trap catch and

population density across generations are not well

correlated. Will this effect our ability to make population

predictions?

Four hypotheses have been proposed to explain the

phenomenon of decreasing trap catches during the summer

generations: 1) The efficacy of pheromone baits decreases

rapidly during the summer due to increasing volatility of the

pheromone blend at high temperatures. This hypothesis has

been rejected since weekly bait replacement during this

study failed to increase summer trap catches, and baits have

f Asaro, Postdoctoral Research Associate, and Berisford, Research Professor, Department of Entomology, 413 Biological Sciences Building,

University of Georgia, Athens, GA 30602.

Citation forproceedings: Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.

4 5
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Figure l-Average number (&SE) of R. frusfrana males caught in

traps and the associated populations density prior to adult

emergence from February through September, 1997 at two sites in

Clarke and Morgan counties, Georgia A) Harve Mathis Road and B)

Bostwick.

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Figure 2-Average number (&SE) of R. frustrana males caught in

traps and the associated populations density prior to adult

emergence from February through September, 1998 at three sites

in Oglethorpe county, Georgia A) Lexington, B) Maxeys and C)

Arnoldsville.

Jultan Date

Figure 3-Average number (&SE) of R. frusfrana males caught in

traps and the associated populations density prior to adult

emergence from February through September, 1999 at three sites

in Oglethorpe county, Georgia A) Lexington, B) Maxeys and C)

Arnoldsville.

Julian Date

Figure 4-Average number (*SE) of R. frustrana males caught in

traps and the associated populations density prior to adult

emergence from February through September, 2000 at two sites in

Oglethorpe county, Georgia A) Lexington and B) Wilkes Farm.

4 6
been shown to have maximum attractancy during summer

for up to three weeks (Personal communication. Gary L.

Debarr. 1997. Southern Research Station, Forestry Sciences

Lab, 320 Green St., Athens, GA 30602). 2) Female moths

compensate for high summer temperatures by adjusting the

pheromone component ratio (2O:l blend of ES-dodecenyl

acetate and E9,l I-dodecadienyl acetate). Because each

pheromone component has a different volatility, under high

temperatures, one component may evaporate quicker than

the other, changing the ratio significantly to render the baits

less effective than competing females. Asaro and others

2001 have shown that there is no significant deviation from

the 2O:l ratio in Nantucket pine tip moth pheromone with

moths collected from the first and second generation in the

Georgia Piedmont and coastal plain. 3) During high

summer temperatures, male moths have more difficulty

locating and following pheromone plumes due to greater

heat convection. This hypothesis will not be explored in this

discussion. 4) Adult life span decreases during summer

due to high summer temperatures, thereby decreasing the

probability of catching any given moth during a specific time

period. An experiment designed to test this hypothesis is

discussed below.

TIP MOTH ADULT LIFE SPAN DURING DIFFERENT

GENERATIONS-METHODS

Adult Longevity-Field Experiment

For each of three tip moth generations during March, June,

and August 1997 and 1998, adults were reared from clipped

pine shoots and collected as they emerged in cages. Up to

five newly-emerged moths were placed in waxed paper cans

(473 ml, 8.44 cm diameter, Fonda Group Inc., Union, NJ)

with each circular end punched out and replaced by a fine

mesh material (Saran screen, 12.8 x 12.8 holes / sq cm,

Synthetic Industries, Cornelia, GA). Each paper can was

placed in a Pherocon 1 C@ sticky trap (Trece Inc., Salinas,

CA) to protect the moths from the elements and ant

(Hymenoptera: Formicidae) predation. In 1997, all traps

containing cans and moths were hung from trees in a fiveyear-old loblolly pine (Piffus taeda L.) plantation in Oconee

County, Georgia and checked daily. In 1998, traps were

similarly hung and checked daily within a three-year-old

loblolly pine plantation in Oglethorpe County, Georgia.

There was a concern that the interior temperature of the

cans would be elevated by being inside the pheromone trap.

To check this, measurements on temperature and humidity

were taken between 1200 and 1500 EST inside the cans on

three separate days during spring (March 11, 23, and 30,

n=12 traps per day) and summer (June 16,22, and 27, n=13

traps per day), and compared to ambient conditions just

outside the trap.

Adult Longevity-Lab Experiments

To determine if any differences found in longevity were

primarily due to temperature effects, a similar experiment was

performed in the laboratory using one spring and one

summer cohort of moths by placing them inside the same

type of paper cans and exposing them to different constant

temperatures within a temperature control unit. The moths

were exposed to constant temperatures of 5, 10, 15, 20, 25,

30, 35, and 40°C. Humidity levels were kept between 40-60

percent for all temperature treatments (n=9-41 moths per

treatment). The number of moths assigned to each treatment

was determined by their availability from the emergence cage.

It is not known whether tip moth adults feed. Many adult

moths do not feed (Boggs 1987, Han and Gatehouse 1991)

and the short life spans and activity periods of tip moths

suggest that they may not either. However, if they visit

nectaries or obtain energy from some other source, this

would clearly effect the study since moths were prevented

from obtaining any source of water or nourishment while

enclosed in the cans. Two experiments were conducted in an

attempt to test the importance of water or carbohydrates to

adult male tip moths. In Experiment 1, life span was

monitored under three treatments (n=lO moths per treatment)

in which moths were placed individually in glass vials at 20°C

with the vial opening capped with dry cotton balls (0.5 cm

diameter), cotton saturated with water, and cotton saturated

with a two molar sucrose solution. In Experiment 2, male

moths were placed individually in vials capped with dry cotton

(n=18 moths) or capped with cotton saturated with a two

molar sucrose solution (n=17), held at 10°C and checked

daily. To prevent excess moisture from adhering to and

overwhelming tip moth adults, all saturated cotton balls were

gently squeezed before being placed in a vial.

Statistical Analysis

All tests were performed using SigmaStat 2.0 (Jandel

Corporation 1995, San Rafael, CA). Average life spans from

the field and lab were compared using Kruskal-Wallis

ANOVA on ranks followed by Dunn’s test for differences in

ranked means. For comparison of internal and external trap

conditions, a paired t-test or Wilcoxon signed rank test was

used, depending on whether ANOVA assumptions were met.

Significance levels for all tests were set at n=O.O5.

RESULTS

Adult Longevity-Field Experiment

During 1997 and 1998, male moths lived significantly longer

during the first generation than the second and third

generations (1997, H=33.08, df=2, P<O.OOl; 1998, H=48.40,

df=2, P<O.OOl) (fig. 5A). During the first generation in 1997,

average (&SD) adult male life span was 7.8 (k4.0) days

(n=17) compared with the second and third generations,

which averaged 2.3 (kl.0) days (n=29) and 4.2 (lt2.1) days

(n=20), respectively. In 1998, average adult male life span

for the first generation was 12.5 (k5.8) days (n=23)

compared with the second and third generations, which

averaged 2.8 (*I .I) days (n=33) and 2.8 (+0.9) days (n=24),

respectively (fig. 5A).

Adult females from the first generation lived significantly

longer than those from the second generation in 1997

(H=19.47, df=2, P<O.OOl), while in 1998 females from the

first generation lived significantly longer than those from the

second and third generations (H=33.39, df=2, P<O.OOl) (fig.

5B). During the first generation in 1997, average (*SD) adult

female life span was 15.3 (k5.6) days (n=l7) compared with

the second and third generations, which averaged 6.4 (k2.8)

days (n=29) and 8.6 (i2.1) days (n=20), respectively. In

4 7
A

a

1997 1

1998

a

a

I

1998

a

1 2 3 1 2 3

Generation

Figure 5-Average (&SD) life span of each generation of adult R.

frustrana males (A) and females (B) in a loblolly pine plantation near

Athens, Georgia during 1997 and 1998. Within each year, means

followed by the same letter are not significantly different at a=0.05

(Dunn’s Method).

1998, average adult female life span for the first generation

was 21 .O (k8.6) days (n=23) compared with the second and

third generations, which averaged 3.4 (*I .3) days (n=33)

and 6.3 (f2.4) days (n=24), respectively.

Average &SD) daily temperature and humidity during the

1997 field experiment was 15.1 “C (rt2.8) and 57.0 percent

(*I 6.7) respectively, for first generation moths (March 18 to

April 1 I), 26.1 “C (&I 5) and 74.8 percent (~k5.7) for second

generation moths (June 19 to July 6) and 25°C (1t2.7) and

64.5 percent (f7.8) for the third generation moths (August 14

to September 7). Similarly, the average daily temperature

and humidity during the 1998 field experiment was 13.1 “C

(f4.7) and 69.5 percent (kl7.0) for the first generation

(February 28 to May 4) 25°C (k3.0) and 66.2 percent (i9.2)

for the second generation (June 4 to June 16) and 26.6”C

(*I .7) and 64.0 percent (k9.2) for the third generation (July

23 to August 6).

Internal trap temperatures were 1 .O and 05°C higher,

respectively, than ambient during spring (t= -3.54, df= 1,

P=O.O05) and summer (t= -3.18, df=12, P=O.O08), while

internal humidity was 2.8 percent lower than ambient during

spring (W = -52.0, df=ll, P=O.O42). However, these

differences were so minor that they are not thought to have

had any influence on adult longevity (table 1).

Adult Longevity-Lab Experiments

For first generation males, average life span (&SD) at 5, 10,

20, 30, 35, and 40°C treatments was 8.2 (k3.1) (n=15

males), 7.9 (f3.2) (n=22), 4.4 (k2.4) (n =29), 1.5 (k0.7)

(n=20), 1 .O (rt0.3) (n=41), and 0.7 (k0.3) (n=20) days,

respectively. The first three treatments were all significantly

different from the latter three (H=106.99, df=5, PcO.001) (fig.

6A). For second generation males, average life span (&SD)

at 5, 15, 25, 30, and 35°C treatments was 10.8 (il.9) (n=15

males), 4.3 (&I .4) (n=20), 2.4 (lt0.8) (n=lO), 2.6 (kl.1)

(n=9), and 1.6 (~tO.8) (n=lO) days, respectively. Only the first

treatment was significantly different from the latter four

treatments (H=47.93, df=4, PcO.001) (fig. 6A).

No significant differences in adult male life span were found

for any of the treatments involving dry cotton, cotton

saturated with water, or cotton saturated with a two molar

sucrose solution (Experiment 1, H=l.20, df=2, P=O.549;

Experiment 2, T=344.5, P=O.210) (fig. 6B). In Experiment I,

moths in the dry cotton treatment lived an average of 3.6

(&I .4) days, those in the wet cotton treatment lived 4.0

(i0.8) days, and those in the sugar water treatment lived 3.5

Table I-Comparison of ambient temperature (“C) and humidity with the interior

of traps used in the study. Within each season and variable measure, means

followed by the same letter are not significantly different

Spring Summer

Temperature Humidity Temperature Humiditya

Percent

Trap Interior 15.8 a 43.6 a

Ambient

(outside trap) 14.8 b 46.4 b

a Paired t-test or Wilcoxon signed rank test, a = 0.05).

31.7 a

31.2 b

Percent

52.7 a

52.2 a

4 8
4 1stGen. a 2ndGen.

T

51020303540 515253035

Temperature (C)

B Experiment

1 2

aa

/I

swwd d S W

Treatment

Figure f+-(A) Average @SD) life span of adult R. frustrana males

under different constant temperatures using moths from the first and

second generations and (B) two experiments comparing male moth

life span under different treatments (sw=sugar water, w=water only,

d=dry) and constant temperatures (Experiment 1 - 20%

Experiment 2 - 10°C).

(kO.8) days. In Experiment 2, moths in the dry cotton

treatment lived 6.7 (k3.0) days while those in the sugar

water treatment lived 7.4 (k2.0) days (fig. 2B).

DISCUSSION

During both years of the field study, it was demonstrated that

Nantucket pine tip moth adults do experience decreased

longevity during the second and third generations when

temperatures are significantly warmer. Although other

environmental or physiological factors may influence adult

longevity, temperature appears to be the most important

factor. In the laboratory experiments, humidity was kept

between 40-60 percent in the temperature control units, and

moths kept in vials capped with saturated cotton did not live

longer than those in vials capped with dry cotton under the

same constant temperatures. Although humidity was not

measured inside the vials, it was likely substantially higher in

those that were capped with saturated cotton since tiny

droplets of condensation were sometimes observed in these

vials. Furthermore, average humidity levels during the 1997

field experiment were lower in spring than in summer, while

in 1998 they were almost the same between seasons. Since

these variations were not correlated with the seasonal

change in adult longevity, it appears that humidity is not as

important as temperature in affecting adult life span.

Although the environment of the paper cans was a concern,

the small differences in temperature and humidity within the

can and the ambient conditions did not appear to have any

effect on life span.

Butler and Foster (1979) showed that adults of the pink

bollworm, Pectinophora gossypiella (Saunders)

(Lepidoptera: Gelechiidae), held at constant temperatures

lived longer than at comparable, fluctuating temperatures.

Pilon (1966) also demonstrated shorter life span under

fluctuating than constant temperatures for both sexes of the

Swain jack pine sawfly. For the Nantucket pine tip moth, life

spans in the field experiment closely matched those in the

laboratory experiment under similar average temperatures

(figs. 5 and 6). The constant temperatures used in the lab

experiments did not appear to effect this species.

Other factors that may have influenced adult longevity

include the moths inability to fly very far and expend

metabolic energy (Boggs 1987) an inability to mate, and an

inability to feed or drink. Nantucket pine tip moths mate

infrequently and produce few viable eggs when caged in the

laboratory or confined to small spaces (Cresswell and others

1971, Richmond and Thomas 1977). Partridge and Farquhar

(1981) demonstrated that sexual activity reduces the life

span of male fruit flies (Diptera: Tephritidae) while Moscardi

and others (1981) showed that unmated females of the

velvetbean caterpillar lived significantly longer than mated

females at a given temperature. Although male and female

tip moths were mixed together in half of the paper cans

placed in the field, there were no differences in the life span

of either sex compared with those that were placed in samesex cans (data not shown). The extent to which adult tip

moths feed or drink, if at all, is unknown. In their studies of

the pine beauty moth, Leather and Burnand (1987) reported

that unfed female adults had a shorter life span. Leahy and

Andow (1984) showed that diets with sugars significantly

increased oviposition period, fecundity, and adult longevity in

the European corn borer, Ostrinia nubilalis (Htibner)

(Lepidoptera: Pyralidae). Howell (1981) observed a 6-12 day

increase in adult longevity of the codling moth when

provided water, carbohydrate, or a carbohydrate-protein

solution, but no increase in mating, oviposition, or egg

viability. Kira and others (1969) reported that water was the

most important feeding requirement for adults of the

European corn borer. Our lab experiments involving sugar

solution (fig. 6B) were inconclusive. Although there were no

differences between treatments, we can only conclude that

adults do not feed or that they were not stimulated to do so

under these specific conditions. It is clear, however, that

addition of food and water did not affect the life span of adult

moths in captivity. There are a number of species of moths

that do not feed as adults (Boggs 1987, Han and Gatehouse

1991). Indeed, in many species of Lepidoptera, the maximal

number of eggs an individual can lay is proportional to the

amount of stored nutrient reserves acquired during larval

feeding (Engelmann 1970). In other species, carbohydrates

obtained during adult feeding are either used immediately in

oogenesis or stored as glycogen in the fat body and used

after hydrolysis. Glycogen seems to be involved in the

maintenance of body weight and oocyte production

(Kozhantshikov 1938, Chapman 1982).

There is a pronounced difference in adult longevity between

spring and summer. This helps to explain why summer trap

catches of the Nantucket pine tip moth often drop

precipitously from spring to summer despite constant or

increasing populations. This should be taken into account

when using traps to monitor moths and making population

estimates based on trap catch.

4 9
ESTIMATING NANTUCKET PINE TIP MOTH

POPULATIONS FROM TRAP CATCH - METHODS

This study was conducted over a 4-yr period from 1997-2000.

Ten study sites of two or three-yr-old loblolly pine (Pinus

taeda L.) plantations were used in the Georgia Piedmont

within Clarke, Morgan, and Oglethorpe counties, where there

are three tip moth generations per year. Plantation size varied

from 3 to 20 ha and tree density varied from 1.8 x 3 m (1,794

trees / ha) to 1.8 x 3.7 m (1,495 trees / ha).

Pheromone Trap Catch

A 2 ha rectangular plot was established within each

plantation. Six Pherocon lC* wing traps baited with red

rubber septa loaded with synthetic R. frusfrana pheromone

(Trece Inc., Salinas, CA) were placed on each plot, one in

each corner and one midway along each of the longer two

sides. Traps were at least 30 m from the plantation edge and

more than 30 m apart. Baits were replaced weekly to insure

high efficacy. The number of males trapped was recorded,

and insects were removed or trap bottoms replaced every 3-

5 days from February to October during each year of the

study.

Population Density and Damage Estimation

Prior to the onset of adult emergence for each generation,

40 trees were randomly selected within each plot. Gargiullo

and others (1983) showed that this sample size is adequate

for making estimates of per tree populations for all tip moth

life stages using a two-stage cluster sampling method. For

this procedure, each tree was divided into two strata, and

the total number of shoots per stratum recorded. Three

shoots from each stratum were randomly selected, clipped,

and collected in paper bags. A shoot was defined as being

at least 5 cm long and terminating in a bud. In tree strata

containing more than 20 shoots, shoots were clustered

together into equivalent sampling units so that three of these

clusters represented a significant proportion (1 O-20 percent)

of the total number of shoots within each stratum. This

sampling procedure was designed to be quick, efficient, and

robust to the extensive variation found in tree size and form

within a plantation.

Clipped shoots were dissected and the number of larvae and

pupae and their condition (apparently healthy, parasitized,

diseased, or dead) was recorded. Using the methods of

Gargiullo and others (1983) the number of viable moths per

tree was estimated for each generation. It was assumed that

all apparently healthy larvae and pupae would persist in this

condition until they emerged as adults. This density estimate

was compared with the average number of moths

subsequently caught during the entire trapping period within

each generation and each site. Dead or nonviable life stages

were not included in the density estimate since they would

not contribute to the adult population.

Sampling was timed so that the maximum number of pupae

would be collected before adult emergence began for each

generation. This ic not difficult to do for the spring

generation, when all overwintering moths are simultaneously

in the pupal stage. Unparasitized pupae stand a good

chance of surviving to adulthood since most parasitism

occurs during the earlier stages of tip moth development

(Gargiullo and Berisford 1983). Therefore, viable pupae

should provide a reasonable estimate of adult population

density to relate to adult trap catch. For later generations,

however, development is somewhat staggered, with several

developmental stages often present at the same time.

Therefore, it was not possible to obtain samples for these

later generations prior to adult emergence that did not

include larvae.

In addition to estimates of population density, whole tree

damage estimates were also obtained from each site prior to

each adult emergence period. For each of the 40 randomly

sampled trees within a plot, the total number of shoots per

tree and the total number of damaged shoots per tree

(indicated by a visible pitch mass near or on the bud and

dead or dying needles) were counted. In this case, a shoot

was defined as being at least 2.5 cm long and terminating in

a bud. No clustering of shoots was done, as above, for these

estimates.

Statistical Analysis

Relationships between population density, host damage and

trap catch were described with linear or non-linear

regression models using Sigmaplot 4.01 (SPSS Inc. 1997,

Chicago, IL). Scatter plots were examined prior to regression

to determine the most appropriate model, which was

evaluated by looking at the r2 value, heteroscedasticity and

whether the model was likely to be robust to other similar

data sets (Sokal and Rohlf 1995).

RESULTS AND DISCUSSION

During 1997, 1999, and 2000, pheromone trap catches

generally decreased dramatically from the first adult

generation through subsequent generations despite

considerable increases in population density, mostly

between the over-wintering and first generation broods (fig.

IA& fig. 3A,C; fig. 4A,B). This pattern was not as evident in

1998, however, when spring populations were considerably

lower than the two subsequent generations and populations

were low overall (fig. 2AC). In one case, the second trap

catch peak was slightly greater than the first, spring peak

(fig. 2A), but there was an almost four-fold population

increase during this period. In general, the magnitude of the

second and third adult emergence peaks relative to

population density were comparable to each other but not

with that of the first emergence peak. For example, the mean

(*SE) ratio of total trap catch to population density (number

of moths per tree) was 707 (1t.216) for the first adult

emergence peak, 114 (533) for the second peak, and 97

(il3) for the third peak.

At most sites in all years, trap catches show a small but

distinct fourth emergence peak at Julian dates 240-260

(figs. l-4). Although only three generations were reported in

this part of Georgia (Fettig and others 2000a), a small

proportion of the third generation population may not

diapause, and may emerge in the fall under favorable

climatic conditions. Larvae from these adults apparently do

not survive so late in the season (Kudon and others 1988).

The late catches were combined with the third generation

catches for convenience because it would be very difficult to

5 0
tell which moths, if any, represented a partial fourth

generation.

respectively, for the first generation (fig. 7A, y=2815.277

[SE=339.584]x)/(2.014 [SE=0.790]+x, pcO.001); figure 76,

y= (4660.129 [SE=1698.476]x)/(61.730 [SE=40.660]+~,

A strong positive relationship was found between total trap p<O.OOl)), and a moderately strong positive relationship

catch and tip moth population density and damage, between these parameters for the second (fig. 7C,

ti = 0.82

0 4 8 1 2 18

# Moths /tree - Overwintering

brood generation

0 2 0 40 60 8 0 100

% Shoot damage - Overwintering

brood generation

D l l

3 = 0.67

2 0 40 60 8 0

# Moths I tree

1 st brood generation

% Shoot damage

1st brood generation

100

ol-

/ .

l .

490.706x

.

í =19.986 + x

rz = 0.41

4

0 1 2 3 4 6 6 7 10 2 0 20 40 60 6 0 7 0 60

# Moths I tree % Shoot damage

2nd brood generation 2nd brood generation

621.868x

‘= 3.227+x

fl= 0.67

Figure 7-Regression analyses modeling the relationship between A) R. frusfrana overwintering

brood population density and total trap catch during the first adult generation, B) average percent

shoot infestation of the overwintering brood and total trap catch during the first adult generation, C)

R. frusfrana population density of the first generation brood and total trap catch during the second

adult generation, D) average percent shoot infestation of the first generation brood and total trap

catch during the second adult generation, E) R. frusfrana population density of the second

generation brood and total trap catch during the third adult generation, and F) average percent

shoot infestation of the second generation brood and total trap catch during the third adult

generation. A hyperbola was used for each model. Normality and homoscedasticity were present in

all models.

5 1
y=(747.059 [SE=170.178]~)/(2.823 [SE=1.998]+x, p=O.O04);

Figure 70, y=(893.307 [SE=300.707]x)/(27.958

[SE=21.535]+x, p=O.O04)) and third (fig. 7E, y= (621.868

[SE=206.470]~)/(3.227 [SE=2,155]+x, p=O.O04); Figure 7F,

y=(490.706 [SE =186.6251x)/( 19.986 [SE=1 8.6921+x,

p=O.O45)) generations. The relationship between trap catch

and tip moth density (average number of moths per tree)

was best fit by a hyperbola, which explained 89, 66, and 67

percent of the variation for the first, second, and third

generation models, respectively (fig. 7A, C, E). Similarly, the

relationship between trap catch and damage (average

percent of shoots infested per tree) was best fit by a

hyperbola, which explained 82, 67, and 41 percent of the

variation for the first, second, and third generation models,

respectively (fig. 78, D, F). The hyperbolic pattern of these

data suggest that trap saturation may occur at very high

densities. Ramaswamy and Garde (1982) reported that

Pherocon ICY’ trap efficiency decreased with increasing

catch of male spruce budworms (Choristoneura fumiferana)

due to a reduction of sticky surface area within the trap.

Increased competition from calling females may also cause

trap catch to level off at high densities (Knipling 1979,

Unnithan and Saxena 1991). However, trap saturation was

not apparent within the range of densities seen in this study.

The fate of the larval instars sampled is much less certain

than that of pupae due to a greater potential for mortality

factors such as parasitism and resinosis (Gargiullo and

Berisford 1983). Therefore, population density estimates of

viable moths from samples collected during the summer

generations, which included larvae and pupae, should be

less accurate than the estimates for the spring generation.

Hence, it should become more difficult to relate population

density to trap catch during the summer generations.

Density estimates were not better correlated with trap catch

than damaged shoots, except during the third generation.

This was unexpected because damaged shoots often

contain dead or parasitized moths that will not contribute to

trap catch tallies. Therefore, shoot damage as a population

estimate was originally thought to be less precise. Percent

shoot damage can sometimes be poorly correlated with trap

catch (fig. 7F); two outlying points cause this regression to

be substantially poorer than the associated regression using

tip moth density (fig. 7E). One of these outliers had 89

percent tip moth mortality within the damaged shoots during

the third generation (data not shown). This produced an

overestimate of tip moth populations. When shoots are

sampled and dissected, however, the number of non-viable

tip moths can be determined and a more realistic

association with trap catch can be made. The other outlier

was caused by the opposite phenomenon, in which trap

catch produced an underestimate of the population. It only

takes one or two such outliers to substantially weaken the

strength of a regression model. We could not determine

whether the poorer correlation in the third generation is

biologically significant or simply happenstance.

Using damage as an indicator of trap catch rather than

density does seem feasible given the outcome of the

regression models from the first two generations.

Furthermore, damage estimates are significantly less labor

intensive, can be done quickly in the field, and require much

less expertise than randomly sampling shoots, dissecting

them in a laboratory, and determining the extent of tip moth

parasitism and mortality. Therefore, future studies should

associate trap catch with percent shoot damage per tree,

which is more easily obtained and meaningful to forest

managers.

Although trap catch appears to be closely linked with

population density and damage within generations (fig. 7)

the predictive value of these models is limited. It is more

desirable to predict what tip moth populations will be in the

next generation based on trap catch during the current

generation. Total trap catch during the first adult generation

is a strong predictor of tip moth density (fig. 8A, y=O.O06

[SE=O.OOl]x - 2.175[SE=1.512], r*=0.83, p<O.OOl) and

damage (fig. 8B, y=O.O24 [SE=O.O03]x - 2.022 [SE=5.114],

r*=0.87, p-=0.001) during the next generation using a linear

model. However, total trap catch during the second adult

generation was a poor predictor of density (fig. 8C, y =0.004

[SE=O.O02]x + 1.299 [SE=1.102], r*=O.24, p=O.146) and

damage (fig. 80, y=O.O47 [SE=O.O2l]x + 10.270 [SE=9.463],

r2=0.38, p=O.O59) during the subsequent generation. In both

cases, however, trap catch predicted damage more

accurately than it predicted density. No attempt was made to

use the third adult generation trap catch to predict

subsequent damage or density of the overwintering brood

(next years first adult generation). The extended and

unpredictable overwintering period usually results in greater

fluctuations in tip moth density, tip moth damage, and

mortality factors compared with fluctuations within the same

year (data not shown), making it inherently more difficult to

predict what will happen during the winter. Furthermore, the

sites in this study for which measurements were carried over

a second or third year (Arnoldsville, Maxeys, Lexingtion)

show a very poor correlation between third adult generation

trap catch and subsequent density (r = 0.36) and damage (r

= 0.33) of the overwintering brood.

Third generation population density and damage is

inherently difficult to predict using traps. This is not

surprising given that spray-timing models are also

significantly less accurate during the third generation. Fettig

and others (2000b) reported control as low as 55.5 percent

for the third generation when control for the first and second

generations averaged 90.4 percent and 77.6 percent,

respectively. This most likely occurs because adult

emergence during the last generation is much more

protracted than earlier generations (figs. l-4) and there is a

progressive decrease in the synchrony of life stages

throughout the year. Hence, avoiding chemical control of the

third generation brood has been proposed (Fettig and others

2000b).

Trap catch tallies used in the regression models (fig. 8) were

totals for the entire adult emergence period. This is not

entirely adequate if trap catch is to be used to predict

numbers or damage for subsequent generations because in

order to count total moths for the entire emergence period,

one must pass the optimum spray date for the next

generation. This problem can be overcome if one assumes

that a certain percentage of the total moths to emerge will

be caught prior to the spray date. Spray dates for many

areas of the southeast can be determined following the

5 2
y-0.006x-2.175

If=0.83 .

Total trap catch

Adult generation 1

y=1.300 *0.004x .

8-0.24

Total trap catch

Adult generatlon 2

y=O.O24x- 2.022

8=0.87 .

.~

0 600 1000 1500 2000 2500

Total trap catch

Adult generation 1

y= 10.270+0.047x .

13'0.38

0 100 200 300 400 600 600 700

Total trap catch

Aduitgeneratbn2

Figure &Regression analyses modeling the relationship between A) total trap catch during the first

adult generation and R. fmstrana population density during the first generation brood, B) total trap

catch during the first adult generation and average percent shoot infestation during the second

generation brood, C) total trap catch during the second adult generation and R. frustrana population

density during the second generation brood, and D) total trap catch during the second adult

generation and average percent shoot infestation during the second generation brood.

methods of Fettig and others (2000a) and are based on the

accumulation of degree-days, which relate to the , developmental rates of R. frustrana following oviposition. In

the current study, the mean &SD) percentage of total moths

caught prior to the spray date was 65.3 percent (~1~14.6) for

the first adult generation, 85.1 percent (f6.7) for the second

adult generation, and 47.9 percent (k23.1) for the third adult

generation. During three of the four years of this study, these

percentages were fairly consistent (data not shown).

Variation can be considerable, however, since trap catches

are strongly influenced by temperature and the spray date is

determined through the accumulation of degree-days (Fettig

and others 2000b). Nevertheless, application of these

percentages to the x-axis of figure 8 will provide predictive

trap catch numbers prior to the spray date. For example,

figure 88 demonstrates that catching 1836 moths (65.3

percent of 2812) prior to the predicted optimum spray date

during the first adult generation would result in 80 percent

shoot damage per tree during the subsequent generation.

Similarly, catching 539 moths (65.3 percent of 825) prior to

the spray date during the first adult generation would result

in approximately 20 percent shoot damage per tree during

the subsequent generation. In the former case, chemical

control would probably be warranted, while in the latter case

it may not be. Although a damage threshold for R. frusfrana

has not been established, recent studies suggest that

damage levels of less than 40 percent infested shoots may

cause significant growth loss (Nowak and Berisford 2000,

Fettig and others (2000b), Asaro and Berisford, unpublished

data). Therefore, Figure 88 suggests that trap catches above

1,000 moths (approximately 65 percent of 1500) prior to the

spray date would warrant chemical control to avoid

significant volume reductions.

These models should be used with caution since they have

not been validated in other areas. Trap catch numbers may

be substantially different in other regions since they are

strongly influenced by temperature. Consideration of tree

5 3
age or size may be important, particularly in areas where

pines grow rapidly. For example, x percent shoot damage on

a tree that is 1 m tall will harbor a much smaller tip moth

population than x percent shoot damage on a tree that is 3

m tall, assuming parasitism rates are similar. Therefore, if

tree age or height is not taken into account, very inaccurate

predictions of tip moth infestation based on trap catch may

result. In the current study, no attempts were made to stratify

plantations by age, size, tree density or tree height (although

the range of these parameters was limited) because of the

small number of sites and a desire for these prediction

models to be widely applicable to any and all site conditions

within a region. These specific models are not necessarily

appropriate for every region and circumstance, however, and

validation will be a necessary next step before their

widespread use is adopted.

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55
NANTUCKET PINE TIP MOTH, RHYACIOMA FRUSTRANA,

LURES AND TRAPS: WHAT IS THE OPTIMUM COMBINATION?

Gary L. DeBarr, J. Wayne Brewer, R. Scott Cameron and C. Wayne Berisfordl

Abstractdheromone traps are used to monitor flight activity of male Nantucket pine tip moths, Rhyacionia frustrana

(Comstock), to initialize spray timing models, determine activity periods, or detect population trends. However, a standardized trapping procedure has not been developed. The relative efficacies of six types of lures and eight commercial pheromone traps were compared in field tests in Alabama, Georgia, South Carolina, and Virginia. Additional factors, including trap

color, lure longevity and loading rates and ratios were also tested. These tests demonstrate that lures and/ or traps have a

pronounced effect on male moth catches. The Pherocon 1Cwing trap was the most effective. White traps were slightly

better than colored traps. Pherocon 1 C? wing traps baited with commercial Scent@, Ecogen@ or Tr&@ lures caught the

greatest numbers of moths.

INTRODUCTION

Female NPTM Sex Pheromones and Male

Response

Larvae of the Nantucket pine tip moth (NPTM), Rhyacionia

frustrana (Comstock), bore into and kill the shoots of loblolly

pine, Pir~us faeda L.(Yates 1960). NPTM mate shortly after

they emerge from infested shoots. Female moths produce

small quantities of sex pheromones that attract conspecific

males for mating (Manley and Farrier 1969). Females exhibit

crepuscular behavior and begin emitting their pheromones

(“calling”) at dusk (Berisford 1974; Berisford and others

1979). Their calling period lasts for two hours or less each

day. It ends just before a sympatric species, the pitch pine tip

moth, R. rigkfana (Fernald), begins its calling period at about

1 hr after the onset of darkness (Berisford 1988). In the

spring, peak male flight activity and the highest NPTM

catches in pheromone-baited traps occur just before dark

(Berisford and Brady 1972). NPTM fly when temperatures

equal or exceed 10 EC (50 EF) (Webb and Berisford 1978).

In the summer, when average temperatures are higher, male

flight is later in the evening and less intense.

Berisford and Brady (1972) noted that catches of NPTM

during the emergence of the overwintering generation in

March and April were higher than those of later generations.

They speculated that overwintering females might produce

and release more pheromone than summer females.

Alternatively, male response may be stronger in the spring,

than during the summer, which would provide an advantage

by insuring mating when NPTM populations are low. They

also suggested that male catches in traps may decrease

when large numbers of feral females are present to compete

with the traps. Recent investigations have shown that

catches in traps baited with synthetic pheromone lures are

also lower during later tip moth generations even though

populations are high (Asaro and Berisford 2001 a).

The Pheromones

NPTM females produce a two-component sex pheromone

(Berisford and Brady 1973) and their pheromone glands

contain only about 20 nanograms (ng) of attractive

components. Hill and others (1981) identified a straightchain 12 carbon monoene acetate, (E)- 9-dodecen-I-yl

acetate, (E9-12:OAc), as the major pheromone component

in female gland extracts and a straight-chain 12 carbon

diene acetate, (f,E)-9,11-dodecadien-I-yl acetate,

(E9,Ell-12:OAc), as a minor component. The components,

f9-12:OAc and E9,Ell-12:OAc occur in a 96:4 ratio in the

female glands. Field tests in the Georgia Piedmont during

first and second NPTM generations demonstrated that a

synthetic mixture of these two compounds is as effective in

attracting NPTM males, as conspecific females. Three other

compounds, dodecan-l-01, E-9-dodecenol (E9-12-OH) and

dodecan-I-yl acetate, were present in the female glands

but their role, if any, in pheromonal communication by

NPTM remains unknown.

NPTM Lures and Traps

Tests conducted in the Georgia Piedmont during the first and

second generations of NPTM show that 1 .O mg of E9-

12:OAc plus 0.025-0.050 mg of E9,Ell-12:OAc dispensed

on a red rubber septum was an effective lure for NPTM (Hill

and others 1981). Based upon this research, several NPTM

lures are now available from commercial sources. These

lures contain synthetic E9-12:OAc and E9,Ell-12:OAc

impregnated into rubber septa, plastic laminates, or

dispensed from hollow glass fibers. Since the original work

of Hill and others (1981), no additional field tests have been

conducted to compare the performance of various lures,

’ DeBarr, Research Entomologist (Retired), Southern Research Station, USDA Forest Service, 320 Green Street, Athens GA 30602-2044;

Brewer, Professor of Entomology, Department of Entomology, Auburn University, Auburn, AL 36849; Cameron, Forest Health Manager,

International Paper Company, PO Box 1391, Savannah, GA 31402; and Berisford, Professor of Entomology, Department of Entomology,

University of Georgia, 413 Biological Science Bldg., Athens, GA 30622-2603.

Citation for proceedings: Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old problems, new research.

Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep.

SRS-51. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 68 p.

5 6
longevity of the lures, and optimum dosages and ratios the

two NPTM pheromone components in other parts of the

range of NPTM or for later generations. Two types of

commercially available sticky traps, delta-style and wingstyle, are currently used for NPTM. Tests have not been

conducted to compare the efficiency of these two traps or

others types of commercially available traps.

The efficiency of lures for NPTM depends on the amount

and ratios of the two synthetic pheromones released. Lures

that release too little pheromone will not attract moths; those

that release too much may inhibit them. Research on lures

for the coneworms, Dioryctria spp., clearly showed that

catches of male moths in pheromone-baited traps are

related to lure release rates (Meyer and others 1982, 1986).

Lures that release the wrong ratios of the two pheromone

components may also be unattractive (Hill and others 1981).

Good lures can be more attractive than females. The best

lures for the European pine shoot moth, R. buoliana

(Schiffermuller), which uses the same major pheromone

component as NPTM, attract 20 times more males than a

single female moth (Smith and others 1974, Daterman

1974).

The amount of pheromone released per female NPTM and

whether the rate of release and ratio of the two

pheromones is constant for each generation is unknown.

Females in later generations may be able to maintain the

96:4 natural blend, while compensating for higher ambient

field temperatures by releasing more pheromone than at

low temperatures. We also do not know if the quantities and

natural blend of two components released by NPTM

females in Piedmont Georgia are the same in other parts of

its range.

Also unknown is how accurately the synthetic pheromones

in NPTM lures emulate the natural blend released by

females. Formulating NPTM lures is complicated because

the attractive blend requires two components, and the minor

component is an unstable diene. Factors that affect the rate

of loss and stability of synthetic pheromones from NPTM

lures include chemical structure of the pheromone, ambient

field temperatures, rate of air movement over the lure, lure

type, and dosage. The unique volatility of each component

of Lepidoptera pheromones is determined by the length of

the carbon chain, the number and position of double bonds,

and the functional group. E9-12:OAc and E9,Ell-12:OAc

each have their own vapor pressure constants, which

determine their evaporation rates from NPTM lures. Local

field conditions, primarily the seasonal and diurnal

fluctuations in ambient temperatures, greatly affect the

pheromone loss rates and half-life of NPTM lures at any

given field site and for each NPTM generation. For example,

over an 8 day period polyvinyl chloride (PVC) baits lose 18

percent of their E9-12:OAc with daily maximum

temperatures of 20-23 EC (68-74 EF), and 37 percent with

daily maximum temperatures of 27-29 EC (80-85EF)

(Daterman 1974). On hot summer days NPTM lures emit

more pheromone than on cooler spring or fall days. Unless

the half-life for E9,Ell-12:OAc and E9-12:OAc are the same

for a lure, the ratio of two components may change,

peducing its attractiveness.

Natural or butyl rubber septa (laboratory stoppers), PVC

dispensers, and laminated dispensers, such as Hercon

Luretapes@, all emit pheromones by a first-order process,

where the rate of evaporation is directly proportional to the

amount of pheromone remaining in the lure (Butler and

McDonough 1981). Natural red rubber septa are commonly

used to prepare lures with Lepidoptera sex pheromones for

monitoring traps. Natural red rubber septa have a large

loading capacity (> 75 mg) and are composed of a crosslinked polymer that releases most straight-chain

pheromones at moderate to very slow rates providing lures

with a long half-life (Butler and McDonough 1981). Septa are

inexpensive and can be easily loaded without highly

specialized equipment. The major component of the NPTM

pheromone, E9-12:OAc, has a 12-carbon chain and a halflife of 38 days on red natural rubber septa (Butler and

McDonough 1981). The half-life for E9-12:OAc is almost 3

times greater on natural red rubber septa, as on PVC baits

(Daterman 1974). We are unaware of any published half-life

data for the minor component of the NPTM pheromone,

E9,Ell-12:OAc, on septa or PVC lures. If the half-life for

E9,Ell-12:OAc on a lure is the same as for f9-12:OAc the

ratio of these two components released from the lure will

remain constant through time. Otherwise, the ratio will

change.

The dosage of 1 mg per NPTM lure (Hill and others 1981) is

relatively high compared to many other forest Lepidoptera. A

plastic laminate lure for gypsy moth, Lymantria dispar (L.),

has 0.5 mg of pheromone (Leonhardt and others 1992) a

red septum lure for the webbing coneworm, D. disclusa, has

0.1 mg of pheromone (Meyer and others 1982) and a

septum lure for the spruce seed moth, Cydia strobilela (L.)

has only 0.0003-0.003 mg (Grant and others 1989). Lures of

PVC (or other non-cross-linked polymer) are useful for

insects which respond to relatively high amounts of

pheromone because the desired release rate can be

obtained with a lower dosage per lure (Butler and

McDonough 1981). The optimum release rate of E9-12:OAc

from PVC lures was 5-56 ng/min for R. buoliana (Daterman

1974) but the optimum release rate for NPTM is unknown.

Release rates of 30 rig/h are attractive to gypsy moths and

capture rates in traps baited with PVC-twine lures remain

uniform throughout a period of 16 weeks (Leonhardt and

others 1992).

Laminated plastic lures, such as Hercon Luretapes@, consist

of thin layers of vinyl or other polymers, with synthetic

pheromone incorporated into the inner layer at 1.5 to 2.0

percent by weight (Beroza and others 1974). Laminated

dispensers also follow first-order loss (McDonough 1978)

but we are unaware of published data for the half-life of E9-

12:OAc or E9,Ell-12:OAc. In contrast, several commercial

lures, such as Consept@ membrane lures, Phero Tech@

bubble-cap lures, and the Sentry@ capillary tube or hollowfiber lures approximate a zero-order pheromone release.

Emission rate for zero-order lures is constant and

independent of the concentration of the liquid pheromone

(McDonough 1978) but relatively large amounts of neat

pheromone are required for these dispensers, which can

increase their cost.

5 7
Trap catches and degree-day models

NPTM males are present at the start of each generation,

before the first females emerge and begin to lay eggs

(Berisford and Brady 1972). Sticky traps baited with

synthetic pheromone lures are currently deployed in

intensively managed plantations of loblolly pines. Pest

managers check these traps frequently to determine the

beginning of each new generation. When the trap catch

equals or exceeds an average of one male NPTM per trap

they begin accumulating degree-days for the NPTM

temperature/development models (Gargiullo and others

1984; Pickering and others 1989). These models predict the

optimum dates for spraying plantations to control NPTM

(Gargiullo and others 1983, 1985; Berisford and others 1984:

Kudon and others 1988). A model for the coastal plain is

also available (Gargiullo and others 1985).

In practice, traps baited with lures containing synthetic

NPTM pheromones generally catch high numbers of male

moths in infested plantations during the first and second

generations, but lower and more variable catches can occur

for later generations. This poor response is particularly

evident in the coastal plain during the summer months

(Gargiullo and others 1985) even when abundant shoot

attacks suggest that NPTM populations are high (Asaro and

Berisford 2001 a). Male flight periods are also less distinct

and often overlap for generations 3 and 4 (Gargiullo and

others 1985). An alternative technique is to catch first

generation NPTM males in traps, then continue

accumulating degree days throughout the entire season for

predicting the optimum spray dates for all four generations

(Gargiullo and others 1985). Unfortunately, these predictions

are not as accurate as those using models based upon the

onset of each generation and in turn NPTM control is not as

good. A method which uses only long-term average

temperatures for timing control is also available for seven

southern states (Fettig and others 2000).

High efficiency lures and traps are essential for obtaining an

accurate date to begin accumulating degree-days for the

NPTM models. A standard trap is also needed in order to

use pheromone-baited traps for estimating relative

population densities. Finally, the successful use of synthetic

sex pheromones for NPTM control strategies, such as

mating disruption, depend upon a clear understanding of

male moth response to synthetic pheromones. The objective

of our studies was to investigate some of the factors

affecting catches of male NPTM in sticky traps baited with

synthetic pheromones and determine promising areas for

further research.

MATERIALS AND METHODS

Preparation of Custom Red and Gray Lures

Custom red and gray lures were prepared at the Forestry

Sciences Laboratory, Athens, GA. The major component of

the NPTM pheromone, f9-12:OAc (97.9 percent purity) was

purchased from Bedoukin Research Inc., Danbury, CT. The

minor component, E9,Ell-12:OAc (88.4 percent purity), was

purchased from Chemteck B. V., Amsterdam, The

Netherlands. Purity was verified using a Hewlett-Packard

GC-MS. The neat synthetic pheromones were stored at - 40

EC until used to formulate pheromone solutions for the

custom red and gray septa lures. Red, natural rubber sleevetype septa, 1.9 by 1 cm (Arthur H. Thomas, Philadelphia, PA)

and gray, sleeve-type septa, 1.9 by 1 cm, composed of a

halo-butyl isoprene blend elastomer (West Company,

Phoenixville, PA) were labeled with a treatment code using a

black permanent marking pen.

Stock solutions containing E9-12:OAc and E9,El l-l 2:OAc

in nanograde dichloromethane were prepared and

dispensed in 0.1 ml aliquots into the well of each septum.

Two additional 0.1 ml aliquots of the solvent were added to

each well to insure that any residual pheromone was

impregnated into the septa (Brown and McDonough 1986).

Loaded septa were allowed to age for 48 hours in a

laboratory fume hood (20-24 EC) and then they were

wrapped in aluminum foil, placed in labeled glass screw-top

bottles, and stored at -40 EC. The first batch of custom gray

and red septa lures were prepared on 5 February 1997; a

second batch of lures were loaded on 8 May 1997 because

we decided to include more tests sites than originally

planned. Custom red septa lures from batch 2 were used in

tests 6, 9, 11, and 12; custom gray lures from batch 2 were

used in tests 6, 11, and 12.

Experimental Design

Each field test was installed in a 2- or 3-year-old loblolly pine

plantation with approximately 700 trees per acre. Rows of

trees served as a block in a randomized complete block

design. Trap positions equal to the number of treatments in

the test were established by marking every fifth tree within

the row with colored flagging. One row of trees without traps

was left between each row of frees with traps. Within each

block (row), treatments were randomly assigned to each

position. The treatments were rerandomized each time the

traps were checked by moving the traps to new positions.

Each field test had 5 replicates per treatment, except for the

trap design and color tests, which had 6 replicates per

treatment.

Trapping Procedure

At each trap position within a test site, a single trap was

hung in the tree, near the top, and at approximately the

same height (1.0-I .4 m) and cardinal direction relative to

the tree stem. The total number of traps used in each test

equaled the number of treatments times the number of

replicates (blocks). Lures were stored in a freezer and

transported to the field in a cooler with ice. Disposable

rubber gloves were worn while handling the lures and were

changed for each kind of lure. A 1 cm hole was punched in

the top of each of the Pherocon 1 C traps@, Pherocon CP

traps@, Pherocon II traps@, and the Trece Delta traps@ so that

a paper clip could be used to suspended a lure from the trap

top and prevent it from contacting the sticky trap bottom.

New traps and lures were deployed for each test. Traps were

checked twice a week at 3-4 day intervals. NPTM caught in

the traps were removed and the numbers were recorded on

each day the traps were checked.

Commercial and custom NPTM lure tests

Twelve field tests were conducted during 1997-98 to

compare commercial and custom NPTM lures. Commercial

lures were purchased from Gempler’s Inc., Mt. Horeb, WI

58 ’
and Great Lakes IPM, Vestaburg, MI; each custom red or

gray septum lure was loaded with 1 mg of synthetic E9-

12:OAc and f9,Ell-12:OAc (2O:l) as described above. Five

to seven of the following treatments were included in each

test: 1) Hercon Luretapes@ (Hercon Environmental Corp.,

Emigsville, PA), 2) Scent@ hollow fiber lures, 3) T&e Red

Septa@ NPTM lures (Trece Incorporated, Salinas, CA), 4)

Ecogen@ Red septa lures (Ecogen Inc., Columbia, MD), 5)

Custom Red septa, 6) Custom Gray septa, and 7) Control

(unbaited trap). Pherocon 1 C@ wing traps (with white plastic

top) were used for all treatments. Tests were conducted at

sites in Bulloch County, GA; Madison County, GA: Oconee

County, GA; Oglethorpe County, GA, Bulloch County, AL,

Macon County, AL, Beaufort County, SC; and Southhampton

County, VA.

Trap Design Tests

Two field tests were conducted to compare catches of male

NPTM in eight commercial traps (fig. 1). Traps were

purchased from Gempler’s Inc., Mt. Horeb, WI or Great

Lakes IPM, Vestaburg, Ml. Eight treatments with the

following traps were tested: 1) Pherocon 1 C@ wing trap (with

white plastic top), 2) Pherocon 1 C@ wing trap (with brown

plastic top), 3) Pherocon CP@ wing trap (white), 4) Trece

Deltaa trap (orange), 5) Trece Delta@ trap (green), 6) Trece

Pherocon II@ trap (white), 7) Pherocon Bucket@ trap (yellow/

white), and 8) Pherocon Bucket@ trap (green). Assembly of

all traps followed the printed instructions included with the

traps. Cattle ear tags containing dichlorvos (DDVP)

insecticide (Y-Tex Corporation, Cody, WY) were cut in thirds

and one piece was placed in the bottom of each bucket trap

to kill the moths caught in the traps. T&e red rubber septa

were used as lures in all of the traps. The tests were

conducted from 20 May - 29 June, 1998 in Oglethorpe

County, GA and from 15 May - 9 June, 1998 in Bullock

County, AL during the emergence of the second generation

of NPTM.

Trap Color Tests

Two field tests were conducted to compare catches of male

NPTM in Pherocon 1 C@ wing traps painted with eight

different colors. Treatments included: 1) Red, 2) Yellow, 3)

Green, 4) Orange, 5) White, 6) Black, 7) Blue, 8) Gray, and

9) Unpainted (Control). All colors except orange were

ColorPlace@ fast-drying spray paint (WalMart, Bentonville,

AK). Orange paint was not available in that brand so Krylona

interior/exterior spray paint (Sherwin-Williams, Cleveland,

OH) was used. The traps were painted one week prior to the

tests and left outdoors to allow the paint vapors to dissipate.

The first test was conducted from 26 June to 24 July, 1998 in

Bullock County, AL. during the emergence of the second

NPTM generation. The second test was conducted at the

same site from 7 August - 4 September, 1998 during the

emergence of the third NPTM generation.

Lure Longevity Test

One field test was conducted to compare the effects of lure

longevity on catches of male NPTM in Pherocon 1 C@ wing

traps. There were three treatments: 1) Trece Red Septa”

NPTM lures replaced weekly, 2) Trece Red Septa@ NPTM

lures unchanged, 3) unbaited (Control). The test was

conducted in Macon County, AL from 11 July to 8 August,

1997.

Optimum Dosage and Ratio of E9-12:OAc : 13,Ell12:OAc Tests

A field test was conducted to compare the effects of several

dosages of f9-12:OAc : .E9,Ell-12:OAc on catches of male

NPTM in Pherocon 1 C@ wing traps. Custom Red rubber

septa lures were loaded with synthetic NPTM pheromones

for six treatments with dosages of .E9-12:OAc : f9,Ell12:OAc (2O:l) per lure: 1) 2 mg, 2) 1 mg, 3) 0.5 mg, 4) 0.25

mg, 5) 0.125 mg, and 6) unbaited trap (Control). The test

was conducted in Oconee County, GA 20 March to 5 May,

1997.

A second test was conducted to compare the effects of E9-

12:OAc : f9,Ell-12:OAc ratios on catches of male NPTM in

Pherocon 1 C@ wing traps. Custom Red rubber septa lures

were loaded with 1 mg of synthetic NPTM pheromones for

six treatments with ratios of E9-12:OAc : f9,Ell-12:OAc: 1)

51, 2) lO:l, 3) 20:1, 4) 40:1, 5) 80:1, and 6) unbaited trap

(Control). The test was conducted in Oconee, GA 20 March

to 5 May, 1997.

Data analyses

Treatment means and standard errors (& SE) were

calculated for each test. Trap catches of male NPTM were

transformed by log, (x + 1) to meet the assumptions of

analysis of variance (ANOVA) and analyzed using PROC

GLM for randomized complete block designs, followed by the

Tukey test at ’ = 0.05 (SAS Institute 1990).

RESULTS

There were significant differences (F44,248 = 5.59, P = 0.0001)

in catches of NPTM among rows (blocks) within each of the

12 Lure tests. In all of our field tests, traps in the two outer

rows of trees generally caught more moths than traps placed

in trees located in interior rows.

Commercial and custom NPTM lure tests

There were significant differences in trap catches among

traps baited with the various lures treatments in 10 of our 12

Lure tests (fig. 2-5): Test # 1 F = 3.48, P = 0.0315; Test # 2 F

= 1.26, P= 0.3213; Test# 3 F = 4.68, P = 0.0108; Test#4 F

= 4.89, P= 0.0090; Test# 5 F= 1.82, P = 0.1547; Test# 6 F

= 12.96, P= 0.0001; Test#7 F= 5.59, P= 0.0022; Test#8

F= 7.67, P= 0.0004; Test#9 F= 10.02, P= 0.0001; Test#

10 F= 10.88, P= 0.0.0002; Test# 11 F= 9.10, P= 0.0001;

and Test# 12 F= 5.46. P= 0.0025.

In nine of the tests, control traps without lures caught few

moths, but mean catches per trap were 10.8 f 2.1 for

generation 1 (Test #9) in Alabama, and 10.6 rt 2.6 for

generation 1 (Test #IO) and 23.6 f 10.9 generation 2 (Test

#II) in Virginia. NPTM populations were very high during

these three tests and trap catches for the best lures in each

test were 9 to 28 times those for the control traps.

No single lure was best in all locations and generations and

there was a significant treatment by location interaction

0=56,248 = 8.50, P = 0.0001). Traps with the T&e@ red septa

lures, Ecogen@ red septa lures, and Sentry@ fiber lures

caught significantly higher numbers of moths than the

Hercon luretapes@ (figs. 2-5). Custom red and gray septa

lures from batch 1 performed well (figs. 2-5) and catches in

5 9
Figure l-Commercial traps used in the trap design tests: (A) Pherocon 1 C@ wing trap (with brown plastic top), (8) Pherocon 1 C@ wing

trap (with white plastic top), (C) Trece Pherocon II@ trap (white), (D) Pherocon CP wing trap (white), (E) Trece Delta@ trap (green), (F)

Trece Delta@ trap (orange) (G) Pherocon Bucket@ trap (yellow/white), and (H) Pherocon Bucket@ trap (green).

60
Lure lest # 1 -- 1st NPTM Generation

11 March - 5 May, 1997

Oconee County, Georgia

120

110

100

P 90

P i ab

120

110 1

100 -I

0 90 -

b

2 80-

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2 70-

;

2i

60-

ii 50 -

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I 30 -

Lure Test # 2 - 2nd. NPTM Generation

3 June - 8 July, 1997

Madison County, Georgia

Fiaure P-Catches of NPTM males in Pherocon IV’ wina traos baited with custom and commercial lures, Georgia Piedmont,

1997.

-

traps with the three best commercial baits were generally

not significantly different from the batch 1 custom lures.

Custom lures from batch 2 performed poorly in all tests

where they were used (custom red septa lures, tests 6, 9,

11, and 12 and custom gray, tests 6, 11, and 12) apparently

because these septa were improperly loaded.

Trap Design Tests

Catches differed significantly among treatments in Trap

Design Test # 1 (F = 15.26, P = 0.0001) and Trap Design

Test # 2 (f = 16.73, P = 0.0001). Pherocon wing traps@, with

either the white or brown top, captured significantly more

moths than the other traps tested in both tests (fig. 6). The

Pherocon II@ trap captured only about half as many moths as

wing traps. Other traps tested were less effective and caught

significantly fewer moths than the wing traps. The poorest

traps were the orange and green Trece Delta Traps? and the

Pherocon Green Bucket@ trap. These traps were also late in

predicting first male NPTM catches in both tests (table 1).

Trap Color Tests

Catches differed significantly among treatments in Color Test

# 1 (f = 4.86, P = 0.0003) and Color Test # 2 (F = 3.94, P =

0.0016). Pherocon 1 C@ wing traps painted red, yellow, blue

or gray caught significantly fewer moths than unpainted traps

in Color Test #I, but only blue or gray traps had lower

catches in Color Test # 2 (fig. 7). Unpainted Pherocon 1 C@

wing traps consistently caught more moths than painted

traps. Gray traps had the lowest catches.

Lure Longevity Test

Catches of NPTM males in Pherocon 1 C? wing traps with

Trece Red rubber NPTM lures were replaced weekly did not

differ significantly (F = 2.2, P = 0.2049) from those for traps

where the lures were not changed (fig. 8). Differences in the

mean number of NPTM males caught per trap between

treatments, within each trapping period were similar and the

treatment by trapping period interaction was not significant

(f = 0.0, P =0.947).

Optimum Dosage and Ratio of E9-12:OAc : E9,Ell12:OAc Test

Catches of NPTM males in Pherocon 1 C@ wing traps

differed significantly among treatments (F = 3.30, P = 0.020)

with red rubber septa lures containing different dosages of

E9-12:OAc : f9,Ell-12:OAc (2O:l). The treatment by

trapping period interaction was not significant (F = 0.91, P =

0.637). Traps with the 0.125mg lures caught significantly

more moths than traps without lures or with 1 mg lures (fig.

9). There was no significant difference among catches for

traps with 0.125, 0.25, 0.5, or 2 mg lures.

6 1
8 0

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Lure Test # 3 -- 1st. NPTM gene,ration

6 February - 7 March, 1997

Beaufort County, South Carolina

80

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lI -

rLure lest # 5 - 3rd. NPTM Generation Lure Test # 6 - 4th. NPTM Generation

20 June - 5 July, 1997 21 August - 17 September, 1997

Bullock County, Georgia Bullock County, Georgia

80

70

a 60

l!

$ 50

s?

E

%

40

3 30

c

c= 20

80

1

70 -

a 60 -

; 50-

z

0,

E"

i

40-

30-

t

c

3

= 20-

Figure 3-Catches of NPTM males in Pherocon 1 C@ wing traps baited with custom and commercial lures, South Carolina and

Georgia Coastal Plain, 1997.

62
Lure Test # 7 - 3rd. NPTM Generation

?I July - 8 August, 1997

Macon County, Alabama

Lure Test # 8 - 4th. NPTM Generation

19 August - 23 September, 1997

Macon County, Alabama

130

120

110

I

b

100

0

f

f

90

t 80

z

$i 70-

2 60-

-it2 50-

2

2

40-

30 - a

0 rsdrcptr QfwYwpla Lumbps, niwrs mdsespo redaepw

Treatment

g 90

$ 80

Treatment

Lure Test # 9 - 1st. NPTM Generation

6 March - 9 April, 1998

Macon County, Alabama

eb

T

Treatment

Figure 4-Catches of NPTM males in Pherocon lC@ wing traps baited with custom and commercial lures, southeastern Alabama, 1997-1998.
Lure Test # 10 - 1st. NPTM Generation

17 April -19 May, 1997

Southampton County, Virginia

350

350

a

325

325

300

300

"7C

Lure Test # 11 - 2nd. NPTM Generation

II June - 21 July, 1997

Southampton County, Virginia

Lure Test # 12 - 3rd. NPTM Generation

3 September - 3 October, 1997

Southampton County, Virginia

350 ,

325

300

275 i

3 250 -

is! 225 -

g 200 -

E 175 -

5

g 150-

E

2 125,

Treatment

Figure CL-Catches of NPTM males in Pherocon I(? wing traps baited with custom and commercial lures, southeastern Virginia, 1997.
Trap Design Test # 1 Trap Design Test # 2

1 5 May - 9 June, 1998 20 May -29 June, 1998

Bullock County, Alabama Oglethorpe County,Georgia

250 -T

Trap design

Figure 6-Catches of NPTM males in eight commercial traps baited T&c& red n Jbber septa lures, Alabama and Georgia, 1998.

f 175

i

z" 150 sT

h

i!

i

125

100

2

3

s 7 5

5 0

2 5

sb

T I

Trap design

Table I-Dates for first male NPTM catches 0 and dates on which catch equaled or

exceeded an average of 1 moth/trap 46 for eight types of traps baited with Trece red rubber

lures, 1998

Trap type

Test # 1 - Alabama

5/158 5/19 5122

Test #2 - Georgia

5126 5129 6101 6104 6108

Pherocon 1 C - White

Pherocon IC - Brown

Pherocon II

Pherocon 1 CP

Delta - Green

Delta - Orange

Bucket- White/yellow

Bucket - Green

a Traps checked for moths at 3-4 day intervals.

Catches of NPTM males in Pherocon 1 C@ wing traps

differed significantly among treatments (F = 3.24, P =

0.0138) with red rubber septa lures containing different

ratios of E9-12:OAc : E9,El I-12:OAc. The treatment by

trapping period interaction was significant (F = 1.64, P =

0.0216) but too few moths were caught during each

trapping period to examine the relative lure effectiveness

over time. Traps with lures containing pheromone ratios of

15, l:lO, and I:20 caught the highest number of moths and

did not differ significantly from each other (fig. 9).

DISCUSSION AND CONCLUSIONS

Our tests results have important implications for NPTM pest

management. They show that not all NPTM lures or traps
70

6 0

B

b 50

s

8

a, 40

E”

b

3 30

f

sz

5

w 20. I

IO -

oTrap Color Test # 1

26 June - 24 July, 1998

Trap Color Test # 2

Bullock County, Alabama

7 August - 4 September, 1998

Bullock County, Alabama

ab

Trap color WI color

Figure 7-Catches of NPTM males in Pherocon lC@’ wing traps painted

1998.

Longevity of Trece Red Septa Lures

11 July - 8 August, 1997

Macon County, Alabama

--+ Replaced (Total = 191)

4-- Unchanged (Total = 194)

0” I I

I

15 18 22 25 2 9 1 5 0

July August

Figure 8-Catches of NPTM males in Pherocon lC@ wing traps

baited with Trece red rubber septa lures changed weekly or

unchanged, Alabama, 1998.

b

eight colors and baited with Trece red rubber septa lures, Alabama,

are equally effective in attracting male moths. Three

important factors which affect the performance of NPTM

lures include lure type, dosage, and the E9-12:OAc :

E9,Ell-12:OAc ratio. Several possible scenarios involving

these factors may explain the differences in lure

performance and poor summer efficiency of the NPTM traps.

First, both NPTM pheromone components may volatilize and

dissipate because of the high ambient temperatures,

causing the lures to quickly lose their effectiveness. Lures

with higher dosages may be needed during the hot summer

and fall months, than in the cooler spring months.

Second, high ambient temperatures in the summer may

increase the loss of E9-12:OAc on NPTM lures to a rate high

enough to inhibit NPTM males. Traps baited with 1 mg of

Zll-16:OAc lures catch only half as many southern pine

coneworm, D. amatella moths, as lures with 0.3 or 0.1 mg

(Meyer and others 1986).

Third, summer temperatures may cause E,E-9,11-12:OAc to

rapidly dissipate or degrade, changing the optimum ratio of

the two components and eventually leaving only the major

compound. Without the minor component, E9-12:OAc alone

is a weak attractant (Hill and others 1981). Exposure to UV

light during the long summer days may also cause

isomerization of the diene, E,E-9,11-12:OAc, to an inactive

isomer, changing the 955 ratio of the pheromones. Rapid

isomerization of conjugated dienes occurs on red natural

rubber septa lures, but it is minimal on gray butyl rubber

septa (Brown and McDonough 1986).

66
Pheromone Ratio Test

20 March - 5 May, 1997

Oconee County, Georgia

Pheromone Load Test

20 March - 5 May, 1997

Oconee County, Georgia

b

0

lhhited 0.125~ 0.25 mg

l!2 IO

!s bc

0,E 8

3

g 6

z

3

z” 4

2

0

1 :a0 1:20 130 1:s

E9-12:Ac: E,E-9.1%12:Ac (203) I Red rubber Septa

Figure Q-Catches of NPTM males in Pherocon lC* wing traps baited with custom gray rubber septa lures loaded with different amounts or

ratios of pheromones, Georgia, 1997.

Fourth, the optimum ratio of the two synthetic NPTM

pheromone components for attracting males may change

during the summer months. For example, the omnivorous

leafroller moth, Playnofa sfulfan (Walsingham), produces the

same ratio of its two-component pheromone during three

flight periods in May, August and October, but the best

pheromone component ratios in lures change for each

generation (Baker and others 1978).

Finally, if trap catches of NPTM are low because males have

a shorter life span (Asaro and Berisford 2001 b) or are less

responsive during the summer months than in the spring or

because the lures are not competitive with high numbers of

feral females, it may be impossible to develop a “better lure”

for hot weather conditions.

The traps we tested varied in both the size of the opening

through which the moths entered the trap and the area of

sticky trap surface. For example, the Pherocon Delta traps@

have a smaller opening and less sticky surface than any of

the other cardboard sticky traps we tested. In addition, we

closed the end panels as indicated in the instructions

provided with the trap. Delta traps with the end panels fully

open, should be tested again to compare their performance

with wing traps. Although trap color influenced trap catch, it

may not be as important for NPTM males as for some other

insects and commercially available white wing traps appear

suitable for NPTM.

Traps or lures with poor efficacy will mislead forest

managers or Christmas tree growers about the onset of

moth flight and moth population levels. Using the most

effective pheromone lure is extremely important when traps

are used to detect the first NPTM moths for initiating degreeday models for predicting optimum spray dates. When traps

are used to monitor tip moth populations and predict the

need for control, consistent performance of lures and traps

will be even more important and it will be necessary to adopt

a standard lure and trap combination. Our studies suggest

that further research to develop a more effective and reliable

lure may be warranted.

ACKNOWLEDGMENTS

We extend our special thanks to Marc Davidson and Jimmy

Seckinger, International Paper Company: Kason Furnas,

Department of Horticulture, Auburn University: and Chris

Crowe and Mike Cody, Southern Research Station, USDA

Forest Service for locating the study sites, installing the tests

and monitoring the traps. Mark Dalusky, Department of

Entomology, University of Georgia provided helpful

suggestions. We thank Dan Miller, Southern Research

Station, for reviewing the manuscript. International Paper

Company (formerly Union Camp Corporation) and

Champion Paper Company allowed us access to their pine

plantations. Funding was provided by the Union Camp

Corporation, the USDA Forest Service Southern Research

Station, and the University of Georgia-Industry Pine Tip

Moth Research Consortium.

6 7
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68


Berisford, C. Wayne; Grosman, Donald M., eds. 2002. The Nantucket pine tip moth: old

problems, new research. Proceedings of an informal conference, the Entomological

Society of America, annual meeting. 1999 December 12-16. Gen. Tech. Rep. SRS-51.

Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station.

68 p.

The Nantucket pine tip moth, Rbyacionia frustrana (Comstock) has become a more prevalent

pest in the South as pine plantation management has intensified. The Pine Tip Moth Research

Consortium was formed in 1995 to increase basic knowledge about the moth and to explore

ways to reduce damage. A conference was held in 1999 at the Entomological Society of

America annual meeting in Atlanta, GA; to review some recent research on the moth. Papers

presented at the conference included work on damage assessment (impact) and a review of

previous attempts to quantify tip moth damage, interactions of the moth with different forest

management practices and the relationship with intensive management, effects of herbicide

and insecticide use on tip moth parasitoids, evaluations of different types of insecticides for

tip moth control, methods for optimizing chemical control through more precise timing, potential

for augmenting tip moth egg parasites by releases of laboratory-reared parasitic wasps, a

review of the potential opportunities for using pheromone traps to predict tip moth infestation

density and damage and evaluations of different pheromone trap designs and lures.

Keywords: Biological control, chemical control, forest management, growth impact,

pheromone traps, pine tip moth, Pinus faeda, Rhyacionia frustrana.
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