U.S. Department of Agriculture

Forest Seroice Research Note S E- 279 June 1979

LABORATORY SCREENING AND FIELD BIOASSAYS OF

INSECTICIDES FOR CONTROLLING THE BALSAM

WOOLLY ADELGID IN SOUTHERN APPALACHIA1

by F. L. Hastings, P. J. Barry, and I. R. Ragenovich2

ABSTRACT.-Two concentrations of 13 insecticides and 3 fatty acids were screened in the

laboratory against the balsam woolly adelgid (Adelges piceae (Ratz.)). Effkacy was judged on the

percentage of dead adults and the number of living crawlers 24 hours after application. The top

candidate materials, including lindane, were field bioassayed. Permethrin (Pounce@ or Ambush@),

chlorpyrifos (Dursban@) and chlorpyrifos-methyl (ReIdan@) were identified as potential replacements for lindane in controlling this insect.

Keywords: Adelges picea, Fraser fir, Abies fraseri, insecticides, insecticidal screening, field bioassay.

The balsam woolly adelgid (BWA) is a serious pest of true firs, Abies spp., and annually kills

thousands of Fraser fir (Abies fraseri Pursh.) in

the Southern Appalachians.” This insect threatens the natural beauty of the area and damages

unprotected Christmas trees in plantations in

North Carolina, Virginia, and Tennessee. Applying pesticides to control the BWA in a forest may

never be practical, but it is possible along roadsides and it may be necessary in Christmas tree

plantations. For these purposes, environmentally

acceptable insecticides are needed.4 Lindane, the

only material registered for this use, is currently

on the Environmental Protection Agency’s

Rebuttable Presumption Against Registration list.

‘Mention of tradenames in this article is solely to identify

materials and equipment used, and does not imply endorsement

by the U. S. Department of Agriculture.

‘Hastings is Principal Entomologist, Forestry Sciences

Laboratory, Research Triangle Park, North Carolina; Barry is

Supervisory Entomologist, Southeastern Area, State and Private Forestry, Asheville, North Carolina; and Ragenovich is

Entomologist, Region 3, State and Private Forestry, Albuquerque, New Mexico.

“Amman, G. D.. and C. F. Speers. 1965. Balsam woolly

aphid in the Southern Appalachians. J. For. 63:18-20.

4Puritch, George S. 1975. The toxic effects of fatty acids

and their salts on the balsam woolly aphid, Adelges piceae

(Ratz.). Can. J. For. Res. 5:515-522.

Here we report an effort to evaluate other chemicals which might well replace lindane if they

prove effective in large-scale field tests.

MATERIALS AND METHODS

Lab bioassay.-During the fall of 1976, the

bole of a Fraser fir heavily infested with BWA was

cut into bolts which were individually wrapped

and transported via air-conditioned vehicle to the

laboratory. The bolts were maintained at 202 1°C

throughout the tests and subsequent observations. Round samples of bark 18 mm in diameter

were examined to estimate the insect population.

The number of adults per sample ranged from 10

to 20, and a number of eggs and crawlers were also

observed.

Bolts were subdivided into 20-cm sections

and each end was waxed. These were placed on a

turntable in a fume hood and sprayed to the point

of runoff with aqueous 0.1 and 0.5 percent solutions of 13 insecticides and 3 fatty acid emulsions.

The emulsions were prepared by adding 0.1 percent T&on-X-100, then sonifying (20 set) with a

Beckman Polytron Disintegrator@. The materials

were applied with an air-driven atomizer similar

to a pressurized garden-type sprayer. After 24

Southeastern Forest Experiment Station - Asheuille, North Carolina
hours, the mortality of adults and number of living sprayer to the point of runoff. The bolts were

crawlers were determined by examining a circular placed under the forest canopy, and the mortality

disc of bark removed from each bolt with an 18- of adults and the number of living crawlers were

mm-diameter cork borer. Insects were counted at determined at 24 hours. These bolts were not

40-power magnification, and at least 10 adults heavily infested; therefore, usually 5 to 7 discs

were examined for each treatment. Adults were (18-mm diameter) were examined before the

judged alive if they moved after being prodded. mortality of 20 adults was determined.

Field bioassay.-During August of 1977,

four Fraser firs infested with BWA were felled on

Roan Mountain in North Carolina and cut into 30

cm bolts. Both ends of these bolts were waxed,

and the bolts from each tree were randomized and

sprayed with 0.25 and 0.5 percent concentrations

of aqueous solutions of the materials selected

from the laboratory study. The lower concentration was increased to 0.25 percent for the field

studies because some crawlers in the lab bioassay

survived the 0.1 percent concentration. The bolts

from each tree served as a replication, and each

replication contained two unsprayed bolts as controls. To assure homogeneous coverage, bolts

were rotated on a portable turntable while being

sprayed with a Kinkelder@ low-volume power

Statistics.-Because the number of observations was small, an assumption of normality could

not be made; therefore, a standard analysis of

variance was not used. Differences between the

0.25 and 0.50 percent concentrations of each insecticide were analyzed by a nonparametric

Wilcoxon test. Finally, differences among insecticides were analyzed by Duncan’s multiple range

test.

RESULTS AND DISCUSSION

Based upon adult and crawler mortality,

permethrin, methomyl, and lindane were the most

effective materials in the preliminary laboratory

screening (table 1). These were closely followed

Table I.-Results for laboratory bioassay of 13 insecticides and 3 fatty acids against the balsam

woolly adelgid

0.1 percent concentration 0.5 percent concentration

Compound Adults, Crawlers, Adults,

dead’ surviving dead

Crawlers,

surviving

Permethrin

Carbaryl

Methomyl

Diazinon

Diflubenzuron

Carbophenothion

Etrimfos

Pirimphos-ethyl

Chlorpyrifos

Chlorpyrifos-methyl

Lindane

Phosmet

Fenitrothion

Caprylic acid’

Capric acid2

Laurie acid2

Controls3

Percent Number Percent Number

100 0 100 0

80 I 90 I

100 0 100 0

100 0 40 IO

20 20 90 1 0

90 1 100 2

90 12 100 1 0

100 2 100 2

100 2 100 0

100 1 0 100 0

100 0 100 0

100 7 50 9

100 20 100 IO

IO 28 0 15

60 14 90 15

100 20 30 15

0 >30 0 >30

‘Mortality determined 24 hours after treatment.

“Emulsified with 0. I percent Triton-X- 100 using a Beckman Polytron Disintegratof.

“Four controls.
by chlorpyrifos, pirimiphos-ethyl, and chlor- in mortality for adult BWA between the 0.25 and

pyrifos-methyl; carbophenothion also showed 0.50 percent concentrations for any of the six

promise. The decrease in mortality with an in- insecticides. Therefore the 0.25 and 0.50 percent

crease in diazinon concentration may have re- data were pooled for each insecticide (eight obsersulted from a mixup in concentrations, but this vations, 160 insects) and subjected to the

cannot be confirmed. Duncan’s multiple range test.

The results of the fatty acid tests were somewhat disappointing since Puritch had shown a

high degree of activity for these acids and their

soaps against dormant and nondormant first

instar BWA (see footnote 4). The lack of efficacy

may result from concentration differences. Our

highest concentration was only one-half the concentration used by Puritch. The recent demonstration of the phytotoxic effect of the soaps of

these particular fatty acids at concentrations required for field efficacy (approximately 2 percent)

has eliminated interest in further study of these

materials. However, the potassium salt of oleic

acid remains a viable replacement for conventional insecticides.”

Lindane, permethrin, chlorpyrifos, and

chlorpyrifos-methyl were highly effective against

the adult BWA (table 2). These compounds

caused greater than 90 percent adult mortality and

there was no significant difference among them.

Dimethoate and methomyl were less effective

than the other insecticides. A similar trend was

seen in the mortality of crawlers. Nine days after

insecticide application, the bolts were reexamined and living crawlers and adults were

found only in the dimethoate treatment.

Compounds that caused 100 percent adult

mortality and eliminated live crawlers at the 0.5

percent concentration were chosen for field bioassay. These were permethrin, methomyl, lindane, chlorpyrifos, and chlorpyrifos-methyl. The

decision to test chlorpyrifos-methyl rather than

pirimiphos-ethyl was based on the longer residual

nature of chlorpyrifos-methyl.” One additional

material, dimethoate, was included because it had

shown promise against the balsam twig aphid

(Mindurus abietnus Koch.).7 The nonparametric

Wilcoxon tests revealed no significant difference

This study has identified three materials

which have potential as replacements for lindane:

permethrin (Ambush’s’ and Pounce@), chlorpyrifos (Dursban@), and chlorpyrifos-methyl

(Reldan@).8

Table 2.-Results of a field bioassay of six insecticides against the balsam woolly adelgid

.‘Puritch, George S. 1978. Personal communication. Can.

For. Serv., Victoria, B.C., Canada.

“Brady, U. E.. and C. W. Berisford. 1976. Expanded

Southern Pine Beetle Research & Application Program, Final

Report. Univ. Ga., Athens.

7Hain, Fred P.. 1978. Personal communication, N. C.

State Univ., Raleigh.

Lindane

Permethrin

Chlorpyrifos

Chlorpyrifos-methyl

Dimethoate

Methomyl

Controls

. . . . . . Percent . . . . . .

84.6 99.4a

88.9 97.5a

82.4 94.4a

83.3 93. la

62.5 79.4b

64.9 69.4b

14.8 18. lc

‘Technical-grade insecticide samples were provided by

FMC Corp., ICI United States, Inc.: Union Carbide Corp.;

Shell Chemical Co.: Ciba-Geigy Corp.; Thompson Hayward

Chemical Co.; Stauffer Chemical Co.; Sandoz, Inc., and Dow

Chemical Co.

‘Mean values for eight replicates; not tested for statistical significance due to low numbers of crawlers.

*Means followed by the same letter do not differ significantly according to Duncan’s multiple range test (P <

0.01).

This publication reports research involving pesticides It does not contain recommendatidns 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: Pestxldes can be m~ur~ous to humans, domestic anmnals, desrable plants, and fish or other

be* wildlife--if they are not handled or apphed properly Use all pesticides selectively and carefully Follow

“-.- recommended mact~ces for the dlsoosal of surplus msticides and pesticide containers.
The Forest Service, U.S.

Department of Agriculture,is

dedicated to the principle of

multiple management of the

Nation’s forest resources for

sustained yields of wood,

water, forage, wildlife, and

recreation. Through forestry

research, cooperation with the

States and private forest

owners, and management of

the National Forest and

Grasslands, it strives - as

directed by Congress - to

provide increasingly greater

service to a growing Nation.

USDA policy does not permit discrimination because

of race, color, national origin, sex or religion. Any

person who believes he or she has been discriminated

against in any USDA-related activity should write

immediately to the Secretary of Agriculture,

Washington, D.C. 20250.

*U.S. GOVERNMENT PRINTING OFFICE: 1979--840016/4SO7 REGION NO. 4