Control of the Gypsy Moth and Other Insects with Behavior-Controlling

Jun 1, 1976 - Although insecticides continue to be our major means of defense against insects that attack our food, fiber, and other agricultural prod...
0 downloads 0 Views 2MB Size
Download PDF
7 Control of the Gypsy Moth and Other Insects with Behavior-Controlling Chemicals MORTON BEROZA Agric. Res. Serv., USDA, Beltsville, Md. 20705 Current address: 821 Malta Lane, Silver Spring, Md. 20901

Although insecticides continue to be our major means of defense against insects that attack our food, fiber, and other agricultural products, difficulties related to the use of i n secticides have generated a sustained search for alternative means of insect control, or at least some means of reducing the use of insecticides required for pest management. In this regard, the behavior-controlling chemicals, and insect sex attractants in particular, have received considerable attention during the past several years. The present paper describes some of the recent research conducted by the USDA and cooperators with behavior-controlling chemicals. Work with the sex pheromone of the gypsy moth (Porthetria dispar (L.)) will be used to illustrate this research for the most part because of the author's major involvement and familiarity with this project. Insect Sex Attractant Pheromones Insect sex attractant pheromones are chemicals emitted by one member of a species to call a mate to it for mating and propagation. These pheromones are highly specific in that they generally affect only their own species, and infinitesimal amounts often induce responses from great distances. Sex pheromones that excite without attracting will not be discussed because their value in pest control has not been demonstrated. In recent years, progress in the identification of the sex attractant pheromones has been extremely rapid. Ten years ago, few had been identified; today, such pheromones are known for several hundred species. This phenomenal progress in an area of endeavor previously considered by many to be unrewarding (or much too difficult) was made possible in part by extraordinary improvements in chemical instrumentation and techniques. Improved chromatographic equipment, materials, and procedures have aided in the separation of the tiny amounts of pheromone in i n sects, and more sensitive spectrometric analyses — along with 99

100

PEST M A N A G E M E N T

WITH

INSECT SEX

ATTRACTANTS

a s s o c i a t e d methodology and devices f o r manipulating microgram amounts of compound — have made p o s s i b l e i d e n t i f i c a t i o n s of these pheromones a t microgram and sometimes submicrogram l e v e l s (1). With new workers e n t e r i n g t h i s f a s t - d e v e l o p i n g f i e l d , pheromone i d e n t i f i c a t i o n s can be expected to continue a t a h i g h r a t e f o r some time to come. U n f o r t u n a t e l y , progress i n the a p p l i c a t i o n of these pheromones i n pest management has not been e q u a l l y r a p i d d e s p i t e the a v a i l a b i l i t y of h i g h l y e f f e c t i v e sex a t t r a c t a n t pheromones f o r many economically important species and d e s p i t e the p o t e n t i a l of c o n t r o l l i n g these pests w i t h non-toxic pheromones used e i t h e r alone or as p a r t of pest management programs. Experimental programs have n e v e r t h e l e s s shown t h a t the use of pheromones i n pest management i s a b a s i c a l l y sound p r a c t i c e and of s u f f i c i e n t promise to warrant increased e x p l o r a t i o n . I t i s a n t i c i p a t e d t h a t pheromones, though g e n e r a l l y not replacements f o r i n s e c t i c i d e s , can help by i n c r e a s i n g the e f f e c t i v e n e s s of i n s e c t i c i d e s and by improving the s e l e c t i v i t y of t h e i r a t t a c k , i . e . , t h e i r a t t a c k w i l l be focused on the damaging pest and not on b e n e f i c i a l or non-target organisms. In the p u r s u i t of t h i s quest, c o n s i d e r a b l e technology must be developed, and a much greater understanding of the e f f e c t of pheromones on i n s e c t s must be acquired before these chemicals can be u t i l i z e d to best advantage. How the Sex Pheromones May be U t i l i z e d The sex pheromones have been used a) f o r d e t e c t i o n and survey of i n s e c t s p e c i e s , b) f o r mass t r a p p i n g , and c) f o r d i s r u p t i o n of the odor-guidance system that normally b r i n g s the sexes together f o r mating and propagation. D e t e c t i o n and Survey. The v a l u e of d e t e c t i o n and survey traps i s w e l l recognized i n pest management c i r c l e s . The capture of i n s e c t s i n traps s i g n a l s the presence of the t a r g e t e d s p e c i e s , and i n s e c t i c i d e s or other c o n t r o l measures may then be d i r e c t e d to the p l a c e where they are needed and when they are needed. In t h i s way, more e f f e c t i v e c o n t r o l has been achieved w i t h l e s s p e s t i c i d e , and the movement of pests i n t o u n i n f e s t e d areas has been q u i c k l y recognized and prevented. Thus, more than 100,000 pheromone traps were set out i n the area east of the M i s s i s s i p p i R i v e r l a s t year t o monitor or d e t e c t i n f e s t a t i o n s of the gypsy moth. A l s o , 17,000 t r a p s , b a i t e d i n t h i s case w i t h s y n t h e t i c l u r e s , are being maintained by the USDA across the southern periphery of the U.S. to detect any a c c i d e n t a l i m p o r t a t i o n of three h i g h l y d e s t r u c t i v e s u b t r o p i c a l pests — the Mediterranean f r u i t f l y ( C e r a t i t i s c a p i t a t a (Wiedemann)),the melon f l y (Dacus c u c u r b i t a e G o q u i l l e t ) , and the o r i e n t a l f r u i t f l y (Dacus d o r s a l i s Hendel) (2). This e a r l y warning system, i n use s i n c e the l a t e f i f t i e s , has saved the USDA m i l l i o n s of d o l l a r s i n p o t e n t i a l e r a d i c a t i o n costs by d e t e c t i n g i n c i p i e n t i n f e s t a t i o n s of the

7.

BEROZA

Control of the Gypsy Moth

101

p e s t s , and, on q u i t e a few occasions, q u i c k l y wiping them out bef o r e they could spread. Now, however, researchers working w i t h pheromones have begun t o r e a l i z e that the a v a i l a b i l i t y of a pheromone i s only t h e f i r s t step i n u t i l i z a t i o n of these chemicals f o r pest c o n t r o l . J u s t as the pheromones f o r d i f f e r e n t i n s e c t species are d i f f erent, so are the responses of the i n s e c t s l i k e l y t o d i f f e r from species t o species. Thus, f o r e f f i c i e n t use of these m a t e r i a l s , the methods o f u t i l i z a t i o n must be b u i l t around the b e h a v i o r a l patterns of each s p e c i e s . Knowledge o f the behavior of each species under the c o n d i t i o n s o f pheromone use i s t h e r e f o r e j u s t as necessary as knowledge of the p r o p e r t i e s o f the chemical i t s e l f , and considerable experimentation may be r e q u i r e d t o achieve optimum performance of the pheromone a g a i n s t a given s p e c i e s . To i l l u s t r a t e , some parameters that must be considered when traps are to be used i n d e t e c t i o n and survey of a s p e c i f i c species i n c l u d e t r a p design, trap h e i g h t , trap placement, t r a p d u r a b i l i t y , type of b a i t dispenser and i t s p o s i t i o n i n the t r a p , trapping means (e.g. adhesive, i n s e c t i c i d e ) , emission r a t e o f the l u r e , l u r e s t a b i l i t y and q u a n t i t y , d u r a t i o n of e f f e c t i v e n e s s , r a t i o o f the i n g r e d i e n t s i f the l u r e i s multicomponent, e f f e c t of aging of the l u r e , e f f e c t of host crop, e f f e c t i v e d i s t a n c e of a t t r a c t i o n , time of i n s e c t response, cost of the t r a p , and, perhaps u l t i m a t e l y , the r e l a t i o n s h i p between t r a p catch and number of i n s e c t s i n the v i c i n i t y of the t r a p . Some of these v a r i a b l e s are c r i t i c a l enough t o make the d i f f e r e n c e between success and f a i l u r e . For example, gypsy moth traps t e s t e d a t heights up t o 4 m caught best between ground l e v e l and 2 m (3) : traps of the o r i e n t a l f r u i t moth (Grapholitha molesta (Busck)) t e s t e d s i m i l a r l y caught almost no moths a t ground l e v e l , caught best a t a height of 1 m, somewhat l e s s a t 2 m, and few a t 3 m (4). With the pecan bud moth (Gretchena b o l l i a n a ( S l i n g e r l a n d ) ) , which responds t o the o r i e n t a l f r u i t moth pheromone and i s found i n the same v i c i n i t y but on a d i f f e r e n t h o s t , t r a p captures were again very low near ground l e v e l (1.5 m) but increased prog r e s s i v e l y as trap heights were increased t o 9.1 m, the g r e a t e s t height t e s t e d (5). L i k e w i s e , s u b t l e d i f f e r e n c e s i n chemical composition o f a pheromone were shown to a f f e c t the mean captures of the o r i e n t a l f r u i t moth; captures v a r i e d from l e s s than one t o 109 per trap when the ^-isomer content o f (Z^-8-dodecenyl acetate was changed from 0 t o 20%; the optimum catch occurred w i t h about 6% 12 isomer ( 6 ) . Oddly enough, w i t h the sympatric pecan bud moth, the same 0 t o 20% v a r i a t i o n of JE-isomer content i n the same compound caused no a p p r e c i a b l e d i f f e r e n c e i n catch (Table I) (7). Unquestionably, more a t t e n t i o n must be devoted t o the study o f such trap parameters i f the e r r a t i c r e s u l t s sometimes reported by e a r l y i n v e s t i g a t o r s are to be avoided.

PEST M A N A G E M E N T

102

WITH

INSECT SEX

ATTRACTANTS

Table I . E f f e c t of IS isomer i n (Z)-8-dodecenyl acetate on captures of male o r i e n t a l f r u i t moths and pecan bud moths i n b a i t e d traps (7) . Mean no. of males captured per trap % Ε isomer 0 2 5 7.5 10 20

O r i e n t a l f r u i t moth 1.5 36.0 108.8 27.3 5.7 0.33

a cd e bed ab a

Pecan budmoth 253.8 226.3 215.8 241.3 251.5 244.3

a a a a a a

a/ Means f o l l o w e d by the same l e t t e r are not s i g n i f i c a n t l y d i f f ­ erent at the 5% l e v e l of confidence based on Duncan's m u l t i p l e range t e s t . As an aside and by way of r a t i o n a l i z a t i o n , i t i s l i k e l y t h a t the many d i f f e r e n c e s i n the response of species help maintain the reproductive i s o l a t i o n of species i n nature, p a r t i c u l a r l y of those l o c a t e d i n the same v i c i n i t y at the same time. When a l l of the t r a p parameters are optimized, r e s u l t s can be g r a t i f y i n g . Thus, Gentry et a l . reported a recapture r a t e of 69% f o r 1000 marked o r i e n t a l f r u i t moth males that he r e l e a s e d i n a 2-acre orchard c o n t a i n i n g 5 traps (8) of a design and at a height found best i n previous s t u d i e s (4). The b a i t dispenser, because i t c o n t r o l s the r e l e a s e of the pheromone, may be considered the heart of a t r a p . The i d e a l dispenser should emit l u r e at a constant r a t e , p r e f e r a b l y the optimum r a t e f o r a t t r a c t i o n , over a prolonged p e r i o d and h o p e f u l l y f o r an e n t i r e season. N o n v o l a t i l e d i l u e n t s , c a l l e d keepers ( 9 ) , m i n e r a l s , p l a s t i c caps and m a t r i c e s , and other m a t e r i a l s and de­ v i c e s (e.g. 10-13) have been used to slow the v o l a t i l i z a t i o n of pheromones and thereby extend d u r a t i o n of e f f e c t i v e n e s s . Rec e n t l y , a 3-layer p l a s t i c laminate, c a l l e d a Hereon ® dispenser — , was found to approach i d e a l performance f o r extended but l i m i t e d periods of time (14). The pheromone, which i s concentrated i n the i n s i d e l a y e r of the laminate, g r a d u a l l y d i f f u s e s out through the outer p l a s t i c l a y e r s , and r e g u l a t i o n of emission i s r e a d i l y achieved by v a r y i n g the t h i c k n e s s of the laminate and the area exposed. As a f u r t h e r consequence of i t s l o c a t i o n i n the i n n e r l a y e r , the pheromone i s p r o t e c t e d from degradation by o x i d a t i o n , h y d r o l y s i s , and l i g h t . The value of t h i s p r o t e c t i v e e f f e c t should not be underestimated because degradation products are o f t e n potent i n h i b i t o r s of a t t r a c t i o n ; e.g. many pheromones are 1/ Mention of a p r o p r i e t a r y product does not imply endorsement by the USDA.

7.

BEROZA

Control of the Gypsy Moth

103

a c e t a t e s , and a number of the a l c o h o l s that form on d e a c e t y l a t i o n proved to be powerful i n h i b i t o r s of the a t t r a c t i o n o f the pheromone even when they are present t o the extent o f only a few percent (4). The prolonging of a c t i v i t y of unstable aldehyde pheromones has been e s p e c i a l l y noteworthy. Good r e s u l t s w i t h the Hereon laminate have now been obtained w i t h a number of pheromones, e.g., those o f the gypsy moth, b o l l w e e v i l (Anthonomus grandis Boheman), tobacco budworro ( H e l i o t h i s v i r e s c e n s ( F a b r i c i u s ) ) , pink bollworm (Pectinophora g o s s y p i e l l a (Saunders)), cabbage looper '{Trichoplusia n i (Hubner)), l e s s e r peach t r e e borer (Synanthedon p i c t i p e s (Grote and Robinson)), peach t r e e borer (Sanninoidea e x i t i o s a (Say)), and bark b e e t l e s . Mass Trapping. Traps may a l s o be of value i n the d i r e c t c o n t r o l of i n s e c t p e s t s , e.g., f o r mass t r a p p i n g of males bef o r e they can l o c a t e females f o r mating. However, the traps a r e apt to be u s e f u l only when i n f e s t a t i o n s are very l i g h t , s i t u a t i o n s i n which the r a t i o o f traps t o i n s e c t s can be h i g h enough t o prevent the p o p u l a t i o n o f i n s e c t s from growing (15, 16). However, a high p o p u l a t i o n can be reduced t o a low l e v e l w i t h an i n s e c t i c i d e (or by other means), and the traps may then be capable i n themselves (without f u r t h e r use of i n s e c t i c i d e ) of preventing a p o p u l a t i o n b u i l d u p . Recent t r i a l s have already shown t h a t the mass-trapping approach i s v a l i d against l o w - l e v e l i n s e c t popul a t i o n s (17, 18). An important t h e o r e t i c a l advantage o f mass t r a p p i n g i s i t s greater e f f i c i e n c y as the p o p u l a t i o n diminishes — t o the p o i n t that i t u l t i m a t e l y might be capable o f e r a d i c a t i n g a t a r g e t species (16). This p o s s i b i l i t y focuses a t t e n t i o n on the need f o r more e f f i c i e n t t r a p p i n g devices and b a i t dispensers. Toward t h i s end, the a l r e a d y - c i t e d parameters needing a t t e n t i o n i n traps f o r survey and d e t e c t i o n are l i k e l y to be important i n traps used f o r c o n t r o l . A d d i t i o n a l c o n s i d e r a t i o n s are t r a p c a p a c i t y , t r a p d e n s i t y (no./hectare) and d i s t r i b u t i o n , and method of deployment. D i s r u p t i o n of Pheromone-Guidance System of I n s e c t s . I n 1960, the suggestion was made t h a t i n s e c t sex pheromones could be r e l e a s e d i n t o the atmosphere (from s m a l l pheromone-containing p a r t i c l e s ) t o confuse male i n s e c t s seeking females f o r mating, and t h a t i n t h i s way the r e p r o d u c t i o n of i n s e c t pests could be reduced (19). I n other words, i f s y n t h e t i c pheromone were emitted from many dispersed p a r t i c l e s , the males would be unable to d i s t i n g u i s h between the odor o f the s y n t h e t i c and that the females generate t o lead the males t o them; the males would then not be able t o f i n d the females. This approach has s p e c i a l appeal i n that the r e p r o d u c t i o n o f the i n s e c t pest would be suppressed w i t h an innocuous chemical, and the a c t i o n of t h e l u r e would have no e f f e c t on the environment o r on any but the offending s p e c i e s . ( T o x i c o l o g i c a l data on d i s p a r l u r e , the gypsy moth sex pheromone, and on 8 other b e h a v i o r - c o n t r o l l i n g chemicals

104

PEST

MANAGEMENT WITH

INSECT SEX

ATTRACTANTS

i n d i c a t e t h a t these chemicals have a very low order of t o x i c i t y (20)). Such an approach to c o n t r o l the gypsy moth was f u r t h e r favored because of the e x t r a o r d i n a r y potency of d i s p a r l u r e (1 ng s u i t a b l y formulated w i t h a keeper remained e f f e c t i v e f o r 3 months i n the f i e l d ( 9 ) ) , the a b i l i t y of the traps to monitor e f f i c i e n t l y the whereabouts of the i n s e c t , the low cost of the s y n t h e t i c l u r e (compared w i t h most pheromones), the p o t e n t i a l a v a i l a b i l i t y of the l u r e i n l a r g e amount (1200 pounds were purchased i n 1975), and the p o s s i b i l i t y of h a l t i n g the spread of the gypsy moth from the p r e s e n t l y i n f e s t e d Northeastern United States to the r e s t of the country. As w i t h mass t r a p p i n g , the air-permeation or "confusion" approach t h e o r e t i c a l l y becomes more e f f i c i e n t as the moth popul a t i o n d e c l i n e s (15). A c c o r d i n g l y , the p o p u l a t i o n must be low for maximum or even adequate e f f e c t i v e n e s s ; otherwise, males may f i n d females by chance, a p o s s i b i l i t y that increases w i t h i n creasing abundance of moths i n a given searching area. Formulation Research We know now that the amounts of d i s p a r l u r e we used i n i t i a l l y i n our attempts to confuse the i n s e c t ( a c t u a l l y only 50 mg/hectare) were much too low. However, even i n these t e s t s , we d i d d i s o r i e n t mate-seeking of males f o r as much as 3 weeks (21). We recognized that a s u i t a b l e f o r m u l a t i o n had t o be devised t o demonstrate such d i s o r i e n t a t i o n f o r an e n t i r e season w i t h s u f f i c i e n t lead time t o allow f o r l u r e a p p l i c a t i o n (about 6-8 weeks), and because the area t o be t r e a t e d f o r gypsy moth i s p o t e n t i a l l y enormous, we s e t t l e d on a e r i a l d i s t r i b u t i o n of the confusant as the most f e a s i b l e means of a p p l i c a t i o n . Laboratory t e s t s were conducted i n i t i a l l y on formulations w i t h a great v a r i e t y of m a t e r i a l s , and these t e s t s were f o l l o w e d by f i e l d t r i a l s w i t h l a b o r a t o r y - r e a r e d i n s e c t s on 16-hectare p l o t s to evaluate the performance of the most promising candidates. These t e s t s were conducted out of season by our USDA APHIS l a b o r a t o r y a t O t i s A i r Force Base, Mass. t o avoid i n t e r f e r e n c e s that might occur during the season when unknown numbers of n a t i v e i n sects would be i n or near the t e s t s i t e s . A treatment was cons i d e r e d e f f e c t i v e i f a h i g h p r o p o r t i o n of the males released i n the t r e a t e d area was unable to f i n d monitor traps b a i t e d w i t h d i s p a r l u r e or females. Captures i n t r e a t e d areas were always compared w i t h those i n untreated ones. Tests were made w i t h d i s p a r l u r e on or i n hydrophobic paper, cork, molecular s i e v e s , and microcapsules. The microcapsules, which were s u p p l i e d o r i g i n a l l y as a water s l u r r y c o n t a i n i n g about 30% microcapsules, turned out to be the most promising of the f o r m u l a t i o n s , and two types were evaluated f u r t h e r . One had a g e l a t i n e - b a s e w a l l that was p l a s t i c coated, and the other had a nylon-based w a l l . Contracts were l e t w i t h the manufacturers of the microcapsules to produce a v a r i e t y of

7.

BEROZA

Control of the Gypsy Moth

105

these m a t e r i a l s , which were then t e s t e d i n our B e l t s v i l l e l a b oratory t o determine t h e i r r a t e s o f l u r e emission over prolonged periods. Some of the microcapsule parameters t h a t were v a r i e d were diameter o f the microcapsule, t h i c k n e s s of the capsule w a l l , solvent i n the capsules and c o n c e n t r a t i o n o f d i s p a r l u r e t h e r e i n , degree o f c r o s s l i n k i n g of the p l a s t i c w a l l , and amount o f p l a s t i c coating on the capsule. Laboratory Tests. Even though the t e s t i n g of pheromone formul a t i o n s i n the f i e l d , say as confusants, provides b a s i c data concerning performance, complete r e l i a n c e on f i e l d t e s t i n g i s imp r a c t i c a l . Formulations g e n e r a l l y r e q u i r e many changes i n the course o f development, a n d , f i e l d t e s t s t o check each change would be p r o h i b i t i v e l y expensive and time-consuming, e s p e c i a l l y when such t e s t s are l i m i t e d t o c e r t a i n seasons and/or must be made over a l a r g e area, e.g., w i t h f l y i n g i n s e c t s . More a p p r o p r i a t e l y , l a b o r a t o r y procedures can be u t i l i z e d t o determine the emission r a t e s o f pheromones (or s i m i l a r b e h a v i o r - c o n t r o l l i n g chemicals) from slow-release formulations a t c o n d i t i o n s approximating those encountered i n the f i e l d ; then these data can be compared and c o r r e l a t e d w i t h the r e s u l t s obtained i n the f i e l d . For example, i f a f o r m u l a t i o n performs w e l l i n the f i e l d f o r 2 weeks b u t poorly f o r the next 2 weeks, i t s performance i n the l a b o r a t o r y can be c h a r a c t e r i z e d by p e r i o d i c measurement o f emission of l u r e at given c o n d i t i o n s . The performance i s then compared i n the l a b o r a t o r y w i t h t h a t of others a t i d e n t i c a l c o n d i t i o n s , and those p r o v i d i n g adequate l u r e emission f o r longer periods can then be s e l e c t e d f o r f i e l d t e s t i n g . A l s o , the e f f e c t o f each change i n f o r m u l a t i o n , e.g., a d d i t i o n o r removal of an i n g r e d i e n t , on pheromonal emission and p e r s i s t e n c e can be determined i n the l a b o r a t o r y , and i n g r e d i e n t s can be s e l e c t e d t o provide optimum performance. Since the r a t e o f emission o f the pheromone i s probably the s i n g l e most important parameter governing the performance of a pheromone dispenser i n a t r a p or a confusant broadcast on f o l i a g e i n the f i e l d , the great value o f the emission r a t e s determined i n the l a b o r a t o r y under c o n t r o l l e d c o n d i t i o n s can be r e a d i l y appreciated. In some of our e a r l y work, we t r i e d t o determine emission r a t e s by p e r i o d i c a n a l y s i s o f the amount o f pheromone remaining i n samples. A l a r g e s e r i e s o f i d e n t i c a l l y made samples had t o be prepared because samples were destroyed i n the a n a l y s i s . We found t h i s procedure u n r e l i a b l e because the pheromone l o s t on aging o f t e n had not a l l v o l a t i l i z e d ; i n s t e a d , some was l o s t by degradation, so the emission r a t e s found were i n c o r r e c t . F a r b e t t e r r e s u l t s were obtained by d i r e c t measurement of the pheromone taken up by a i r passed over the sample a t a f i x e d r a t e . Since the sample was not destroyed i n the a n a l y s i s , the emission r a t e could be determined on the same sample f o r the d u r a t i o n o f aging. I n essence, f a r fewer samples were r e q u i r e d f o r the

106

PEST

MANAGEMENT

WITH

INSECT

SEX

ATTRACTANTS

emission s t u d i e s , and r e s u l t s were much more r e l i a b l e . A simple device used to c o l l e c t v o l a t i l e s from pheromone dispensers ( u s u a l l y from t r a p s ) i s shown i n F i g u r e 1 (22). A i r at 100 ml/min. and at a constant temperature i s passed through a s i n t e r e d g l a s s gas d i s p e r s i o n tube i n t o a g l a s s tube con­ t a i n i n g the pheromone dispenser. The a i r p i c k s up the vapors and c a r r i e s them v i a an adaptor i n t o a s o l v e n t contained i n a c e n t r i f u g e tube. With d i s p a r l u r e d i s p e n s e r s , a 4-hour c o l l e c ­ t i o n p e r i o d was u s u a l l y necessary to o b t a i n enough l u r e f o r a good a n a l y s i s . A f t e r such a c o l l e c t i o n , the adaptor i s washed w i t h s o l v e n t (and the washings added to the c o l l e c t i o n s o l v e n t ) to completely r e t r i e v e the v o l a t i l i z e d pheromone. The combined s o l v e n t and washings are concentrated, an a l i q u o t i s analyzed by gas chromatography, and the emission r a t e i s c a l ­ c u l a t e d i n micrograms of l u r e emitted per hour. F i g u r e 2 shows a more complex device used to c o l l e c t the emission of pheromones from confusant formulations spread on planchets 5 cm i n diameter (22). A weighed sample (0,5 g) of wet microcapsules (residue from f i l t r a t i o n of the aqueous s l u r r y ) i s c a r e f u l l y dispersed w i t h water on the planchets and then allowed to dry at room temperature f o r a day. Emission of pheromone from the microcapsules i s then determined p e r i o d ­ i c a l l y , a f t e r aging at f i x e d c o n d i t i o n s , by passing 100 ml of a i r / m i n . at a constant temperature over the microcapsules and c o l l e c t i n g the vapors i n a s o l v e n t . Operation of the apparatus i s described i n the legend of F i g u r e 2. The inner surfaces of the p e t r i d i s h Ν and the adaptor 0_ must be washed c a r e f u l l y w i t h s o l v e n t to c o l l e c t a l l the v o l a t i l i z e d phero­ mone; as b e f o r e , the washings are added to the c o l l e c t i o n s o l v e n t , and gas chromatographic analyses are made on the con­ centrated s o l v e n t . The samples i n the planchets may be aged by exposure i n a constant-temperature room. To speed our work, we used a s p e c i a l apparatus that a c c e l e r a t e d the aging pro­ cess and allowed 9 planchets to be aged at almost i d e n t i c a l c o n d i t i o n s so the emission r a t e s c o u l d be compared (22). We included a known f o r m u l a t i o n ( u s u a l l y our best one) and de­ termined emission r a t e s r e l a t i v e to i t . I n other words, we determined r e l a t i v e emission r a t e s , not absolute ones. I n a d d i t i o n to the f o r e g o i n g , we sent important f r e s h and aged samples to our b i o l o g i c a l l a b o r a t o r y a t O t i s A i r Force Base f o r bioassay to v e r i f y our chemical f i n d i n g s , i . e . , h i g h emiss­ i o n r a t e s of l u r e should c o i n c i d e w i t h h i g h b i o l o g i c a l a c t i v i t y , and v i c e v e r s a . We a l s o compared formulations of gypsy moth confusant by a p p l y i n g them d i r e c t l y onto oak leaves (a favored food) and then i n s e r t i n g the coated leaves i n t o the apparatus of F i g u r e 1 f o r c o l l e c t i o n and measurement of the d i s p a r l u r e emitted. Determinations were made p e r i o d i c a l l y over a p e r i o d of s e v e r a l months. At the same time, other leaves coated i d e n t i c a l l y were evaluated b i o l o g i c a l l y by exposing them i n traps to male moths e i t h e r i n a bioassay chamber or i n the

/ the Gypsy Moth

Oh j j ~n υI j I Lil_

107

Figure 1. Emission collection from pheromone wicks. Air (100 ml/min) which enters glass tube V via gas dispersion tube W held by rubber stopper X, passes over sample Y and out through adapter Z, exiting through solvent in 12ml centrifuge tube U (22). y

Figure 2. Emission collection from planchets. Above is top view of petri dish Ν with arrows showing air entering (100 ml/mm) via 2 glass tubes (5-mm OD) and leaving via exit tube O; planchet I is held within. Bottom is side view of petri dish Ν mounted on rubber -H- dam P, polyurethane foam sheet Q, and table R of lab jack. Weight S (water-containing jar) rests on rubber y pad T, which presses on petri dish and prevents pass­ ing air from escaping from bottom edge of petri dish. \ Air, which leaves via exit tube O, passes through sol\ vent in 12-ml centrifuge tube V. Drawn to scale (diam U of planchet is5 cm) (22).

108

PEST

MANAGEMENT

WITH

I N S E C T SEX

ATTRACTANTS

f i e l d . The number of males caught w i t h each f o r m u l a t i o n was considered a measure of a t t r a c t i o n and very l i k e l y of d i s ­ p a r l u r e emission. Of course, i f i n h i b i t o r s of a t t r a c t i o n were formed on aging, the chemical and b i o l o g i c a l t e s t s would not agree, and we would be a l e r t e d to t h i s d i f f i c u l t y . Since n a t u r a l growth of the l e a f and wind, r a i n , and other c l i m a t i c f a c t o r s would tend to remove the confusant micro­ capsules (or other such p a r t i c l e s ) from the leaves to which they were a p p l i e d , a s t i c k e r was added to the formulations to assure adhesion of the p a r t i c l e s to the leaves f o r the necessary i n t e r v a l . The s t i c k e r s t r i e d were w a t e r - d i s p e r s i b l e , which once d r i e d ( g e n e r a l l y l e s s than 2 hours a f t e r a p p l i c a t i o n ) were not again dispersed by water (or r a i n or h i g h h u m i d i t y ) . S t i c k e r s were t e s t e d by adding them to each f o r m u l a t i o n ( i n s e v e r a l c o n c e n t r a t i o n s ) , a p p l y i n g the combinations to oak leaves, a l l o w i n g 1 to 2 hours f o r d r y i n g , s p r a y i n g the leaves w i t h a stream of water from a wash b o t t l e , and then i n s p e c t i n g the leaves to determine the extent to which the confusant p a r t i c l e s were removed by the a c t i o n of the water. For formula­ t i o n s adjudged s u f f i c i e n t l y adhering, the coated leaves were aged and p e r i o d i c a l l y sprayed w i t h the water stream to d e t e r ­ mine whether the confusant p e r s i s t e d . ( L i v i n g leaves of oak seedlings were used f o r long aging periods.) I n t h i s way, the s t i c k e r s were evaluated i n terms of time r e q u i r e d f o r d r y i n g and degree of adhesion over the d e s i r e d i n t e r v a l . Coated leaves were a l s o soaked i n water f o r s e v e r a l hours (to simulate exposure to r a i n ) and subjected to the a c t i o n of the water stream to check adhesion of the confusant p a r t i c l e s . The method of a p p l i c a t i o n of confusant was determined from the type of f o r m u l a t i o n used. One of our e a r l i e s t f i e l d t r i a l s was made w i t h a e r i a l l y d i s p e r s e d d i s p a r l u r e - c o a t e d cork granules, which were t e s t e d w i t h and without a s t i c k e r . The s t i c k e r i n s o l u t i o n form was sprayed onto the dry cork granules as they emerged from the a i r c r a f t . The cork formula­ t i o n w i t h no s t i c k e r f a i l e d a f t e r the f i r s t r a i n ; the formula­ t i o n w i t h s t i c k e r performed w e l l f o r at l e a s t 6 weeks d e s p i t e some very heavy r a i n s (18). This r e s u l t h i g h l i g h t s the im­ portance of a good s t i c k e r . The microcapsule water s l u r r i e s p r e s e n t l y used are a p p l i e d from a i r c r a f t w i t h c o n v e n t i o n a l spray equipment. Since these capsules are l i g h t e r than water and tend to separate on standing, a t h i c k e n e r was added, and the suspension was s t i r r e d during the spraying o p e r a t i o n to d i s p e r s e the microcapsules u n i f o r m l y i n the aqueous phase (18). A t y p i c a l f o r m u l a t i o n of the microcapsules c o n s i s t e d of the f o l l o w i n g i n g r e d i e n t s : 17.6% capsules (25-200 μ diam., 10% g e l a t i n e - b a s e w a l l , 1/4-coated w i t h p l a s t i c ) c o n t a i n i n g 2.2% d i s p a r l u r e i n xylene or 1:3 amyl acetate-xylene, s u p p l i e d by N a t i o n a l Cash R e g i s t e r Company, Dayton, Ohio as a 30% aqueous s l u r r y .

7.

BEROZA

Control of the Gypsy Moth

109

2% UCAR l a t e x 680. 29% o f 1% hydroxyethyl c e l l u l o s e ( S o i l s e r v e , I n c . , Salinas, C a l i f . ) . 1.7% o f 1% aqueous potassium hydroxide. 49.7% water. For a p p l i c a t i o n of 2 g d i s p a r l u r e / a c r e (5 g l u r e / h e c t a r e ) , 575 ml/acre of the above f o r m u l a t i o n was a p p l i e d . A s i m i l a r nylon-base capsular f o r m u l a t i o n was s u p p l i e d by Pennwalt Corp., King o f P r u s s i a , Pa. (18). The formulations were sprayed from Spraying Systems No. 8010 t i p s on spray boom n o z z l e s . S u b s t a n t i a l l o s s e s o f spray may occur from a i r c r a f t , and much depends upon the c o n d i t i o n s of treatment. F l i g h t s must be made i n calm a i r t o avoid excessive d r i f t o f spray from the t a r g e t area. The a i r c r a f t must f l y c l o s e t o the t r e e tops (about 20 m above the f o r e s t canopy) so the spray s t r i k e s the f o l i a g e w h i l e i t i s s t i l l wet. ( I t i s presumed t h a t formulat i o n d r o p l e t s w i l l dry e x c e s s i v e l y i n f a l l i n g from great h e i g h t s and then w i l l be l e s s l i k e l y t o adhere t o the f o l i a g e . ) R a i n o c c u r r i n g before the spray can dry f u l l y ( w i t h i n 2 hours a f t e r spraying) may remove much o f the confusant from the f o l i a g e . In g e n e r a l , the percentage o f spray l a n d i n g on t a r g e t i s f a r l e s s from a i r c r a f t than from ground equipment, so allowances must be made f o r some l o s s e s of spray i n a i r c r a f t a p p l i c a t i o n s . I t i s even conceivable t h a t the best f o r m u l a t i o n could be rendered i n e f f e c t i v e by an improper a p p l i c a t i o n . Large F i e l d T r i a l s t o Prevent Gypsy Moth Mating At t h i s p o i n t , some i n f o r m a t i o n on the gypsy moth i s appropriate. The i n s e c t i s a s e r i o u s pest of f o r e s t , shade, and orchard t r e e s i n Europe and the Northeastern United S t a t e s . About e a r l y May l a r v a e emerge from eggs l a i d the previous summer and proceed t o consume the leaves of t h e i r favored h o s t s ; t r e e s are u l t i m a t e l y d e f o l i a t e d and k i l l e d by heavy i n f e s t a t i o n s . When f u l l y grown, the l a r v a e pupate. They emerge as adult moths some time i n J u l y or e a r l y August depending on the l o c a l c l i m a t e . The male, a strong f l i e r , seeks out the n o n - f l y i n g female, being guided t o h e r by the w i n d - c a r r i e d scent or sex pheromone she emits. The male mates w i t h the female, she l a y s some 300-800 eggs i n a mass, and another generation of the i n s e c t i s on i t s way. F o l l o w i n g the i d e n t i f i c a t i o n and s y n t h e s i s of the gypsy moth sex pheromone i n 1970 (J23), s m a l l f i e l d t r i a l s , u s u a l l y on 16-hectare p l o t s , were conducted (by USDA and by the Pennsylvania State U n i v e r s i t y ) t o evaluate new formulations and techniques f o r the d i r e c t c o n t r o l of the gypsy moth. R e s u l t s obtained w i t h the microencapsulated confusant formulations i n 1971 and 1972 were promising enough t o j u s t i f y a g r e a t l y expanded t r i a l i n a n a t u r a l i n f e s t a t i o n i n 1973.

110

PEST

MANAGEMENT

WITH

INSECT

SEX

ATTRACTANTS

The 1973 t e s t was conducted i n Massachusetts by the Massachusetts Department of N a t u r a l Resources i n c o o p e r a t i o n w i t h the U n i v e r s i t y of Maine and the USDA (24^. The area t r e a t e d was d e l i b e r a t e l y l a r g e — about 60 km or 24 mi. — i n order to approach and evaluate p r a c t i c a l c o n d i t i o n s of opera­ t i o n and a l s o t o minimize any "edge e f f e c t s " that might r e s u l t from the i n c u r s i o n of males i n t o the d i s p a r l u r e - t r e a t e d areas during the moth f l i g h t season. On J u l y 6-10, j u s t b e f o r e the a n t i c i p a t e d moth emergence, the f o r m u l a t i o n d e s c r i b e d i n the previous s e c t i o n (with xylene as the e n c a p s u l a t i n g s o l v e n t ) was a p p l i e d by three a i r c r a f t at a r a t e of 5 g d i s p a r l u r e / h e c t a r e . Another area of s i z e s i m i l a r to the t r e a t e d area was l e f t un­ t r e a t e d to serve as a c o n t r o l . I n both areas, one hundred 0.1-hectare (0.25-acre) p l o t s , s u i t a b l y d i s t r i b u t e d , were monitored as f o l l o w s : e a r l y s p r i n g b e f o r e f o l i a t i o n of the t r e e s , egg-mass counts were made. J u l y d August (post-treatment) counts were made of moths captured by traps ( 2 / p l o t ) each b a i t e d w i t h a c o t t o n wick c o n t a i n i n g 10 μ g d i s p a r l u r e p l u s 2 mg t r i o c t a n o i n as keeper (which approximates a female i n a t t r a c t i o n ) and by traps (2/ p l o t ) each b a i t e d w i t h a female. In a d d i t i o n , f e r t i l i z a t i o n of untethered females ( 2 / p l o t ) exposed on t r e e trunks (Figure 3) was determined. Females i n the traps and exposed on t r e e trunks were r e p l a c e d every t h i r d day. I n October and November, egg-mass counts were again made. I n the untreated area, the d i s p a r l u r e traps caught 2193 males; only 63 males were taken i n the t r e a t e d area. The de­ crease i n captures was more than 97%. R e s u l t s were even more s t r i k i n g w i t h the female-baited t r a p s . A t o t a l of 1136 males were captured i n the untreated a r e a , and o n l y 1 was caught i n the t r e a t e d area. The trap captures are shown g r a p h i c a l l y i n F i g u r e 4 f o r the e n t i r e season. Undoubtedly, the odor-guidance system of the moth was s e r i o u s l y impaired by the d i s p a r l u r e treatment. F i g u r e 5 shows the percentages of the untethered females that were found f e r t i l i z e d i n the t r e a t e d and untreated areas during the p e r i o d immediately a f t e r treatment w i t h d i s p a r l u r e to the end of the moth f l i g h t season.For 2 1/2 weeks a f t e r t r e a t ­ ment, mating of recovered females i n the t r e a t e d area remained low even though most of the time 95-100% of the females i n the c o n t r o l area were mated. Subsequently, the percentage mated i n the t r e a t e d area climbed t o h i g h l e v e l s f o r 11 days though i t then f e l l to about 56% during the l a s t week of the t e s t (which shows that the microcapsules were s t i l l e x e r t i n g an e f f e c t at 5 weeks post-treatment). Thus, d e s p i t e the apparent d i s r u p t i o n of the odor-guidance system of the i n s e c t s i n d i c a t e d by the g r e a t l y decreased t r a p catches throughout the f l i g h t season (Figure 4 ) , males were probably numerous enough i n the t r e a t e d area t o l o c a t e females by chance. Ι η

I n

a n

7.

BEROZA

111

Control of the Gypsy Moth

Figure 3. Placement of untethered female moth used in determining rate of fertilization in areas treated and not treated with disparlure micro­ capsules.

0.08 0.060.04 0.02 0.00

r «""ι ' ι ' ι • ι ' ι • > ' »

1

'

CAPTURES OF MALE GYPSY

MOTHS

UNTREATED £ TRAPS

J

AREA

LURE TRAPS

Λ

TREATED AREA L U R E TRAPS

5

9

13

A U G U S T Figure 4. Captures of male gypsy moths by lure- and female-baited traps in untreated area and in area treated July 6-10 by application of microencapsulated disparlure at the rate of 5 g disparlure/ha. Upper graph shows captures by lure traps in treated area on a 10-fold expanded scale, (24).

112

PEST

MANAGEMENT

WITH

INSECT SEX

ATTRACTANTS

However, the p r e - and post-season egg-mass counts showed that the treatment d i d prevent a s i g n i f i c a n t b u i l d u p of the moth p o p u l a t i o n . These counts were not s i g n i f i c a n t l y d i f f e r e n t i n the t r e a t e d p l o t s (though post-season counts were 1.4-1.6 times the pre-season v a l u e s ) , but i n the u n t r e a t e d p l o t s , postseason counts were 3 t o 3 1/2 times the pre-season counts, a significant difference. In 1974, t r i a l s s i m i l a r t o those of 1973 were again undertaken (by the same groups) i n a n a t u r a l i n f e s t a t i o n i n the same g e n e r a l v i c i n i t y of Massachusetts (25). Data were sought on a) the r e l a t i v e e f f e c t of doses of l u r e g r e a t e r than those a p p l i e d i n 1973, b) the f e a s i b i l i t y of reducing a h i g h l e v e l p o p u l a t i o n of gypsy moth l a r v a e w i t h i n s e c t i c i d e before d i s p a r l u r e was a p p l i e d during the mating f l i g h t , c) the e f f e c t i v e ness of mass t r a p p i n g w i t h high-potency traps (Figure 6) and d) the v a l u e of high-potency t r a p s f o r m o n i t o r i n g d i s p a r l u r e t r e a t e d areas (Figure 7 ) . The same microencapsulated formulat i o n of d i s p a r l u r e (except that the s o l v e n t i n the capsules was 1:3 amyl acetate-xylene) was used. The t r a p s used i n mass trapping and i n monitoring were b a i t e d w i t h high-potency p l a s t i c laminates c o n t a i n i n g 16 and 8 mg d i s p a r l u r e / t r a p , r e s p e c t i v e l y ; Tack-trap ® adhesive was used to capture responding i n s e c t s . The dosage t e s t s c o n s i s t e d of 1) one treatment of 5 g d i s par l u r e / h e c t a r e as i n 1973, 2) two treatments of 10 g l u r e / hectare 2 1/2 weeks a p a r t , and 3) one treatment of 20 g l u r e / hectare. The treatment w i t h 5 g l u r e / h e c t a r e gave d e f i n i t e though l e s s than adequate suppression: mating success of exposed females was reduced 47% compared w i t h the c o n t r o l , and both male t r a p captures and post-treatment egg-mass counts i n d i c a t e d about 50% c o n t r o l . The h i g h e r dosages were h i g h l y e f f e c t i v e : mating success of the untethered females was r e duced 94-97%, and male captures and post-treatment egg-mass counts were l i k e w i s e markedly suppressed. I n essence then, the dosage t e s t s e s t a b l i s h e d t h a t 20 g l u r e / h e c t a r e (8 g l u r e / a c r e ) were enough to suppress d r a s t i c a l l y the l o w - l e v e l moth p o p u l a t i o n (from 10-15 egg-masses/hectare pre-season). The t e s t to reduce a p o t e n t i a l l y h i g h - l e v e l p o p u l a t i o n to a low l e v e l before d i s p a r l u r e treatment was conducted on two i s l a n d s (one i s l a n d being the c o n t r o l ) i n the Quabbin R e s e r v o i r to minimize any i n f l u x of male moths from a d j o i n i n g t e r r i t o r y . I t turned out that the i n s e c t i c i d e a p p l i e d t o t h e 6-km t r e a t e d i s l a n d (two a p p l i c a t i o n of c a r b a r y l as Sevin® 4 - o i l a t 1.14 kg A l / h e c t a r e 11 days apart) depressed the moth p o p u l a t i o n t o too low a l e v e l , and the females found mated and the post-season egg-mass counts were simply too low to e s t a b l i s h s i g n i f i c a n t d i f f e r e n c e s among the f o l l o w i n g three treatments that were superimposed on the i n s e c t i c i d e treatment: 1) 20 g l u r e / h e c t a r e as microcapsules, 2) mass t r a p p i n g w i t h 25 high-potency t r a p s / h e c t a r e , and 3) no treatment. The three treatments a l l showed the same degree of mating by the exposed females, 2.4-3.2% 2

7.

BEROZA

Control of the Gypsy Moth

P E R C E N T

JULY Figure 5. Percentage of recovered female and untreated areas. The relative percent the graph for the different periods of the 12 (indicated by breaks

113

M A T E D

AUGUST

gypsy moths found fertilized in the treated mated (treated/untreated) is shown above test. Data were not obtained on Aug. 5, 7, and in solid-line graph), (24).

Figure 6. Triangular^ trap being stapled to tree in experiment to determine effectiveness of mass trapping.

114

Figure 7.

PEST

MANAGEMENT WITH

INSECT

SEX

ATTRACTANTS

Drinking cup monitor trap showing high-potency phstic laminated dispenser of disparlure.

7.

BEROZA

Control of the Gypsy Moth

115

r e l a t i v e to mating on the untreated i s l a n d where 85.4% mated d e s p i t e a very low i n i t i a l p o p u l a t i o n . However, the trend o f the data, trap captures and post-season egg-mass counts, def i n i t e l y showed the e f f e c t of the d i s p a r l u r e confusant and o f the mass t r a p p i n g . For example, captures i n monitor t r a p s t o t a l l e d 14 i n the area t r e a t e d only w i t h i n s e c t i c i d e compared w i t h 5 each i n the other two t r e a t e d areas and 467 i n the unt r e a t e d c o n t r o l . (Because o f an unexplained n a t u r a l c o l l a p s e of gypsy moth populations throughout the Northeastern U.S. i n 1974, post-season egg-mass counts were low i n a l l p l o t s , i n c l u d i n g the c o n t r o l . ) I t i s considered encouraging that t h e only area i n which no post-season egg masses a t a l l were found was the one t r e a t e d w i t h i n s e c t i c i d e and then w i t h the d i s p a r l u r e microcapsules. I n the area t r e a t e d w i t h i n s e c t i c i d e only, 8 egg masses were recovered. A l s o , 1151 moths were taken i n the area that was t r e a t e d w i t h i n s e c t i c i d e and mass trapped, which shows that a s u b s t a n t i a l number o f males were l e f t i n the i n s e c t i c i d e - t r e a t e d area and were a v a i l a b l e f o r mating w i t h the untethered females. I n a d d i t i o n t o the p o t e n t i a l u s e f u l ness o f mass t r a p p i n g i n c o n t r o l l i n g low-density p o p u l a t i o n s , mapping o f the t r a p captures could a t the same time p r o v i d e an assessment o f the d i s t r i b u t i o n and s i z e of i n c i p i e n t i n f e s t a t i o n s i n s p o t t y but g e n e r a l l y i n f e s t e d areas. By u t i l i z i n g the high-potency Hereon b a i t dispensers i n the monitor t r a p s , we found t h a t males could be captured i n the d i s p a r l u r e - t r e a t e d areas. (Very few i n s e c t s were captured by the monitor traps b a i t e d w i t h 10-yg d i s p a r l u r e i n the 1973 t e s t s , an i n d i c a t i o n t h a t much more potent t r a p s would be needed t o monitor the l u r e - t r e a t e d areas.) Indeed, the numbers o f males taken i n the high-potency t r a p s g r e a t l y exceeded the numbers o f untethered females found mated. For example, only 1 and 2 untethered females were found mated i n the areas t r e a t e d w i t h 10 + 10 and 20 g l u r e / h e c t a r e when 32 and 22 males, r e s p e c t i v e l y , were captured by the high-potency monitor t r a p s i n the same areas. Thus, the high-potency t r a p s should be u s e f u l i n monitoring d i s p a r l u r e - t r e a t e d areas, i n d e s i g n a t i n g areas t h a t r e q u i r e a d d i t i o n a l treatment or a t t e n t i o n , i n s i g n a l l i n g a t an e a r l y stage (before mating occurs) that the d i s p a r l u r e c o n c e n t r a t i o n i n the a i r i s f a l l i n g below the l e v e l r e q u i r e d t o d i s r u p t o r i e n t a t i o n so another treatment can be made to m a i n t a i n d i s r u p t i o n , and i n p r o v i d i n g a measure o f the mating p o t e n t i a l and perhaps even of the r e s i d u a l male p o p u l a t i o n i n an area. O v e r a l l , the 1974 f i e l d r e s u l t s i n d i c a t e that a i r permeat i o n w i t h slow-release d i s p a r l u r e microcapsules a p p l i e d a t the r a t e o f 20 g l u r e / h e c t a r e i s e f f e c t i v e i n reducing mating success i n l o w - l e v e l i n f e s t a t i o n s o f the gypsy moth o r i n i n f e s t a t i o n s brought t o low l e v e l s w i t h an i n s e c t i c i d e .

116 Need f o r Monitoring

PEST

MANAGEMENT

WITH

INSECT SEX

ATTRACTANTS

Populations

I f we are to make optimum progress i n d i r e c t i n s e c t c o n t r o l w i t h such population-dependent t o o l s as pheromones, accurate means of e s t i m a t i n g i n s e c t populations have to be developed. With such estimates a proper judgment can be made as t o whether the pheromone approach i s a p p l i c a b l e i n a given s i t u a t i o n , and they can a l s o be v a l u a b l e i n assessing progress as i n s e c t populat i o n s are reduced t o very low l e v e l s . P r e s e n t l y , traps a r e the c h i e f t o o l f o r such assessments, and a high-potency trap w i t h a uniform and constant a t t r a c t i o n would be i n v a l u a b l e . Toward t h i s end, a b a i t dispenser that emits s u f f i c i e n t l u r e a t a cons t a n t r a t e (aside from the e f f e c t of temperature) i s needed. I n t h i s regard, i t i s recognized that captures by pheromoneb a i t e d traps may not be p r o p o r t i o n a l to i n s e c t populations when i n f e s t a t i o n s are of moderate to high d e n s i t y because n a t i v e f e males compete w i t h l u r e - b a i t e d t r a p s . Thus, a t l e a s t t h e o r e t i c a l l y , the traps should make fewer captures p r o p o r t i o n a l l y as competition from n a t i v e females i n c r e a s e s . We b e l i e v e t h i s e f f e c t was operating i n the 1973 gypsy moth t r i a l s (24). Other Studies Microencapsulated pheromones have a l s o been t e s t e d as confus ant s against the c o d l i n g moth (Laspeyresia pomonella ( L . ) ) and the o r i e n t a l f r u i t moth. I n areas t r e a t e d w i t h c o d l i n g moth pheromone, trap captures of the moth i n monitor traps were s u b s t a n t i a l l y suppressed (compared w i t h those i n an unt r e a t e d area) f o r up t o two weeks ( M o f f i t t e t a l . , unpublished). S i m i l a r r e s u l t s were obtained w i t h the o r i e n t a l f r u i t moth w i t h trap captures being suppressed f o r up t o 5 weeks (&). In a d d i t i o n , attempts were made to d i s r u p t mate-finding of the gypsy moth w i t h the o l e f i n precursor of d i s p a r l u r e , which has been shown to be an e f f e c t i v e i n h i b i t o r of the response of males to d i s p a r l u r e i n traps (26). A p p l i c a t i o n s up to 61.75 g of the o l e f i n / h e c t a r e i n microcapsules were found i n e f f e c t i v e i n t r i a l s conducted before and during the moth f l i g h t season. In concurrent t e s t s w i t h 15 g d i s p a r l u r e / h e c t a r e f e r t i l i z a t i o n of females was s i g n i f i c a n t l y reduced (27). A s i m i l a r attempt to d i s r u p t mate-finding w i t h an i n h i b i t o r of the c o d l i n g moth pheromone (28) was l i k e w i s e unrewarding ( M o f f i t t et a l . , unpublished) . Summarizing Comments Sex a t t r a c t a n t pheromones provide a promising means of cont r o l l i n g i n s e c t pests. T h e i r use i n the d e t e c t i o n of pest b u i l d u p s , p a r t i c u l a r l y f o r the guidance of c o n t r o l measures, appears to be e s t a b l i s h e d . However, f o r the use of pheromones i n d i r e c t c o n t r o l of i n s e c t s , as i n mass trapping or a i r -

7.

BEROZA

Control of the Gypsy Moth

117

permeation, considerable technology needs to be developed, e s p e c i a l l y s i n c e much o f t h i s technology i s l i k e l y t o d i f f e r w i t h d i f f e r e n t s p e c i e s . E f f o r t s thus f a r have shown promise against s e v e r a l important i n s e c t pests. Acknowledgment. The author thanks the many i n v e s t i g a t o r s , both i n and out of the USDA, whose c o n t r i b u t i o n s form the b a s i s of t h i s paper.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Beroza, M. J. Chromatogr. Sci. (1975) 13, 314-21. USDA-APHIS. Private communication. Holbrook, R. F., Beroza, Μ., and Burgess, E. D. J. Econ. Entomol. (1960) 53, 751-6. Beroza, Μ., Gentry, C. R., Muschik, G. Μ., and Blythe, J. L. J. Econ. Entomol. (1973) 66, 1307-11. Gentry, C. R., Beroza, Μ., and Blythe, J. L. Environ. Entomol. (1975) 4, 227-8. Beroza, Μ., Muschik, G. Μ., Gentry, C. R. Nature (1973) 244, 149-150. Gentry, C. R., Beroza, Μ., and Payne, J. R. Proc. Ann. Con­ vention Southeastern Pecan Growers Assoc. (1975) 68, 107-13. Gentry, C. R., Beroza, Μ., Blythe, J. L., and Bierl, B. A. Environ. Entomol.(1975) 4, 822-824. Beroza, Μ., Bierl, Β. Α., Tardif, J . G. R., Cook, D. Α., and Paszek, Ε. C. J . Econ. Entomol. (1971) 64, 14991508. Fitzgerald, T. D., St. Clair, A. D., Daterman, G. Ε., and Smith, R. G. Environ. Entomol. (1973) 2, 607-10. Hardee, D. D., Graves, T. M . , McKibben, G. Η., Johnson, W. L., Gueldner, R. C., and Olsen, C. M. J. Econ. Entomol. (1974) 67, 44-6. McKibben, G. Η., Gueldner, R. C., Hedin, P. Α., Hardee, D. D., and Davich, T. B. J . Econ. Entomol. (1972) 65, 1512-4. McKibben, G. Η., Hardee, D. D., Davich, Τ. Β., Gueldner, R. C., and Hedin, P. A. J . Econ. Entomol. (1971) 64, 317-9. Beroza, Μ., Paszek, E. C., Mitchell, E. R., Bierl, Β. Α., McLaughlin, J . R., and Chambers, D. L. Environ. Entomol. (1974) 3, 926-8. Beroza, Μ., and Knipling, E. F. Science (1972) 177, 19-27. Knipling, E. F . , and McGuire, J. R., Jr. U. S. Dept. Agric. Inf. Bull. 308 (1966), 20 pp. Trammel, Κ., Roelofs, W. L., and Glass, Ε. H. J . Econ. Entomol. (1974) 67, 159-64. Beroza, Μ., Stevens, L. J., Bierl, Β. Α., Philips, F. M. and Tardif, J . G. R. Environ. Entomol. (1973) 2, 1051-7.

118

PEST MANAGEMENT WITH INSECT SEX ATTRACTANTS

19. Beroza, M. Agr. Chem. (1960) 15(7), 37-40. 20. Beroza, Μ., Inscoe, Μ. Ν., Schwartz, P. Η., Jr., Keplinger, M. L., and Mastri, C. W., Toxicol. Appl. Pharmacol. (1975) 31, 421-9. 21. Stevens, L. J., and Beroza, Μ., J. Econ. Entomol. (1972) 65, 1090-5. 22. Beroza, Μ., Bierl, Β. Α., James, P., and DeVilbiss, E. D. J. Econ. Entomol. (1975) 68, 369-72. 23. Bierl, Β. Α., Beroza, Μ., Collier, C. W. Science (1970) 170, 87-9. 24. Beroza, M., Hood, C. S., Trefrey, D., Leonard,D.Ε., Knipling, E. F., Klassen, W., and Stevens, L. J. J. Econ. Entomol. (1974) 67, 659-64. 25. Beroza, M., Hood, C. S., Trefrey, D., Leonard, D. Ε., Knipling, E. F., and Klassen, W. Environ. Entomol. (1975) 4, 705-711. 26. Cardé, R. T., Roelofs, W. L., and Doane, C. C. Nature (1973) 241, 474-5. 27. Cameron, Ε. Α., Schwalbe, C. P., Stevens, L. J., and Beroza, M. J. Econ. Entomol. (1975) 68, 158-60. 28. Hathaway, D. D., McGovern, T. P., Beroza, M., Moffitt, H. R., McDonough, L. Μ., and Butt, B. A. Environ. Entomol. (1974) 3, 522-4.