Management of Pesticide Resistance in Arthropod Pests - ACS

Chapter 10

Management of Pesticide Resistance in Arthropod Pests Research and Policy Issues B. A. Croft Department of Entomology, Oregon State University, Corvallis, OR 97331

Pesticide resistance management requires both technical progress in research and enlightened policies governing pesticide development, regulation, marketing and use. Improved monitoring systems, tactics of resistance management, models of resistance evolution, and experimentation on factors influencing resistance evolution have added to our ability to limit resistance in field populations of target pest insects. Greater emphasis on research in population genetics and ecology is needed to further extend this technology. Examples of successful resistance management with houseflies in Denmark, cotton bollworms in Australia, pear psylla in North America and a complex of pests and natural enemies on tree fruits in the United States demonstrate that policy-related factors can be a key to successful resistance management. Conversely, the lack of success in other pest systems may be due to antiquated policies. A recent case of resistance management in the spider mite Tetranychus urticae illustrates new policies by industry regarding research and pesticide labelling which will improve possibilities for resistance management and will extend the life of newly registered acaricides. Pesticide resistance management is a strategy of resistance containment or suppression using a variety of tactics, including pesticides and other nonchemical control measures (e.g. biological control). Beyond research, resistance management requires enlightened policies governing pesticide development, registration, marketing, regulation, and education. In this paper, progress in resistance management for arthropod pests is discussed, focusing on research, successful case histories of resistance management, policy limitations to resistance management, and future needs. 0097-6156/90AM21-O149$06.00A) © 1990 American Chemical Society

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MANAGING RESISTANCE TO AGROCHEMICALS P r o g r e s s i n R e s i s t a n c e Management R e s e a r c h R e s e a r c h on the e v o l u t i o n o f r e s i s t a n c e t o p e s t i c i d e s among a r t h r o p o d p e s t s began soon a f t e r t h i s phenomenon was w i d e l y d i s c o v e r e d i n the l a t e 1940's and 1950's (1-2; see a l s o G e o r g h i o u , t h i s volume). I n i t i a l l y , r e s e a r c h f o c u s e d on the g e n e t i c s , b i o c h e m i s t r y , and t o x i c o l o g y ( a l o n g w i t h l i m i t e d m o n i t o r i n g r e s e a r c h ) o f r e s i s t a n c e , as s c i e n t i s t s t r i e d t o b e t t e r document the b a s i c mechanisms i n v o l v e d ( 3 ) . The hope was t o c i r c u m v e n t or d i m i n i s h the impact o f r e s i s t a n c e , b u t b e c a u s e t h e s e i n i t i a l i n v e s t i g a t i o n s l e d t o so l i t t l e p r a c t i c a l s u c c e s s , an " i n e v i t a b i l i t y syndrome" s e t i n . G i v e n enough time and i n t e n s i t y o f p e s t i c i d e use, i t was thought t h a t c e r t a i n t r o u b l e s o m e s p e c i e s would e v e n t u a l l y d e v e l o p r e s i s t a n c e and t h e r e was l i t t l e one c o u l d do about i t . R e s i s t a n c e was o f t e n c o n s i d e r e d i r r e v e r s i b l e . Once l o s t , a compound c o u l d not be u s e d a g a i n and s u b s t i t u t e m a t e r i a l s had to be found as soon as p o s s i b l e . Resistance research other t h a n t h a t d i r e c t e d a t documenting r e s i s t a n c e e p i s o d e s became somewhat u n f a s h i o n a b l e and neglected. T r e a t i n g p e s t i c i d e s as s h o r t - t e r m t o o l s f o r s u p p r e s s i o n o f p e s t s c a u s e d no s e r i o u s problems as l o n g as new m a t e r i a l s were readily available. I n f a c t , the o b s o l e s c e n c e o f many compounds would have o c c u r r e d anyway because o f the r a p i d p r o g r e s s b e i n g made i n the development o f s a f e r , more e f f e c t i v e p e s t i c i d e s . However, i n the e a r l y 1970's, as economic and r e g u l a t o r y c o n s t r a i n t s on development o f new p e s t i c i d e s i n c r e a s e d , the number o f new c h e m i c a l s b e i n g i n t r o d u c e d a n n u a l l y , d e c l i n e d worldwide ( 4 ) . C o u p l e d w i t h a r a p i d i n c r e a s e i n the number o f r e s i s t a n c e c a s e s , the d e c l i n e i n the a v a i l a b i l i t y o f p e s t i c i d e s o n l y i n t e n s i f i e d the need f o r new approaches to p e s t c o n t r o l and r e s i s t a n c e problems. An i m p o r t a n t major r e s p o n s e t o r e s i s t a n c e problems was the emergence and s p r e a d o f i n t e g r a t e d p e s t management (IPM) (5). A l t h o u g h the r o o t s o f IPM t r a c e back t o the 1930's, w i d e s p r e a d a d o p t i o n d i d not b e g i n u n t i l the 1970's. IPM emphasized a more t h o r o u g h s t u d y o f the e c o l o g y o f p e s t s , the g r e a t e r use o f b i o l o g i c a l c o n t r o l agents, a wider array of other nonchemical t a c t i c s o f p e s t c o n t r o l , and b e t t e r p e s t i c i d e management. IPM a l s o r e k i n d l e d i n t e r e s t i n f i n d i n g a l t e r n a t i v e ways to d e l a y o r a v o i d resistance i n pests. U s i n g m o d e l i n g t e c h n i q u e s (e.g., 6-11). s c i e n t i s t s i d e n t i f i e d a d i v e r s i t y o f f a c t o r s i n f l u e n c i n g r e s i s t a n c e i n the l a t e 1970'se a r l y 1980's. W i t h t h i s more complete and i n t e g r a t e d t h e o r e t i c a l framework, more e x t e n s i v e r e s e a r c h on r e s i s t a n c e development i n the l a b o r a t o r y and f i e l d was p u r s u e d . E v e n t u a l l y , a more complete range o f p h y s i o l o g i c a l , g e n e t i c , e c o l o g i c a l and o p e r a t i o n a l ( i . e . , those under c o n t r o l o f the manager) f a c t o r s i n f l u e n c i n g r e s i s t a n c e were i d e n t i f i e d (6-7) and i n v e s t i g a t e d ( 1 2 ) . By the 1980's, a p p l i e d r e s e a r c h on new t a c t i c s , m o n i t o r i n g methods, and i n t e g r a t e d systems o f r e s i s t a n c e management began t o be more w i d e l y d e v e l o p e d (13-14). I n a d d i t i o n , some o f the i n s t i t u t i o n a l , i n d u s t r y - r e l a t e d , and r e g u l a t o r y c o n s t r a i n t s which p r e v i o u s l y had l i m i t e d r e s i s t a n c e management programs were b e g i n n i n g to be a r t i c u l a t e d (e.g., 14). W i t h t h e s e advances,

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s c i e n t i s t s began to c o n s i d e r r e s i s t a n c e as a more manageable phenomenon. The r e n a i s s a n c e i n r e s i s t a n c e and r e s i s t a n c e management r e s e a r c h i n the U n i t e d S t a t e s was summarized i n a N a t i o n a l Academy of Science/National Research C o u n c i l study e n t i t l e d P e s t i c i d e Resistance: S t r a t e g i e s and T a c t i c s f o r Management (12). In t h i s forum, s c i e n t i s t s met t o d i s c u s s the s t a t u s o f r e s i s t a n c e r e s e a r c h i n a broad context. Those p r e s e n t r e p r e s e n t e d a b r o a d range o f d i s c i p l i n e s from a g r i c u l t u r e and human h e a l t h . T h i s paper f o c u s e s on p r o g r e s s made i n r e s e a r c h and i m p l e m e n t a t i o n o f r e s i s t a n c e management s i n c e the NAS r e p o r t . It g e n e r a l i z e s from the r e p o r t s g i v e n e a r l i e r i n t h i s symposium. W h i l e r e s i s t a n c e management o f a r t h r o p o d s p e c i e s i s s p e c i f i c a l l y a d d r e s s e d , t h e s e p r i n c i p l e s may be a p p l i c a b l e t o o t h e r p e s t s as well. R e s e a r c h on Management o f P e s t i c i d e

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Important t e c h n i c a l i s s u e s l i m i t i n g the development o f r e s i s t a n c e management systems can be s u b d i v i d e d i n t o b a s i c and a p p l i e d categories. While one may r e c o g n i z e c o n s i d e r a b l e o v e r l a p i n t h e s e c a t e g o r i e s , the d i s t i n c t i o n i s s t i l l u s e f u l . A l s o , r e s e a r c h emphasis can be o r g a n i z e d by l e v e l o f r e s o l u t i o n r a n g i n g from m o l e c u l a r and c e l l u l a r b i o l o g y to p o p u l a t i o n and community e c o l o g y (Figure 1). As n o t e d e a r l i e r , e a r l y r e s e a r c h e f f o r t s were c o n d u c t e d m o s t l y a t the s u b o r g a n i s m a l and o r g a n i s m a l l e v e l s . However, e f f o r t s i d e a l l y must i n c l u d e the f u l l spectrum o f d i s c i p l i n e s shown i n F i g u r e 1. As d i s c u s s e d below, t h e r e a r e some major gaps i n the r e s e a r c h e f f o r t p r e s e n t l y underway i n r e s i s t a n c e management. Basic Science Aspects. The u n d e r l y i n g mechanisms o f r e s i s t a n c e a t the c e l l u l a r or o r g a n i s m a l l e v e l , i n c l u d i n g the g e n e t i c s , b i o c h e m i s t r y , and t o x i c o l o g y o f r e s i s t a n c e , c o n t i n u e s to be o f extreme i n t e r e s t to s c i e n t i s t s s t u d y i n g p e s t i c i d e r e s i s t a n c e (1213; see B r a t t s t e n , i n t h i s volume). T h i s type o f r e s e a r c h i s fundamental to r e a c h an u n d e r s t a n d i n g o f r e s i s t a n c e , i n c l u d i n g means to overcome i t . For example, knowing the g e n e t i c b a s i s o f r e s i s t a n c e i s a c r i t i c a l to u n d e r s t a n d i n g the p o p u l a t i o n g e n e t i c s o f p e s t i c i d e r e s i s t a n c e (Denholm e t a l . , t h i s v o l u m e ) . Basic a s p e c t s o f r e s i s t a n c e are a l s o i m p o r t a n t i n the d e s i g n o f new p e s t i c i d e s w i t h n o v e l modes o f a c t i o n t h a t do not show c r o s s r e s i s t a n c e to e a r l i e r p e s t i c i d e s (15; B r a t t s t e n , t h i s volume); i n c h o o s i n g a p p r o p r i a t e s y n e r g i s t s to overcome r e s i s t a n c e mechanisms (16); i n i d e n t i f y i n g p e s t i c i d e s t h a t s e l e c t l e s s i n t e n s i v e l y (12,17); and i n d e v e l o p i n g m o n i t o r i n g t e c h n i q u e s f o r p e s t i c i d e r e s i s t a n c e (18). More r e c e n t l y , b a s i c r e s e a r c h has i n c l u d e d use o f m o l e c u l a r t e c h n i q u e s to i d e n t i f y r e s i s t a n c e genes and gene p r o d u c t s (enzymes and r e c e p t o r s ) (e.g., 19-20: Brown, t h i s v o l u m e ) . This information adds to our u n d e r s t a n d i n g o f p e s t i c i d e t a r g e t s i t e s , p e s t i c i d e pharmacodynamics and g e n e t i c mechanisms, such as changes i n s t r u c t u r a l genes, a m p l i f i c a t i o n o f s t r u c t u r a l genes and a l t e r a t i o n i n r a t e s o f gene r e g u l a t i o n (12).

F i g u r e 1.

D i s c i p l i n e needs i n p e s t i c i d e r e s i s t a n c e

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A n o t h e r l e v e l o f f a c t o r s i n f l u e n c i n g r e s i s t a n c e development i s the l i f e h i s t o r y l e v e l . For example, i t has l o n g been known t h a t organisms w i t h r a p i d r e p r o d u c t i v e r a t e s d e v e l o p r e s i s t a n c e more r a p i d l y and more f r e q u e n t l y t h a n do p e s t s w i t h l o w e r r e p r o d u c t i v e r a t e s (6.21-22). Other l i f e h i s t o r y f a c t o r s i n f l u e n c i n g r e s i s t a n c e development i n c l u d e f e c u n d i t y , r e p r o d u c t i o n , f e e d i n g h a b i t s (e.g., monophagy/polyphagy), o c c u r r e n c e i n r e f u g i a , and m i g r a t i o n c h a r a c t e r i s t i c s . For example, the r e l a t i o n s h i p between the number o f g e n e r a t i o n s p e r season and the r a t e o f r e s i s t a n c e development has been documented f o r many a g r i c u l t u r a l p e s t s exposed t o p e s t i c i d e s o v e r l o n g time p e r i o d s i n a p a r t i c u l a r h a b i t a t ( e . g . , 11,21). More r e c e n t l y , s t u d i e s o f how the l i f e h i s t o r y a t t r i b u t e s o f a s p e c i e s i n f l u e n c e r e s i s t a n c e development have been i n v e s t i g a t e d u s i n g models, and by comparing t h e i r o u t p u t w i t h r e s i s t a n c e patterns observed i n f i e l d populations. Denholm e t a l . ( i n t h i s v o l u m e ) , i l l u s t r a t e t h i s type o f r e s e a r c h f o r the common h o u s e f l y , Musca domestica. I n a complex o f s p e c i e s a s s o c i a t e d w i t h a p p l e o r c h a r d s ( i n c l u d i n g b o t h p e s t s and n a t u r a l enemies), T a b a s h n i k and C r o f t (11,23) r e p o r t e d t h a t v a r i a t i o n s i n a t t r i b u t e s among s p e c i e s o f l i f e h i s t o r y d i f f e r e n t i a l l y a f f e c t r e s i s t a n c e development. F u r t h e r m o r e , the i n f l u e n c e o f these f a c t o r s o f t e n depends on e c o l o g i c a l c o n d i t i o n s p r e s e n t i n the environment s u r r o u n d i n g the t r e a t e d h a b i t a t . For example, the l e v e l o f r e s i s t a n c e d i l u t i o n by i m m i g r a t i n g s u s c e p t i b l e i n d i v i d u a l s g r e a t l y i n f l u e n c e s the e f f e c t o f some o p e r a t i o n a l f a c t o r s such as dose and f r e q u e n c y o f s p r a y i n g on r e s i s t a n c e development. I n g e n e r a l , t h e y r e p o r t e d t h a t r e s i s t a n c e i s l e a s t common i n s p e c i e s t h a t have low r e s i d e n c y l e v e l s of r e s i s t a n t i n d i v i d u a l s i n r e l a t i o n to high l e v e l s of i m m i g r a t i o n o f s u s c e p t i b l e i n d i v i d u a l s i n t o the t r e a t e d environment. Furthermore, they c o n c l u d e d t h a t under most e c o l o g i c a l c o n d i t i o n s , a low dose and low a p p l i c a t i o n f r e q u e n c y approach i s the most p r e f e r a b l e s t r a t e g y o f r e s i s t a n c e management. These s t u d i e s o f the i n d i v i d u a l and i n t e g r a t e d e f f e c t s o f l i f e h i s t o r y have i d e n t i f i e d s e n s i t i v e f a c t o r s w h i c h g o v e r n r a t e s o f r e s i s t a n c e development. G e n e r a l l y , r e s i s t a n c e p a t t e r n s can b e s t be e x p l a i n e d a t the p o p u l a t i o n l e v e l by i n t e g r a t i n g the i n f o r m a t i o n o b t a i n e d from the s u b o r g a n i s m a l and o r g a n i s m a l l e v e l s d i s c u s s e d above ( e . g . , g e n e t i c s , l i f e h i s t o r y , e t c ) . When t h i s i n f o r m a t i o n i s s y n t h e s i z e d i n t o a model o f p o p u l a t i o n dynamics, the i n f l u e n c e o f any s i n g l e f a c t o r can be more c o m p l e t e l y e v a l u a t e d f o r i t s i n f l u e n c e on r e s i s t a n c e development (see n e x t s e c t i o n ) . Another l e v e l of f a c t o r s i n f l u e n c i n g r e s i s t a n c e which r e q u i r e s much g r e a t e r e f f o r t i n b a s i c r e s e a r c h i s the e c o l o g i c a l o r population genetics l e v e l . As compared t o the two a r e a s d i s c u s s e d e a r l i e r , t h i s l e v e l has r e c e i v e d much l e s s emphasis (3,24; see Denholm e t a l . i n t h i s volume). Most models o f p o p u l a t i o n g e n e t i c s f o r p e s t i c i d e r e s i s t a n c e are t h e o r e t i c a l , w i t h l i m i t e d v a l i d a t i o n . These models o f t e n are b a s e d on s i m p l e g e n e t i c assumptions d e s c r i b i n g a v e r y g e n e r a l i z e d p e s t (25-28), and u s u a l l y f o c u s on p o p u l a t i o n s o f a s i n g l e s p e c i e s . V e r y few have e x p l o r e d r e s i s t a n c e development i n s p e c i e s complexes o f p e s t s and b e n e f i c i a l a r t h r o p o d s o r communities o f s p e c i e s (e.g., 11,23).

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A n o t h e r l i m i t a t i o n t o p r o g r e s s made i n p o p u l a t i o n g e n e t i c s o f p e s t i c i d e r e s i s t a n c e i s the assumption t h a t r e s i s t a n c e i s a l m o s t always due t o s i n g l e - g e n e phenomena (27,29). W h i l e t h i s l e v e l o f i n v e s t i g a t i o n may be adequate f o r many c a s e s o f r e s i s t a n c e (e.g. f o r the h o u s e f l y ; 30), the i n c i d e n c e o f p o l y g e n i c r e s i s t a n c e i s becoming i n c r e a s i n g l y w e l l documented. V e r y l i k e l y , s t u d y o f p o l y g e n i c r e s i s t a n c e w i l l become more i m p o r t a n t as our u n d e r s t a n d i n g o f the p o p u l a t i o n g e n e t i c s o f f i e l d p o p u l a t i o n s improves. More complex g e n e t i c systems o f r e s i s t a n c e must be v i g o r o u s l y i n v e s t i g a t e d p a r t i c u l a r l y f o r f a c t o r s such as the f i t n e s s e s a s s o c i a t e d w i t h r e s i s t a n c e b o t h i n the p r e s e n c e and absence o f i n s e c t i c i d e s , and l i n k a g e o f r e s i s t a n c e genes t o o t h e r r e s i s t a n c e genes (3.24.27-28). I n the p o p u l a t i o n dynamics a r e a , new methods f o r m o n i t o r i n g movement o f h i g h l y m o b i l e s p e c i e s are b e g i n n i n g t o be d e v e l o p e d (31), b u t l i t t l e r e s e a r c h t o l i n k m i g r a t i o n phenomena t o r a t e s o f gene f l o w i n r e s i s t a n t s p e c i e s has been r e p o r t e d . R e s e a r c h remains a t the e l e m e n t a r y l e v e l o f t r y i n g t o d e v e l o p a p p r o p r i a t e markers ( e i t h e r g e n e t i c o r m o r p h o l o g i c a l ) and s a m p l i n g methods t h a t w i l l i n d i c a t e changes i n the f r e q u e n c y o f r e s i s t a n c e genes i n p o p u l a t i o n s as s e l e c t i o n (both f o r r e s i s t a n c e i n the p r e s e n c e o f p e s t i c i d e s and a g a i n s t r e s i s t a n c e i n t h e i r a b s e n c e ) , i m m i g r a t i o n and o t h e r p o p u l a t i o n p r o c e s s e s o c c u r o v e r time. C o n t r i b u t i n g t o the l a c k o f s t u d y o f the g e n e t i c s o f p e s t i c i d e r e s i s t a n c e a t the p o p u l a t i o n l e v e l i s t h a t many a p p l i e d s c i e n t i s t s a r e i n a d e q u a t e l y t r a i n e d t o work i n t h i s a r e a . F u r t h e r m o r e , i t has been v e r y d i f f i c u l t t o c o n v i n c e b a s i c s c i e n t i s t s w i t h p o p u l a t i o n g e n e t i c s e x p e r t i s e t o use r e s i s t a n c e as a model f o r s t u d y i n g evolutionary processes. Even when such s c i e n t i s t s a r e a t t r a c t e d to r e s i s t a n c e r e s e a r c h , they a r e o f t e n s u r p r i s e d and d i s c o u r a g e d by the r e l a t i v e d i f f i c u l t y o f o b t a i n i n g funds f o r r e s i s t a n c e r e s e a r c h as compared to some more b a s i c a s p e c t s o f e v o l u t i o n a r y b i o l o g y . There i s some e v i d e n c e t h a t t h i s gap i s b e i n g b r i d g e d , i n p a r t , by the i n v o l v e m e n t o f b a s i c r e s e a r c h e r s i n symposia ( e . g . , 25.27-28; a l s o Dehholm e t a l . , t h i s volume) and by the i n c r e a s i n g use o f examples o f r e s i s t a n c e management i n t e a c h i n g e v o l u t i o n a r y b i o l o g y , g e n e t i c s , and a p p l i e d s c i e n c e s as w e l l . I n t e r a c t i o n s between b a s i c and a p p l i e d s c i e n t i s t may o c c u r more f r e q u e n t l y as we v i e w a r t h r o p o d r e s i s t a n c e as an example o f b i o c i d e r e s i s t a n c e as m a n i f e s t e d i n such d i v e r s e a r e a s as a n t i b i o t i c r e s i s t a n c e i n human and p l a n t pathogens, heavy m e t a l r e s i s t a n c e i n p l a n t s . A p p l i e d Science Aspects. P r o g r e s s has been made i n a p p l y i n g b a s i c r e s e a r c h i n the f i e l d l a r g e l y because o f the need t o s o l v e the r e s i s t a n c e p r o b l e m (12-14). D e t e c t i o n methods, m o n i t o r i n g programs, new t a c t i c s , and i n t e g r a t i o n o f t h e s e elements i n t o r e s i s t a n c e management programs a r e b e g i n n i n g t o be u s e d i n s e v e r a l major c r o p p i n g systems (e.g., G e l e r n t e r , Dennehy and Nyrop, B u l l and Menn, R i l e y i n t h i s volume). D e t e c t i o n and m o n i t o r i n g o f r e s i s t a n c e i s p r o d u c i n g p r o m i s i n g r e s u l t s u s i n g c l a s s i c a l b i o a s s a y , b i o c h e m i c a l enzyme t e s t s , i m m u n o l o g i c a l t e c h n i q u e s (e.g., ELISA) and b i o t e c h n o l o g i c a l p r o b e s w i t h a p p r o p r i a t e DNA o r RNA segments (12,18; Dennehy and Nyrop, B u l l and Menn and R i l e y , t h i s volume). In a d d i t i o n , s t a t i s t i c a l

10. CROFT


155

methods u s e d f o r d e t e c t i n g p e s t i c i d e r e s i s t a n c e a r e b e i n g b e t t e r addressed (32). These t o o l s w i l l be u s e f u l i n c a l c u l a t i n g t h e c o s t s f o r r e s i s t a n c e m o n i t o r i n g and t h e f e a s i b i l i t y o f r e s i s t a n c e detection. L a r g e d a t a b a s e s c o n t a i n i n g base l i n e s u s c e p t i b i l i t y i n f o r m a t i o n f o r p e s t s when f i r s t exposed t o p e s t i c i d e s and s i m i l a r r e s i s t a n c e s u r v e y d a t a a r e b e i n g m a i n t a i n e d b y WHO, FAO, EPPO and o t h e r s ( 1 2 ) . As t h e s e d a t a b a s e s become more w i d e l y a v a i l a b l e t h r o u g h computer t e l e c o m m u n i c a t i o n l i n k s , b e t t e r d e c i s i o n s about r e s i s t a n c e management s h o u l d be p o s s i b l e . A v a r i e t y o f new t a c t i c s t o manage r e s i s t a n c e t o p e s t i c i d e s have been p r o p o s e d i n r e c e n t y e a r s , w i t h most f o c u s i n g on new p e s t i c i d e s and t h e i r a p p l i c a t i o n ( 1 2 ) . S u g g e s t i o n s u s e s o f r o t a t i o n s , a l t e r n a t i o n s and m i x t u r e s o f p e s t i c i d e s a r e coming from m o d e l i n g s t u d i e s o f r e s i s t a n c e development ( e . g . , 6-8.11). b u t , o n l y l i m i t e d e x p e r i m e n t a l s t u d i e s e v a l u a t i n g t h e s e methods have been r e p o r t e d . R e c e n t l y , a t t e n t i o n has f o c u s e d on use o f g e n e t i c a l l y improved p e s t i c i d e s and c r o p s , such t h o s e b a s e d on as m o d i f i e d s t r a i n s o f Bacillus thuringiensis o r c r o p s c o n t a i n i n g the e n d o t o x i n o f t h i s i n s e c t pathogen ( e . g . , G e l e r n t e r , t h i s v o l u m e ) . Thus f a r , many o f t h e s e measures have n o t been t e s t e d i n t h e f i e l d . P r o b l e m a t i c i n t e s t i n g r e s i s t a n c e management t a c t i c s i s t h e d i f f i c u l t y o f m a i n t a i n i n g e x p e r i m e n t a l a r e a s t o measure impacts on r e g i o n a l p o p u l a t i o n s o f p e s t s and t h e i m p r a c t i c a l i t y o f m a i n t a i n i n g u n t r e a t e d check p l o t s f o r comparison ( 1 2 ) . I n t e g r a t i o n o f t a c t i c s as p a r t o f an o v e r a l l s t r a t e g y o f r e s i s t a n c e management i n v o l v e s m o n i t o r i n g and m o d e l i n g as w e l l as a p l a n o f i m p l e m e n t a t i o n ( F i g u r e 2 ) . E n v i r o n m e n t a l m o n i t o r i n g and r e g u l a r e v a l u a t i o n o f c h a n g i n g t r e n d s i n economic f a c t o r s and p o l i c y must be c o n s i d e r e d . As i l l u s t r a t e d a t t h i s c o n f e r e n c e , p r o t o t y p e r e s i s t a n c e management systems f o r s p e c i e s such as s p i d e r m i t e s on a p p l e (Dennehy and Nyrop, t h i s v o l . ; see d i s c u s s i o n l a t e r i n t h i s p a p e r ) and Heliothis spp. on c o t t o n ( B u l l and Menn, R i l e y , t h i s v o l . ) a r e b e g i n n i n g t o be d e p l o y e d i n t h e f i e l d . These programs i l l u s t r a t e t h a t such systems v a r y g r e a t l y i n t h e i r t e m p o r a l and s p a t i a l s c a l e s o f a p p l i c a t i o n . I n t h e case o f s p i d e r m i t e s , r e s i s t a n c e c a n be managed i n s m a l l b l o c k s o f t r e e s , whereas w i t h Heliothis spp. whole r e g i o n s must be c o n s i d e r e d b e c a u s e o f t h e h i g h l y d i s p e r s i v e nature o f the i n s e c t . A t p r e s e n t , o u r u n d e r s t a n d i n g o f how a p e s t i c i d e r e s i s t a n c e management system s h o u l d be o r g a n i z e d i s r u d i m e n t a r y ( F i g u r e 2 ) . However, many o f t h e p r i n c i p l e s u s e d i n t h e d e s i g n o f IPM systems a r e a l s o a p p r o p r i a t e t o p e s t i c i d e r e s i s t a n c e management d e s i g n . As i n IPM systems, r e s i s t a n c e m o n i t o r i n g , m o d e l i n g and p r e d i c t i o n , and i m p l e m e n t a t i o n must be d e v e l o p e d and l i n k e d i n a t i m e l y manner ( F i g u r e 2 ) . S p a t i a l s c a l e s f o r m o n i t o r i n g and managing a p e s t o r p e s t complex must be o p t i m a l l y d e t e r m i n e d and i n f o r m a t i o n o f t e n must be t r a n s m i t t e d r a p i d l y f o r t h e program t o o p e r a t e e f f e c t i v e l y . As has been p o i n t e d o u t by many a u t h o r s (33-34: B u l l and Menn, R i l e y , t h i s volume), r e s i s t a n c e management s h o u l d be c o n s i d e r e d a s u b s e t o f IPM and s h o u l d o p e r a t e w i t h i n t h e c o n f i n e s o f such a system. As IPM improves, so s h o u l d r e s i s t a n c e management and v i c e versa.

156

MANAGING RESISTANCE

Environmental Monitoring

TO AGROCHEMICALS

Economic/Policy Environment

Pesticide Resistance Management Modei(s)

Delivery System IPM, PRM, Manager

Multi-species Pest/Natural Enemy Complex

Resistance Detection/Survey

Cropping System F i g u r e 2. system.

Components o f a p e s t i c i d e r e s i s t a n c e

management (PRM)

10. CROFT


157

Case H i s t o r i e s o f R e s i s t a n c e Management I m p l e m e n t a t i o n S e v e r a l c a s e s h i s t o r i e s i n which r e s i s t a n c e management h a s been s u c c e s s f u l l y a p p l i e d are reviewed i n t h i s s e c t i o n along with other l e s s s u c c e s s f u l examples ( T a b l e I ) . These c a s e h i s t o r i e s h i g h l i g h t some o f t h e r e s e a r c h needs and p o l i c y l i m i t a t i o n s o f r e s i s t a n c e management. I n some i n s t a n c e s , t h e same p e s t s p e c i e s o r a c l o s e l y r e l a t e d s p e c i e s a r e t h e s u b j e c t o f s u c c e s s f u l r e s i s t a n c e management as w e l l as f a i l u r e . T h i s i l l u s t r a t e s t h a t s u c c e s s c a n be s i t e s p e c i f i c , v a r y i n g from a r e a t o a r e a due t o t h e " r e s i s t a n c e environment" ( i . e . , organim b i o l o g y , e c o l o g y and i n s i t u t i o n a l policy). I n making g e n e r a l comparisons, k e y f a c t o r s a r e i d e n t i f i e d t h a t may have d e t e r m i n e d t h e s u c c e s s o f a g i v e n r e s i s t a n c e management attempt. As might be e x p e c t e d , no s i n g l e f a c t o r i s always r e s p o n s i b l e , b u t some t r e n d s a r e a p p a r e n t . D e t e r m i n i n g why r e s i s t a n c e management does o r does n o t work i s a c h a l l e n g e , given the many f a c t o r s i n v o l v e d . Also, i t i s probably inappropriate to c h a r a c t e r i z e c e r t a i n c a s e h i s t o r i e s as f a i l u r e s , j u s t b e c a u s e p r o g r e s s h a s been slow. I n f a c t , we a r e l e a r n i n g much about what does and does n o t work from t h e s e examples. S u c c e s s f u l R e s i s t a n c e Management. I n A u s t r a l i a , r e s i s t a n c e t o p y r e t h r o i d (SP) i n s e c t i c i d e s was c o n f i r m e d i n l a b o r a t o r y t e s t s o f the c o t t o n b o l l w o r m Heliothis armigera after f i e l d control failures i n c o t t o n and soybean o c c u r r e d i n t h e E m e r a l d I r r i g a t i o n D i s t r i c t o f Q u e e n s l a n d i n 1983. W i t h i n a few months, a s t r a t e g y t o manage the r e s i s t a n c e p r o b l e m was p r o p o s e d b y s t a t e a u t h o r i t i e s a f t e r c o n s u l t a t i o n w i t h f e d e r a l CSIRO r e s e a r c h a u t h o r i t i e s , p e s t i c i d e companies, and growers. The program i n v o l v e d r e s t r i c t i n g SP u s e on a l l c r o p s i n t h e a r e a t o a 42-day p e r i o d d u r i n g t h e m i d d l e o f t h e growing s e a s o n ( 3 5 ) . Adherence t o t h e program i s v o l u n t a r y i n New South Wales, b u t i s p o t e n t i a l l y e n f o r c e a b l e i n Queensland. Even though t h e s e r e s t r i c t i o n s i n p e s t i c i d e u s e a r e a f i n a n c i a l b u r d e n i n some c a s e s , t h e r e h a s been no e f f o r t t o e n f o r c e u s e o f t h e program i n e i t h e r s t a t e , and c o m p l i a n c e appears t o be a l m o s t compete (Daly, J . C , p e r s . comm., 1988). The program h a s been j u d g e d a s u c c e s s inasmuch as t h e r e have n o t been f u r t h e r f i e l d c o n t r o l f a i l u r e s due t o r e s i s t a n c e i n any o f t h e a r e a s where t h e program h a s been attempted, a l t h o u g h some i n c r e a s e i n r e s i s t a n c e has c o n t i n u e d i n a r e a s u s i n g t h e A u s t r a l i a n program ( B u l l and Menn, this vol.). The k e y t o s u c c e s s i n t h i s c a s e o f r e s i s t a n c e management has been t h e u n u s u a l l y h i g h l e v e l o f v o l u n t a r y cooperation. H o u s e f l i e s on D a n i s h farms have become r e s i s t a n t t o a l m o s t e v e r y new i n s e c t i c i d e i n t r o d u c e d f o r t h e i r c o n t r o l s i n c e t h e 1950's (36). I n t h e m i d 1970's, s c i e n t i s t s showed t h a t r e s i s t a n c e t o DDT and t h e new p y r e t h r o i d i n s e c t i c i d e s i s due t o a common r e s i s t a n c e f a c t o r ( t h e kdr and super-kdr g e n e s ) , and they p r e d i c t e d t h a t r a p i d r e s i s t a n c e development t o t h e more p e r s i s t e n t SP compounds would r a p i d l y evolve i n the f i e l d . I n 1978-79, s u r v e y s f o r SP r e s i s t a n c e i n d i c a t e d t h a t r e s i s t a n c e t o l o n g - r e s i d u a l compounds was b e g i n n i n g to develop i n the f i e l d . O v e r a l l , the survey data i n d i c a t e d that r e s i s t a n c e would soon be w i d e s p r e a d . S e v e r a l s t e p s were immediately taken t o evaluate the r e s i s t a n c e p o t e n t i a l o f

Species/ Prod. System

Tetranychus urticae/ pear-apple

Western USA, Australia

Monitoring, Rotations, Regulation, Industry Compliance/Difficult Biology, Chemical Alternatives

Western USA

Psylla pyricola/ pear

Monitoring, Unstable-, Croft et a l . 1987, Resistance Selective Edge & James 1986 Cpds, Rotations, Flexner 1988 Formulation, B i o l o g i c a l Control/ Grower Compliance

R i e d l et a l . 1981, Dover & C r o f t 1984, F o l l e t t et a l . 1985

Monitoring, Nonpersistent Keiding 1986 Compounds, Regulations/ Environmental Limitations

Denmark

Daly & McKenzie 1987 B u l l & Menn, t h i s v o l .

References

Musca domestica/ animals

Monitoring, Thresholds, Area-wide compliance

Recommended T a c t i c s / L i m i t i n g Factors

Australia

Site

Heliothis armigera/ cotton

More Successful:

Class

Table I. Case H i s t o r i e s of Pesticide Resistance Management Implementation

1

s

o n a

*

%

H O

w

i

2

Southern USA

Australia

Tropical areas

Italy, Eastern USA

Heliothis virescens/ cotton

Boophilus microplus/ cattle

Plutella xylostella/ vegetables

Psylla pyri/ Psylla pyrico1a/pear

Less Successful:

Pest/Natural USA Enemy Complex/ apple

Monitoring, Synergists/ No Rotation, no RM Program per se

Monitoring, C u l t u r a l & B i o l o g i c a l Controls/ B i o l o g i c a l Constraints, Low Thresholds

Monitoring, S t r a t e g i c Dipping, Grazing Mgmt./ Grower Compliance

Monitoring, Thresholds, Mixtures, Synergists/ Grower Apathy, Limited Compliance

Burts, E.C. pers. comm. 1988 Enduro Corp pers. comm. 1985

Tabashnik 1986b Tabashnik B.E., unpub. 1988

Sutherst & Comins 1979

Roush, R.T. unpub. 1988 Plapp & Campanhola 1986 B u l l & Menn, t h i s v o l . Riley, this v o l .

Monitoring, Lack of C r o f t 1982, Resistance i n Key Pests, C r o f t e t a l . 1984, Resistant N.E., S e l e c t i v e C r o f t e t a l . 1987 Pesticides, Biological Control/Grower Compliance, Improved Monitoring Methods

160


n o n p e r s i s t a n t SP's, and a d d i t i o n a l m o n i t o r i n g and r e g u l a t o r y a c t i o n s were implemented. A d e c i s i o n was made i n c o l l a b o r a t i o n w i t h s c i e n t i s t s , i n d u s t r y and r e g u l a t o r y p e r s o n n e l a g a i n s t r e g i s t e r i n g p e r s i s t e n t compounds. S t r i c t r e g u l a t i o n and m o n i t o r i n g o f SP r e s i s t a n c e was employed. So f a r , SP r e s i s t a n c e i n the c o u n t r y has been manageable. Through t h e s e a c t i o n s , c o n t i n u e d use o f t h e s e compounds has been s u s t a i n e d i n a v e r y d i f f i c u l t r e s i s t a n c e management environment. The keys t o t h i s c a s e h i s t o r y a r e the e f f e c t i v e n e s s o f the r e s i s t a n c e m o n i t o r i n g e f f o r t and the c r i t i c a l r e g u l a t o r y a c t i o n s taken to insure that c e r t a i n p e s t i c i d a l p r o d u c t s a r e n o t used. S u c c e s s f u l r e s i s t a n c e management i n the p e a r p s y l l a (Psylla pyrlcola) has i n v o l v e d c o n s e r v a t i v e p e s t i c i d e programs and c o o p e r a t i o n among i n d u s t r y and growers i n a t t e m p t i n g t o s o l v e a s e r i o u s r e s i s t a n c e problem. I n the p a s t , t h i s s p e c i e s has developed r e s i s t a n c e to v i r t u a l l y a l l p e s t i c i d e s r e g i s t e r e d f o r i t s c o n t r o l , o f t e n o v e r l a r g e a r e a s (37-38). I n the l a t e 1970's, e x p e r i m e n t s d e m o n s t r a t e d c o n c l u s i v e l y t h a t r e s i s t a n c e t o the SP's would o c c u r i f t h e s e p r o d u c t s were u s e d u n i l a t e r a l l y p r e b l o o m and d u r i n g m i d - s e a s o n f o r summer c o n t r o l o f t h i s p e s t ( 3 2 ) . A program o f SP use i n prebloom on o v e r w i n t e r i n g p s y l l a and the carbamate, a m i t r a z , i n summer was recommended. Growers r e a d i l y c o m p l i e d t o SP use r e s t r i c t e d i n t h i s manner. F u r t h e r m o r e , SP c h e m i c a l p r o d u c e r s d i d n o t p u t summer use on the l a b e l , thus making t h i s use o f SP's less likely. I n some p e s t management d i s t r i c t s , r e g u l a t o r y o f f i c i a l s , w i t h grower s u p p o r t , made summer use o f SP's an i l l e g a l p r a c t i c e , thus g o i n g one s t e p f u r t h e r i n i n s u r i n g t h a t misuse o f these products d i d not occur. To d a t e , SP r e s i s t a n c e has n o t d e v e l o p e d i n p s y l l a p o p u l a t i o n s i n a r e a s o f the w e s t e r n U n i t e d S t a t e s , where t h e s e s t r i c t l i m i t s have been promoted. In c o n t r a s t , i n a r e a s where SP's a r e use i n the summer, r e s i s t a n c e i n P. pyrlcola and a r e l a t e d s p e c i e s (Psylla pyri) has d e v e l o p e d r a p i d l y (see b e l o w ) . The key t o s u c c e s s i n t h i s c a s e has been the f a r s i g h t e d r e s i s t a n c e r i s k assessment r e s e a r c h t h a t was i n i t i a l l y done and the e x c e l l e n t r e g u l a t o r y and i n d u s t r y c o o p e r a t i o n t h a t h e l p e d m a i n t a i n the program. A n o t h e r s u c c e s s i n r e s i s t a n c e management i n v o l v e s n o t j u s t a s i n g l e key p e s t s p e c i e s , b u t a whole complex o f phytophagous a r t h r o p o d p e s t s o f a p p l e i n the U n i t e d S t a t e s ( 3 9 ) . I t also f o c u s e s on r e s i s t a n c e management o f a number o f b e n e f i c i a l a r t h r o p o d p r e d a t o r s and p a r a s i t o i d s t h a t p r o v i d e s i g n i f i c a n t b i o l o g i c a l c o n t r o l o f a v a r i e t y o f s e c o n d a r y p e s t s on t h i s c r o p . I n t h i s c a s e , a r a t h e r s e r e n d i p i t o u s p a t t e r n o f r e s i s t a n c e has d e v e l o p e d among s p e c i e s t o c e r t a i n organophosphate (OP) insecticides. T h i s r e s i s t a n c e o r l a c k t h e r e o f i n some s p e c i e s has been e x p l o i t e d , p r o v i d i n g an example o f IPM, as w e l l as r e s i s t a n c e management. To summarize the r e s i s t a n c e s i t u a t i o n i n b r o a d terms, no key p e s t such as the c o d l i n g moth, a p p l e maggot, plum c u r c u l i o has d e v e l o p e d r e s i s t a n c e t o the OP a z i n p h o s m e t h y l , whereas a v a r i e t y o f s e c o n d a r y p e s t s such as m i t e s , a p h i d , l e a f h o p p e r s , l e a f m i n e r s and t h e i r n a t u r a l enemies have d e v e l o p e d r e s i s t a n t s t r a i n s ; thus a z i n p h o s m e t h y l has become more s e l e c t i v e . The example c i t e d l a t e r o f management o f c y h e x a t i n r e s i s t a n c e management i n the s p i d e r m i t e

10.

CROFT


161

T. urticae u s i n g b i o l o g i c a l c o n t r o l by i n s e c t i c i d e - r e s i s t a n t p r e d a t o r y m i t e s i s j u s t a subsystem o f t h i s l a r g e r r e s i s t a n c e management program. E s s e n t i a l management components o f the program i n c l u d e : 1) c a r e f u l m o n i t o r i n g f o r OP r e s i s t a n c e i n key p e s t s such as the c o d l i n g moth, a p p l e maggot, plum c u r c u l i o , and s e v e r a l l e a f r o l l e r s p e c i e s ; 2) s e e k i n g t o m i n i m i z e f u r t h e r r e s i s t a n c e development i n s e c o n d a r y p e s t s such as m i t e s , a p h i d s , l e a f m i n e r s , l e a f h o p p e r s and s c a l e s t h r o u g h minimum use o f s e l e c t i v e p e s t i c i d e s and maximum e x p l o i t a t i o n o f b i o l o g i c a l c o n t r o l a g e n t s ; and 3) s e e k i n g t o e x p l o i t r e s i s t a n c e i n key n a t u r a l enemy s p e c i e s by m o n i t o r i n g f o r n a t u r a l development o f r e s i s t a n c e o r by g e n e t i c improvement o f r e s i s t a n t s t r a i n s using h y b r i d i z a t i o n or a r t i f i c i a l s e l e c t i o n techniques. The s u c c e s s o f the r e s i s t a n c e management program f o r the complex o f p e s t s and n a t u r a l enemies o f a p p l e i n the U n i t e d S t a t e s , w h i l e g e n e r a l l y good, has been mixed. I n some a r e a s o f the e a s t e r n U n i t e d S t a t e s where OP r e s i s t a n c e has d e v e l o p e d i n key l e a f r o l l e r s p e c i e s , i n c r e a s e d use o f n o n s e l e c t i v e p e s t i c i d e s such as the p y r e t h r o i d s has o c c u r r e d . However, i n the w e s t e r n U n i t e d S t a t e s , OP p e s t i c i d e s s t i l l p r o v i d e adequate c o n t r o l o f key p e s t s , w h i l e n o t u p s e t t i n g b i o l o g i c a l c o n t r o l o f c e r t a i n s e c o n d a r y p e s t s by t h e i r r e s i s t a n t p r e d a t o r s and p a r a s i t e s ( 3 9 ) . I n t h o s e a r e a s where the program i s s u c c e s s f u l , the keys t o s u c c e s s a r e m o n i t o r i n g f o r r e s i s t a n c e i n the s p e c i e s complex ( e . g . , among l e a f r o l l e r s , 40), r a p i d r e s p o n s e t o e a r l y s i g n s o f r e s i s t a n c e ( e . g . , 41)> maximum use o f IPM and a l t e r n a t i v e c o n t r o l t a c t i c s o t h e r t h a n p e s t i c i d e s (42), and the l a c k o f r e s i s t a n c e development i n key p e s t s s u c h as the c o d l i n g moth. L e s s S u c c e s s f u l R e s i s t a n c e Management. P y r e t h r o i d r e s i s t a n c e i n N o r t h American Heliothis spp. has been o f g r e a t c o n c e r n t o s c i e n t i s t s s i n c e t h e s e p e s t i c i d e s were f i r s t i n t r o d u c e d i n the l a t e 1970's ( B u l l and Menn, R i l e y , t h i s v o l . ) . However, many c o t t o n growers i n i t i a l l y were unconcerned, a p p a r e n t l y out o f a f a i t h t h a t p e s t i c i d e m a n u f a c t u r e r s would c o n t i n u e t o d e v e l o p r e p l a c e m e n t compounds. I n s p i t e o f the e f f o r t s o f c o t t o n e n t o m o l o g i s t s t o promote j u d i c i o u s use o f the SP's i n the 1970's, t h e r e was a tendency t o use t h e s e c h e m i c a l s i n t e n s i v e l y . Not s u r p r i s i n g l y , and w i t h s t r i k i n g p a r a l l e l s t o the A u s t r a l i a n s i t u a t i o n , r e s i s t a n c e as m a n i f e s t e d by c o n t r o l f a i l u r e s appeared i n Heliothis virescens in c e r t a i n a r e a s o f w e s t e r n Texas i n 1985 ( 4 3 ) . R e s i s t a n c e i n Texas was c o n f i r m e d by Roush & L i t t r e l l (44), who a l s o documented the i n d e p e n d e n t e v o l u t i o n o f r e s i s t a n c e i n M i s s i s s i p p i i n 1986. More r e c e n t l y , SP r e s i s t a n c e i n H. virescens has a p p e a r e d i n a number o f c o t t o n p r o d u c t i o n a r e a s t h r o u g h o u t the s o u t h e r n U n i t e d S t a t e s ( B u l l and Menn, R i l e y ; t h i s v o l . ) An i n i t i a l r e s i s t a n c e management program was d e v e l o p e d by e n t o m o l o g i s t s f o r M i s s i s s i p p i , L o u i s i a n a , and A r k a n s a s growers, b u t i n i t i a l l y i t was o n l y recommended t o growers. I n the absence o f some enforcement o r u n l e s s the r e s i s t a n c e problems becomes more s e v e r e , i t i s p r o j e c t e d t h a t the program w i l l n o t be w i d e l y adopted. A l a r g e r consensus o f i n d u s t r y , p u b l i c and p r i v a t e groups i s needed t o j o i n i n s u p p o r t i n g such a program. E i t h e r a v o l u n t a r y p o l i c y o f c o m p l i a n c e o r a mandated one

162


s i m i l a r to t h a t used f o r s t a l k d e s t r u c t i o n of p l a n t r e s i d u e s i s needed t o l i m i t f u r t h e r r e s i s t a n c e development i n t h e s e key c o t t o n pests. Another case h i s t o r y o f l i m i t e d progress i n s p i t e of extensive r e s e a r c h on r e s i s t a n c e management i n v o l v e s the c a t t l e t i c k Boophilus microplus i n A u s t r a l i a . P a r t i c u l a r l y i n southeastern Queensland, t h i s s p e c i e s has been a c r i t i c a l t h r e a t t o the c a t t l e i n d u s t r y p r i m a r i l y because o f the i n a b i l i t y t o c o n t r o l i t due t o r e s i s t a n c e (45). C o n s i d e r a b l e e f f o r t has been d e v o t e d t o r e s i s t a n c e s t u d i e s , and A u s t r a l i a n t i c k r e s i s t a n c e a u t h o r i t i e s now b e l i e v e t h e y have some v e r y c l e a r i d e a s on how r e s i s t a n c e can be d e l a y e d ( J . Nolan, remarks a t a CSIRO/DSIR Workshop). Many o f t h e s e c o n c e p t s were p r e v i o u s l y d e s c r i b e d and a n a l y z e d i n m o d e l i n g s t u d i e s o f S u t h e r s t & Comins ( 4 5 ) . However, A u s t r a l i a n c a t t l e p r o d u c e r s a r e a l e s s c o h e s i v e group t h a n A u s t r a l i a n c o t t o n growers. W h i l e the A u s t r a l i a n c o t t o n i n d u s t r y i s o n l y about 20 y e a r s o l d , c a t t l e p r o d u c t i o n has been a major e n t e r p r i s e f o r more t h a n 100 y e a r s , and many p r o d u c t i o n p r a c t i c e s are s t r o n g l y i n f l u e n c e d by t r a d i t i o n a l approaches t o management. Where the c o t t o n growers, perhaps r a t h e r u n i q u e l y i n A u s t r a l i a n a g r i c u l t u r e , t e n d t o band t o g e t h e r , c a t t l e p r o d u c e r s t e n d t o be v e r y i n d e p e n d e n t , and t h e y a r e slow t o adopt new r e s i s t a n c e management methods. The diamondback moth (Plutella xylostella) i s a major p e s t o f c r u c i f e r o u s v e g e t a b l e s i n more t h a n 80 c o u n t r i e s , w o r l d w i d e . It has d e v e l o p e d r e s i s t a n c e to a l l major c l a s s e s o f i n s e c t i c i d e s ( 4 6 ) . T h r e e f a c t o r s promote i t s r a p i d e v o l u t i o n o f r e s i s t a n c e t o p e s t i c i d e s : 1) i t s b i o l o g y , 2) the r e l a t i v e l y low l e v e l o f a c c e p t a b l e damage, and 3) the i n t e n s i v e use o f i n s e c t i c i d e s n e c e s s a r y f o r i t s c o n t r o l (47). I n t r o p i c a l r e g i o n s t h i s p e s t can complete more t h a n 15 g e n e r a t i o n s y e a r l y , w h i c h a c c e l e r a t e s r e s i s t a n c e development (11). Because o f the d i r e c t use o f the c r o p f o r human consumption, the economic t h r e s h o l d f o r c o n t r o l i s o n l y 1-2 l a r v a e p e r p l a n t . I n s e c t i c i d e s have been u s e d h e a v i l y f o r diamondback moth c o n t r o l . For example, many f a r m e r s i n Taiwan s p r a y weekly f o r c o n t r o l . C o n s e q u e n t l y , more t h a n 2 0 0 0 - f o l d r e s i s t a n c e t o the p y r e t h r o i d i n s e c t i c i d e s has d e v e l o p e d l e s s t h a n f o u r y e a r s a f t e r i n i t i a l use o f t h e s e p r o d u c t s ( 4 7 ) . Simulation studies s u g g e s t t h a t under t r o p i c a l c o n d i t i o n s , i n s e c t i c i d e use must be r e d u c e d t o two o r fewer s p r a y s p e r c r o p c y c l e t o s u b s t a n t i a l l y slow r e s i s t a n c e development (48). A l t h o u g h t h i s moth can d i s p e r s e g r e a t d i s t a n c e s , some l o c a l v a r i a t i o n i n r e s i s t a n c e development among i n d i v i d u a l p o p u l a t i o n s does o c c u r . This suggests that i n d i v i d u a l growers c o u l d r e t a r d r e s i s t a n c e development i n t h e i r own f i e l d s by r e d u c i n g i n s e c t i c i d e use. I n t e g r a t i o n o f i n s e c t i c i d e s w i t h b i o l o g i c a l , c u l t u r a l , and m i c r o b i a l methods f o r diamondback moth c o n t r o l i s the most p r o m i s i n g way t o r e t a r d r e s i s t a n c e development. However, i m p l e m e n t a t i o n o f t h e s e methods i s complex and d i f f i c u l t t o a c h i e v e w i t h growers ( T a b a s h n i k , B.E., p e r s . c o r r e s p . , 1988). A f i n a l example o f where l i t t l e p r o g r e s s has been made i n a c h i e v i n g r e s i s t a n c e management i s w i t h the p e a r p s y l l a i n p a r t s o f Europe ( T a b l e I). As n o t e d e a r l i e r , i n a r e a s where b o t h pre-bloom and summer a p p l i c a t i o n s o f p y r e t h r o i d i n s e c t i c i d e s have been u s e d u n i l a t e r a l l y , r e s i s t a n c e t o the SP has d e v e l o p e d w i d e l y .

10. CROFT


P o l i c y and P e s t i c i d e R e s i s t a n c e

163

Management

S e v e r a l g e n e r a l i z a t i o n s c a n be made from t h e c a s e h i s t o r i e s c i t e d above. They a p p l y i n many c a s e s t o t h e b a s i c and a p p l i e d r e s e a r c h gaps d i s c u s s e d e a r l i e r . I n other cases, i t i s antiquated p o l i c i e s that l i m i t greater implementation o f p e s t i c i d e r e s i s t a n c e management. Policy i s a recommended c o u r s e o f a c t i o n f o l l o w e d by a p e r s o n , group o r i n s t i t u t i o n t h a t i s s e l e c t e d from a l t e r n a t i v e s i n l i g h t o f g i v e n c o n d i t i o n s t o g u i d e and determine p r e s e n t and f u t u r e decisions. A v a r i e t y o f p o l i c y i s s u e s and c o n s t r a i n t s have been r a i s e d by academic, government, i n d u s t r y and p u b l i c groups i n t e r e s t e d i n f a c i l i t a t i n g greater implementation o f r e s i s t a n c e management i n t h e f i e l d (12,14,49). A c o m p a r a t i v e l i s t o f p o l i c y f a c t o r s i d e n t i f i e d by two s t u d y groups who c o n s i d e r e d t h e s e i s s u e s as t h e y o p e r a t e i n the U n i t e d S t a t e s i s shown i n T a b l e I I . Many common i s s u e s were i d e n t i f i e d by b o t h groups. Table I I . Issues Areas o f Resistance

P o l i c y Issue Area/Topic

2

Management P o l i c y

P o l i c y Study Group/Importance Rating"^" _________________ Dover & C r o f t

(1984)

NAS

Information Storage, R e t r i e v a l , & Dissemination

X X X

X X X

International Coordination and P o l i c y

X

X X X

R e g u l a t o r y Reform/ Federal

X X X

XX

R e g u l a t o r y Reform/ State & Local

X X X

XX

Industry

Self-Regulation

X X X

X X X

Industry

Marketing

X X X

XX

X

XX

XX

X X X

Antitrust Limitations Implementation Infrastructure

(1986)

XXX = g r e a t importance, XX - moderate importance, X l i t t l e importance. See Dover & C r o f t (14) and NAS (12) f o r e x p l a n a t i o n of these t i t l e s . P o l i c y f o r r e s i s t a n c e management i n v o l v e s a s p e c t s o f p e s t i c i d e r e g u l a t i o n , m a r k e t i n g , a n t i t r u s t , i n t e r n a t i o n a l c o n s i d e r a t i o n s and education (TableII). Due t o time and space l i m i t a t i o n s , each o f t h e s e t o p i c s c a n n o t d i s c u s s e d h e r e , b u t s e v e r a l were r e f e r r e d t o

164


i n T a b l e I. F o r a more complete t r e a t m e n t o f p o l i c y and r e s i s t a n c e management, see (14) and ( 1 2 ) . P o l i c y i s u s u a l l y i n v o l v e d i n most a t t e m p t s t o implement r e s i s t a n c e management programs. I n f a c t , p o l i c y i s more o f t e n a c o n s t r a i n t t o r e s i s t a n c e management t h a n r e s e a r c h l i m i t a t i o n s . Many p o l i c i e s must be u p d a t e d i f the environment f o r r e s i s t a n c e management approaches i s t o be improved. New p o l i c i e s o f r e s i s t a n c e management a r e b e g i n n i n g t o be d e v e l o p e d w i t h r e g a r d t o a c a r i c i d e r e s i s t a n c e problems on d e c i d u o u s t r e e f r u i t s (42). Changes i n p e s t i c i d e i n d u s t r y p o l i c i e s have enhanced o p p o r t u n i t i e s to implement r e s i s t a n c e management i n the field. R e s i s t a n c e management w i t h the s p i d e r m i t e Tetranychus urticae t o o r g a n o t i n (OT) and s e v e r a l new a c a r i c i d e s i n v o l v e s s e v e r a l p h y s i o l o g i c a l l y s e l e c t i v e compounds which a l l o w f o r i n c r e a s e d b i o l o g i c a l c o n t r o l by i n s e c t i c i d e - r e s i s t a n t p r e d a t o r y mites (42). I n s t u d i e s made i n the w e s t e r n U n i t e d S t a t e s and A u s t r a l i a , r e s e a r c h e r s demonstrated t h a t c y h e x a t i n r e s i s t a n c e r a p i d l y r e v e r t s toward s u s c e p t i b i l i t y i n the absence o f i n t e n s e s e l e c t i o n by the o r g a n o t i n s o r o t h e r c r o s s - r e s i s t a n t a c a r i c i d e s (50-51). A l s o , a number o f t a c t i c s a r e a v a i l a b l e t o l i m i t OT r e s i s t a n c e i n c l u d i n g : f o r m u l a t i o n s t h a t e f f e c t i v e l y enhance t o x i c i t y to r e s i s t a n t m i t e s (50-51), c r i t i c a l t i m i n g o f o r g a n o t i n a p p l i c a t i o n s t o c o n t r o l more s u s c e p t i b l e immature m i t e s t a g e s (42.50-51). a l t e r n a t i o n o f o r g a n o t i n s w i t h n o n c r o s s - r e s i s t a n t a c a r i c i d e s (42,51), and i n c r e a s e d use o f p r e d a t o r s i n b i o l o g i c a l c o n t r o l ( 4 2 ) . Using a c o m b i n a t i o n o f t h e s e measures a l l o w s f o r c o n t i n u e d use o f the o r g a n o t i n s i n a r e a s where p r e v i o u s use was l i m i t e d due t o the presence of h i g h l y r e s i s t a n t mites. The key t o s u c c e s s i n t h i s c a s e has been the i n s t a b i l i t y o f OT r e s i s t a n c e i n s p i d e r m i t e s , the wide v a r i e t y o f a l t e r n a t i v e t o o l s a v a i l a b l e t o combat r e s i s t a n c e development, and the e x t e n s i v e r e s e a r c h e f f o r t made t o i n t e g r a t e t h e s e methods. W h i l e p r o g r e s s i n p r e s e r v i n g the o r g a n o t i n s was made a f t e r r e s i s t a n c e d e v e l o p e d , s i g n i f i c a n t s t e p s have a l s o been t a k e n t o p r e v e n t r e s i s t a n c e from d e v e l o p i n g t o s e v e r a l new s e l e c t i v e a c a r i c i d e s , b e f o r e t h e i r r e g i s t r a t i o n f o r f i e l d use ( 4 2 ) . The s t i m u l u s f o r new p o l i c y has come from an i n d i c a t i o n o f h i g h r e s i s t a n c e r i s k t o the o v i c i d e s , h e x y t h i a z o x and c l o f e n t e z i n e . In e x p e r i m e n t a l s t u d i e s i n greenhouses i n A u s t r a l i a , c i t r u s p l o t s i n J a p a n and a p p l e o r c h a r d s i n S p a i n , r e s i s t a n c e to h e x y t h i a z o x and i n some c a s e s , c r o s s - r e s i s t a n c e t o c l o f e n t e z i n e was n o t e d a f t e r o n l y 15-25 s e l e c t i o n s . A t the i n i t i a t i v e o f i n d u s t r y , cooperative r e s i s t a n c e management r e s e a r c h t r i a l s were u n d e r t a k e n a t s e v e r a l u n i v e r s i t i e s i n the U n i t e d S t a t e s t o d e v e l o p m o n i t o r i n g methods and t o e v a l u a t e the g e n e t i c s o f r e s i s t a n c e and o p e r a t i o n a l a l t e r n a t i v e s t o the use o f t h e s e a c a r i c i d e s . F u r t h e r m o r e , use o f t h e s e compounds was recommended o n l y once p e r s e a s o n on l a b e l s , and b o t h p a r e n t companies a g r e e d t h a t use o f the e i t h e r company's p r o d u c t would make subsequent use o f e i t h e r p r o d u c t u n d e s i r a b l e . Thus a c a u t i o n a r y s t a t e m e n t i n d i c a t i n g t h i s c r o s s - r e s i s t a n c e p o t e n t i a l was s t a t e d on the l a b e l o f b o t h compounds. These f a r - s i g h t e d p o l i c e s by i n d u s t r y a r e examples o f the t y p e s o f a c t i o n s t h a t are needed t o p r e v e n t o r stem the t i d e o f

10. CROFT


165

i n c r e a s i n g r e s i s t a n c e t o p e s t i c i d e s among a r t h r o p o d p e s t s . Such a c t i o n s show t h a t t h e l o n g e r term p e r s p e c t i v e s o f p r o d u c t c o n s e r v a t i o n and economic performance a r e more w i d e l y r e c o g n i z e d by r e s e a r c h , management and m a r k e t i n g p e r s o n n e l from i n d u s t r y . A t l e a s t f o r a c a r i c i d e s , these a c t i o n s a r e e s s e n t i a l f o r conserving f u t u r e p r o d u c t s c o n s i d e r i n g the h i g h c o s t s r e q u i r e d t o b r i n g a new p e s t i c i d e t o market and t h e s h o r t time t h e y may l a s t due t o r e s i s t a n c e problems. S i m i l a r a c t i o n s may be a p p r o p r i a t e f o r o t h e r r e s i s t a n c e - p r o n e p e s t i c i d e s and p e s t s p e c i e s . Summary G r e a t e r e f f o r t i s needed t o b u i l d management systems t h a t h e l p l i m i t development o f r e s i s t a n c e t o new p e s t i c i d e s as w e l l as t o c o n s e r v e o t h e r v a l u a b l e t a c t i c s o f p e s t c o n t r o l , s u c h as p e s t r e s i s t a n t h o s t p l a n t s and even some b i o l o g i c a l c o n t r o l a g e n t s ( C r o f t e t a l . 1988). Such e f f o r t w i l l be r e q u i r e d f o r g e n e t i c a l l y improved forms o f t h e s e p e s t c o n t r o l a g e n t s , as w e l l . E f f e c t i v e management systems s h o u l d be p u t i n p l a c e b e f o r e t h e s e new t a c t i c s o f p e s t c o n t r o l a r e d e p l o y e d r a t h e r t h a n a f t e r problems o f p e s t a d a p t a t i o n t o them a r e d e t e c t e d i n t h e f i e l d . I n d e v e l o p i n g p e s t i c i d e r e s i s t a n c e management systems, more e x p e r t i s e , t r a i n i n g and methodology a r e needed i n t h e e c o l o g y and population genetics of p e s t i c i d e resistance. This i s a c r i t i c a l gap r e s e a r c h needs. Many avenues c o u l d be p u r s u e d t o s o l v e t h e p r o b l e m o f g r e a t e r e x p e r t i s e i n t h e s e a r e a s , r a n g i n g from b e t t e r t r a i n i n g o f a p p l i e d s c i e n t i s t s , t o b e t t e r c o o p e r a t i o n between a p p l i e d and b a s i c s c i e n t i s t s t o i n c r e a s e d use o f r e s i s t a n c e models for evolutionary biology studies. Funding f o r research across m u l t i p l e d i s c i p l i n e s i s a key element i n b r i d g i n g t h i s gap. New i n s t i t u t i o n a l p o l i c i e s o f c o o p e r a t i o n and change a r e needed t o b e t t e r f a c i l i t a t e t h e i m p l e m e n t a t i o n o f r e s i s t a n c e management t a c t i c s a c r o s s b r o a d b o u n d a r i e s o f s o c i e t a l groups i n c l u d i n g p r o d u c e r s , i n d u s t r y p e r s o n n e l , r e g u l a t o r s , and p e s t i c i d e u s e r s . F o r example, r e s i s t a n c e management d i s t r i c t s c o u l d be o r g a n i z e d t o o p e r a t e much l i k e mosquito abatement d i s t r i c t s ( o r s i m i l a r u n i t s o f management) t h a t a r e e s t a b l i s h e d , a t l e a s t t e m p o r a r i l y , t o s o l v e a p e r s i s t e n t problem. IPM d i s t r i c t s o p e r a t e i n many r e g i o n s where p r o d u c e r s see a common b e n e f i t from o r g a n i z i n g t h e m s e l v e s . Most c a s e s o f r e s i s t a n c e management a r e u n i q u e i n terms o f what an a p p r o p r i a t e o r g a n i z a t i o n a l s t r u c t u r e might be. Each r e s i s t a n c e episode r e q u i r e s a very s p e c i f i c , t a i l o r e d response. Little effort has been made t o s t u d y how t o improve t h e i m p l e m e n t a t i o n o f r e s i s t a n c e management i n t h e f i e l d . Research, extension, p r i v a t e groups and o t h e r i n t e r e s t e d p e r s o n n e l must u n i t e t o d e v e l o p i n n o v a t i v e i d e a s on how t h e s e problems c a n be d e a l t w i t h i n t h e future. F i n a l l y , a Utopian g o a l f o r r e s i s t a n c e management would be t o stem t h e i n c r e a s i n g t i d e o f r e s i s t a n c e t o most c h e m i c a l p e s t c o n t r o l products. I n s t e a d o f e x p e r i e n c i n g an e f f e c t i v e l i f e o f 515 y e a r s u n t i l a compound i s r e n d e r e d i n e f f e c t i v e , we might see t h e s e p r o d u c t s l a s t f o r l o n g e r p e r i o d s - - u p t o 50 y e a r s o r more-under a b e t t e r r e s i s t a n c e management s c e n a r i o . T h i s would a l l o w time t o d e v e l o p o t h e r , more s a f e and e f f e c t i v e p r o d u c t s . Too o f t e n


166

in the past the obituary of a particular product has not been written by us, but by our competitors, the pests, as they have continued to find new ways to evolve resistant strains and circumvent our best efforts to contain them. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.

Brown, A. W. A. In Pesticides in the Environment; R. WhiteStevens, Ed.; Marcel Dekker: New York, 1971; Vol. 1, Part II, p. 457-552. Georghiou, G. P. Residue Rev. 1980, 76, 131-145. Roush, R. T.; McKenzie, J. Ann. Rev. Entomol. 1986, 32, 361380. Patton, S.; Craig, I. A.; Conway, G. R. In Pesticide Resistance and World Food Production; G. R. Conway, Ed.; Imperial College Centre Environ. Tox. U.K., 1982; p. 61-76. van den Bosch, R.; Stern, V. M. Ann. Rev. Entomol. 1962, 7, 367-386. Georghiou, G. P.; Taylor, C. E. J . Econ. Entomol. 1977a, 70, 319-323. Georghiou, G. P.; Taylor, C. E. J . Econ. Entomol. 1977b, 70, 653-658. Comins, H. N. J . Theor. Biol. 1977, 64, 177-197. Plapp, F. W. Jr.; Browning, C. R.; Sharp, P. J . Environ. Entomol. 1979, 8, 69-80. Wood, R. J . Parasitology 1981, 82, 69-80. Tabashnik, B. E . ; Croft, B. A. Environ. Entomol. 1982, 11, 1137-1144. Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington DC, 1986; 471 pp. Georghiou, G. P.; Saito, T. Eds. Pest Resistance to Pesticides; Plenum Press: New York, 1983; 809 pp. Dover, M. J.; Croft, B. A. World Res. Inst. Policy Paper, Nov. 1984; 80 pp. Hammock, B. D.; Soderlund, D. M. In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 111-129. Ozaki K. In Pesticide Resistance to Pesticides; G. P. Georghiou & T. Saito, Eds.; Plenum Press: New York, 1983; p. 595-614. Mullin C. A.; Croft, B. A. In Biological Control of Agricultural Integrated Pest Management Systems; M. A. Hoy & D. C. Herzog, Eds.; Academic: New York, 1985; p. 123-150. Brown, T. M.; Brogdon, N. Ann. Rev. Entomol. 1987, 32, 145162. Mouches, C. D.; Fournier, D.; Raymond, M.; Magnin, M.; Berge, J . B.; Pasteur, N.; Georghiou, G. P. Comptes Rendu Acad. Sci. Paris. Ser. III, 1985, 301, 695-700. Mouches, C.; Pasteur, N.; Berge, J . B.; Hyrien, O.; Raymond, M.; de Saint Vincent, B. R.; de Silvestri, M.; Georghiou, G. P. Science 1986, 233, 778-780. Georghiou, G. P. Ann. Rev. Ecol. Sys. 1972, 3, 133-168.

10. CROFT 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42.


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Georghiou, G. P.; Taylor, C. E. In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 143-156. Tabashnik, B. E . ; Croft, B. A. Entomophaga 1985, 30, 37-49. Roush, R. T.; Croft, B. A. In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 257-270. May R. M.; Dobson, A. P. In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 170-193. Tabashnik, B. E. In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 194-206. Uyenoyama, M. K. In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 207-221. Via, S. In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 222-235. Taylor, C. E. 1983. In Pest Resistance to Pesticides; G. P. Georghiou & T. Saito, Eds.; Plenum Press: New York, 1983; p. 163-173. Plapp, F.W. J r . In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 74-86. Rabb, R. L . ; Kennedy, G. G. Movement of Highly Mobile Insects: concepts and Methodology in Research; N. Carolina. St. Univ. Press: Raleigh, NC, 1979; 456 p. Roush, R. T.; Miller, G. L. J . Econ. Entomol. 1986, 79, 293298. Croft, B. A. (Leader). 1986. Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 271-278. Croft, B. A. Proc. CIPM IPM Project; R. F. Frisbie & P. L. Adkisson, Eds; Texas Agric. Exper. Sta. Press: College Station, TX, 1986. Daly, J . C.; McKenzie, J. A. Proc. British Crop Prot. Meeting, Bristol, UK, 1987. Keiding, J . In Pesticide Resistance: Strategies and Tactics for Management; National Academy Press: Washington, DC, 1986; p. 279-297. Riedl, H.; Westigard, P. H.; Bethell, R. S.; DeTar, J . E. Calif. Agric. 1981, 35, 7-9. Follett, P. A.; Croft, B. A.; Westigard, P. H. Can. Entomol. 1985, 117, 565-573. Croft, B. A. Entomol. Exper. & Appl. 1982, 31, 88-110. Croft, B. A.; Hull, L. A. In Tortricoid Pests; L.P.S. van der Geest and H. H. Evenhius, Eds.; Elsevier: Amsterdam, The Netherlands, 1988; (in press). Croft, B. A.; Miller, R. W.; Nelson, R. D.; Westigard, P. H. J . Econ. Entomol. 1984, 77, 574-578. Croft, B. A.; Hoyt; S. C.; Westigard, P. H. J . Econ. Entomol. 1987, 80, 304-311.

168 43. 44. 45. 46. 47. 48. 49. 50. 51.

MANAGING

RESISTANCE

TO

AGROCHEMICALS

Plapp, F. W. Jr.; Campanhola, C. Proc. 1986 Beltwide Cotton Res. Conf., 1986, p. 167-169. Roush, R. T.; L i t t r e l l , R. G. Proc. 1987 Beltwide Cotton Res. Conf., 1987. Sutherst, R. W.; Comins, H. N. Bull. Entomol. Res. 1979, 69, 519-537. Georghiou, G. P. FAO, Rome, Italy, 1981. Liu, M. Y.; Tzeng, Y. J.; Sun, C. N. J . Econ. Entomol. 1981, 74, 393-396. Tabashnik, B. E. J . Econ. Entomol. 1986, 79, 1447-1451. Dover M. J.; Croft, B. A. Bioscience 1986, 36, 78-85. Edge, V. E . ; James, D. G. J . Econ. Entomol. 1986, 79, 14771483. Flexner, J . L. Ph.D Thesis, Oregon State University, Corvallis, OR, 1988

RECEIVED October 20, 1989

Management of Pesticide Resistance in Arthropod Pests - ACS

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