United States

Department of

Agriculture

Forest Service

waun

ccI- -

Reduces F&form F&t Infection

on Loblolly Pine

Southeastern Forest

Experiment Station

Research Paper

SE-270

H.R. Powers, Jr.

D.M. Stone
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 pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides

and pesticide containers.

July 1988

Southeastern Forest Experiment Station

P.O. Box 2880

Asheville, North Carolina 28802
Control of Tip Moth by Carbofuran

Reduces Fusiform Rust Infection

on Loblolly Pine

HR. Powers, Jr., Research Plant Pathologist

Southeastern Forest Experiment Station

Athens, Georgia

D.M. Stone, Research Forester

North Central Forest Experiment Station

Grand Rapids, Minnesota

ABSTRACT

The systemic insecticide carbofuran was applied to the soil under

planted loblolly pines in studies near Aiken, SC, at ages 2 through 5.

As expected, the insecticide sharply reduced tip-moth damage and

increased the height of LLyear-old saplings, compared with untreated

controls. Untreated trees not only had more tip-moth injury but also

had significantly more fusifonn rust infections. Carbofuran itself did not

have any fungicidal effect which could have been responsible for the

lower incidence of rust among the treated trees. Since carbofuran

treatment not only reduced damage from tip moth but also decreased

rust infection, these results may prompt new interest in the economics

of tip-moth control.

Keywords: Pinus taeda, Cronartium quercuum f. sp. fusiforme, Rhyacionia

frustrsns.

Loblolfy pine (pinus teeda L.) is the forest

tree species most often planted from Maryland

through Texas. In this area, growth of loblolly pine

usualfy equals or exceeds that of other pine species,

and it grows well on a wide variety of sites. Across

much of this area, loblolly pine is subject to attack

by both tip-moth and fusiform rust. The tip-moth

problem is caused by a complex of several closely

related species, the most common of which is the

Nantucket pine tip moth (Rhyacionia ffusfrana

(Comstock)). Tip-moth damage often is so prevalent

that it is difficult to find unaffected seedlings in

young plantations. Fusiform rust is caused by

Cronartium quercuum (Berk.) Miyabe ex Shirai f.

sp. fusiforme. Although fusiform rust infection is

not quite as common as tip-moth attack, disease

incidence as high as 95 percent occurs in the

high-rust-hazard zone that extends from South

Carolina through Georgia and into Alabama (Phelps

1973). The susceptible areas on the pine host for

both pests are young, succulent shoot tissues.

There has been considerable interest in

tip-moth damage because of its prevalence on

loblolfy pine. There seems file doubt that heavy

attacks reduce height growth in the early years of

a plantation (Cade and Hedden 1987). However,

several studies have shown that height differences

caused by tip-moth attack disappear between

ages 15 and 28 (Beale 1967; Williston and Barras

1977). The study by Cade and Hedden also showed

that treatment to control tip moth is marginalfy

cost effective onfy in a thinned sawtimber regime.

From a practical standpoint, they did not recommend operational tip-moth control. It was felt that

even slight changes in insect damage levels, site

productivii, interest rates, or other factors would

cause the treatment to be uneconomical. At present,

therefore, tip-moth damage is simply tolerated.

Field control of fuslform rust with chemicals is also

considered economically unfeasible. However,

large-scale programs to develop rust-resistant

pines have been underway for several years

(Powers and others 1976; Zobel and others 1971)

and rust-resistant strains of both loblolly and slash

pines are now available for reforestation in high-rusthazard areas.

One approach to this dual problem of insect

and disease damage is to plant a species less

susceptible than lobfolfy pine to tip-moth attack

and rust infection. Slash pine (Pinus elliottii Englem.

var. e//ioffi& the other southern species widely

used in reforestation, is less frequently attacked

by tip moth and has a growth advantage over

loblolly in the early years of a plantation. Over a

complete rotation, however, loblolly pine usually

outgrows slash even when the loblolly has early

tip-moth infestations. Unfortunately, both loblolly

and slash pine are susceptible to fusiform rust,

which is the most damaging disease of southern

pines (Powers and others 1981). The mortality of

slash pines due to fusiform rust is usually greater

than that of IobkMy pine except in the southernmost

part of the loblolfy range in Florida (Powers and

others 1975). As a result, most forest managers

live with the damage caused by tip moth and try

to obtain rust-resistant loblolly pine seedlings to

reduce damage from the disease.
Tip moth larva in a terminal shoot of lob/o//y pine.

This study was designed to determine what

effect the control of tip moth by carbofuran, a

systemic insecticide, would have on subsequent

infection of both rust-resistant and susceptible

strains of loblolly pine by the fusiform rust fungus.

Materials and Methods

Rust-resistant seedlings were grown from a

mixture of seeds collected from 20 of the most

rust-resistant loblolly pine clones in the South.

Control seedlings were commercially available

improved loblolly from a general production

orchard. All seedlings were grown in a nursery by

standard practices and planted on the Savannah

River Plant facility near Aiken, SC. The field design

was a split plot with 10 rows each of resistant and

control seedlings as the main plots. Within each

of two replications were eight randomized blocks,

either with or without carbofuran treatment. Each

carbofuran-treated or untreated block measured

approximately 27 by 30 m, and originally contained

110 to 140 seedlings. Trees were machine planted

approximately 2 m apart with 3 m between rows.

Carbofuran (10% A.I. formulation) was applied

to the soil around designated seedlings at the

rate of 30 g/seedling in March of the second through

fiih years of the study. The carbofuran was

incorporated into the soil with fire rakes. At the

end of the fifth growing season, tree heights were

measured, and rust infection and tip-moth damage

were evaluated. Trees were recorded as either

rust infected or healthy, based on whether any

rust galls were present on either stems or branches.

Tip-moth infestations were evaluated on the basis

of whether or not damage occurred on any of 10

randomly sampled current-year shoots from each

tree.

Carbofuran is taken up by seedling roots

and translocated to the young shoot tissues that

are the primary targets for rust infection. One

possible mechanism for a reduction in rust

incidence after insecticide application would be

carbofuran toxicity to the mycelium of the rust

fungus as it penetrates young shoot tissues. A

greenhouse study with young seedlings was

designed to evaluate this possibility. Ten trays,

each with 20 loblolly seedlings, were assigned to

each of four concentrations of carbofuran: 0, 1, 2,

2
and 4 g/tray. Carbofuran was applied approximately

I month after seedling germination. Three weeks

later the seedlings were artificially inoculated with

the fusiform rust fungus by applying a highly

concentrated spray of basidiospores (Powers and

Matthews 1979). The aeciospores used to produce

this inoculum were from a mass collection adjacent

to the test site near Aiken, SC. Infection data were

based on the number of seedlings with actively

growing galls after 9 months.

Results

As expected, significantly fewer resistant

than control saplings in the field test were infected

with fusiform rust. Among all control saplings,

55.5 percent were infected with either stem or

branch galls, compared with 25.4 percent of the

resistant seedlings (table I). Unexpected, however,

was a highly significant difference in rust infection

between carbofuran-treated and untreated

saplings. Cf the untreated saplings, 46.3 percent

had evidence of rust infection, as opposed to 34.6

percent infection of treated saplings. The decrease

in rust among saplings receiving carbofuran was

evident for resistant as well as susceptible seed

sources. Among resistant saplings, infection

percentages were 18.5 percent for seedlings

treated with carbofuran and 323 percent for the

untreated ones. Among control saplings, percentages were 50.8 with carbofuran treatment and

60.3 percent without.

The carbofuran treatment also gave good

control of tip moth. Only 17.9 percent of the trees

treated with the insecticide had evidence of tip-moth

damage. About two-thirds of the trees that did not

receive carbofuran were damaged by tip moths.

There was no significant difference in tip-moth

infestation between the resistant and control seed

sources.

Carbofuran application also produced a

significant (0.05 level) increase in height. The

carbofuran-treated trees averaged 3.7 m at age 5,

compared with 3.2 m for the untreated trees. There

was no significant difference in height between

the rust-resistant and control trees.

In the greenhouse study, there were no

differences in the amounts of rust infection on the

seedlings after treatment with the different levels

of carbofuran. Infection rates were high for all

treatments (83-90% infeqtion). The untreated control

seedlings had almost as much infection (88%) as

the seedlings with the highest level of carbofuran

ww.

Treatment

Trees infected

with rust

'frees showing

damage by tip moth height

Carbofuran:

Resistant trees

Control trees

Untreated Control:

Resistant trees

Control trees

Resistant trees (Mean)

Control trees (Mean)

Percent Percent

34.6* 17.9*

18.5 18.5

50.8 17.3

46.3a 66.8*

32.3 65.5

60.3 68.0

25.4' 42.0d

55.5= 42.6d

Meters

3.7b

i:::

3.2b

;::

%alues for carbofuran-treated trees

and untreated controls differ significantly at the 0.01 level.

%lues for resistant and control trees

differ significantly at the 0.01 level.

b

dvalues for resistant and control trees

Values for carbofuran-treated trees do not differ significantly at the

and untreated controls differ sig- 0.05 level.

nificantly at the 0.05 level.
Dkcueelon

The study was originally designed to detect

any effect on rust incidence of controlling tip moths

with carbofuran, and to test the rust resistance of

the two seed sources. The differences in rust

susceptibility between resistant and control seed

sources were anticipated, as was the effectiveness

of carbofuran in controlling tip moth (Nord 1978).

The reduction in rust incidence on trees treated

with carbofuran is more difficult to explain. It was

assumed that carbofuran, which contains some

nitrogen in its formulation, would probably stimulate

growth, and’1 did do so. Anything that stimulates

growth of the host, such as fertilizer application or

intensive site preparation, increases the amount

of rust-susceptible tissue and usually results in an

increase in the incidence of rust, Therefore, an

increase rather than a decrease in rust incidence

was expected where carbofuran was applied.

The results of the greenhouse test demonstrated that the reduction in rust incidence among

carbofuran-treated trees was not caused by any

fungitoxic effect of the insecticide itself. In that

test, rust incidence on the controls was very similar

to that on seedlings receiving the highest rates of

the insecticide. Therefore, some mechanism other

than carbofuran toxicity to the fungus must be

sought to explain reduced rust infections on

carbofuran-treated trees in the field study.

It has been shown that tip moth attacks

reduce the number of shoot tips and tip growth

(Lashomb 1978) so additional target area for

infection is not the reason for the increased rust

incidence on the untreated trees. Some other

possible explanations for this result are: (1) When

primary shoots of untreated trees are killed by the

tip moth, the resulting flush of secondary shoots

may occur at a time of higher basidiospore

production. (2) Tip-moth injury may provide an

infection court for the fusiform rust pathogen.

Evaluation of these alternative explanations will

await further experimentation. Meanwhile, the

interaction between these two pests may cause

forest managers to consider controlling tip moth,

because it is apparent that the untreated seedlings

not only had more tip-moth damage but also

considerably more rust. It may therefore be

worthwhile to reevaluate the economics of field

control of the tip moth.

Literature Cited

Beal, Raymond H. 1967. Heavy tip moth attacks reduce earty growth of

bbblly and shortleaf pine. Res. Note SO-54 New Orleans, LA: U.S.

Department of Agriculture, Forest Service, Southern Forest Experlmm statbn. 3 pp.

Cade, Stephen C.; Hedden, Roy L 1987. Qrowth impact of pine tip

moth on bbbffy pine pbntatbns in the Ouachita mountains of

Arkansas. Southem Journal of Appked Forestry 11:128-133.

La&tomb, James H. 1978. Impact studies of Nantucket pine tip moth

populatbn~ on bbkMy pine. Envfronmentaf Entomobgy 7:919-912.

Nwd, John C. 1978. Field test of granular carhofuran for control cf

ths Nantucket pins tip moth in pine pbntatkxts. Res. Note SE-261.

Asheville, NC: U.S. Defxrtment d Agriculture, Forest Service,

Southeastern Forest Experiment Statbn. 8 pp.

Phefps, W.R. 1973. Fusifom~ rust in&fence survey for 1971-1973.

Atfanta, (3A: U.S. Department of Agdculture, Forest Service, Boutheastem Area, State & Pdvate Forestty. 69 pp.

Powers, H.R., Jr.; Kraus, John F.; Duncan, H.J. 1976. Devebpment of

rust-reslstant slash and bbklly pines In Georgia Ga. For. Res

Pap. 87. Macon, QAI Georgia Forest Research Council. 9 pp.

Powers, H.R.. Jr.; McCfure, J.P., Knight, HA.; Dutmw, Q.F.

1975. Fusifomt rust: forest survey in&fence data and flnancfal

impact in the South. Res. Pap. SE-127. AsheviUe, NC: U.S. Depattmerit of Agriculture, Forest Se&e, Southeastern Forest Expsriment

statbn. 16 pp.

Powers, HR.. Jr.: MMhews, F.R. 1979. Interactions between virulent

isolates of Cfonaahm quercuum 1. sp. fusifornm and bhlotfy pins

famiri af vafyiqr resistance. Phytopathokqy 69~720-722

Powers, H.R., Jr.; Schmii, R.A.; Snow, G.A. 1981. Current status

and nmmgmmt of fuslfonm rust on southern pines. Annual Review

Phytopathdosy 19:353-371.

Wtllbton, H.L; Banas, SJ. 1977. Impact of tip moth injury on growth

and yield of 15year4d bhblfy and shortleaf pine. Res. Note SO-221.

New Orleans, LA: U.S. Department of Agriculture, Forest Service,

Southern Forest Experiment Statbn. 6 pp.

Zohef, B.R.; Blair, R.; Zoerh, M. 1971. Using research data-disease

reslstanca Journal of Forestry 6~~.
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Powers. H-R.. Jr.; Stone, D.M. Powers, H.R.. Jr.; Stone, D.M.

Control of tip moth by carbofuran reduces fusiform rust infection

on loblolly pine. Res. Pap. SE-270. Asheville, NC: U.S. Department

of Agriculture, Forest Service, Southeastern Forest Experiment

Station. 1988. 4 pp.

Control of tip moth by carbofuran reduces fusiform rust infection

on loblolly pine. Res. Pap. SE-270. Asheville, NC: U.S. Department

of Agriculture. Forest Service, Southeastern Forest Experiment

Station. 1988. 4 pp.

Carbofuran, a systemic insecticide, was applied to the soil under

planted loblolly pines near Aiken. SC. at ages 2 through 5. The

insecticide sharply reduced tip-moth damage and increased the height

of 5-year-old saplings, compared with untreated controls. Treatment

also reduced incidence of fusiforn rust, but carbofuran did not have

a fungicidal effect.

Csrbofuran, a systemic insecticide, was applied to the soil under

planted loblolly pines near Aiken. SC. at ages 2 through 5. The

insecticide sharply reduced tip-moth damage and increased the height

of 5-year-old saplings. compared with untreated controls. Treatment

also reduced incidence of fusiform rust. but carbofuran did not have

a fungicidal effect.

REYWORL%: Pinus taeda, Cronartium quercuum f. sp. fusifome.

Rhyacionia ftustrana.

KRYUORDS: Pinus taeda. Cronartium quercuum f. sp. fusiforme.

Rhyacionia frustrana.

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Agriculture, is dedicated to the principle of

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