Advances in Pesticide Formulation Technology - American Chemical

10 Microencapsulated Pesticides and Their Effects on Non-Target Insects G. H. DAHL and J. R. LOWELL, JR. Downloaded by OHIO STATE UNIV LIBRARIES on March 15, 2013 | http://pubs.acs.org Publication Date: June 5, 1984 | doi: 10.1021/bk-1984-0254.ch010

Pennwalt Corporation, Philadelphia, PA 19102

Recent studies indicate that microencapsulated insecticides do not represent a unique or special hazard to beneficial insects, in particular bees. It has been found that not only microencapsulated methyl parathion but also emulsifiable concentrate formulations of various pesticides are carried back to hives by bees approximately in proportion to their rates of application. Field studies involving blooming crops have demonstrated that in many instances the microencapsulated methyl parathion is less hazardous to bees than the corresponding emulsifiable concentrate. This hazard can be further reduced by the addition of certain adjuvants of the "sticker" type which in experimental studies has resulted in 50 to 90 percent reductions in bee mortality. Numerous field observations on various crops have shown that microencapsulated methyl parathion frequently has a minimal adverse effect on entomophagous insects. The widely used organophosphate i n s e c t i c i d e methyl p a r a t h i o n was the f i r s t m a t e r i a l to be formulated as a microencapsulated p e s t i c i d e . T h i s f o r m u l a t i o n , s o l d under the tradename PENNCAP-M I n s e c t i c i d e (a r e g i s t e r e d trademark of Pennwalt C o r p o r a t i o n ) , c o n s i s t s of nylon-type microcapsules which c o n t a i n the a c t i v e i n g r e d i e n t . The capsules a r e suspended i n water and t y p i c a l l y have an average p a r t i c l e s i z e of approximately 25 microns ( f i f t y percent by weight of the capsules have a p a r t i c l e s i z e of 25 microns or more). Upon a p p l i c a t i o n by conventional spray equipment the water evaporates, and the a c t i v e i n g r e d i e n t i s slowly r e l e a s e d over an extended p e r i o d of time.

0097-6156/ 84/ 0254-0141 $06.00/ 0 © 1984 American Chemical Society

In Advances in Pesticide Formulation Technology; Scher, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1984.

Downloaded by OHIO STATE UNIV LIBRARIES on March 15, 2013 | http://pubs.acs.org Publication Date: June 5, 1984 | doi: 10.1021/bk-1984-0254.ch010

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ADVANCES IN PESTICIDE FORMULATION TECHNOLOGY

By v i r t u e of t h e i r unique f o r m u l a t i o n , microencapsulated p e s t i c i d e s have s i g n i f i c a n t l y lower dermal and o r a l t o x i c i t i e s than the corresponding e m u l s i f i a b l e concentrate f o r m u l a t i o n s . Microencapsulated methyl p a r a t h i o n (MMP) was introduced commerc i a l l y i n 1974; i n 1976 and t h e r e a f t e r r e p o r t s of bee k i l l s a l l e g e d l y caused by t h i s product were p u b l i s h e d , p r i m a r i l y i n the news media and non-refereed j o u r n a l s . Claims were subsequently made that MMP i s c a r r i e d back t o the h i v e and i s uniquely hazardous because the s i z e o f the microcapsules i s i n the range of many p o l l e n s . Since many of the s t u d i e s reported were a f t e r the f a c t of bee k i l l s i t was u s u a l l y impossible to determine the c o n d i t i o n s at the time of the a p p l i c a t i o n , or even which of s e v e r a l i n s e c t i c i d e a p p l i c a t i o n s was r e s p o n s i b l e . We t h e r e f o r e undertook an extensive program to assess the hazard o f MMP to bees. Such r e s e a r c h was a l s o conducted by government agencies, e s p e c i a l l y the USDA. (Note: Some of the crops and a p p l i c a t i o n methods reported h e r e i n are not c o n s i s t e n t with the EPA-registered label. The crop a p p l i c a t i o n and methods employed were used s o l e l y to determine the nature and extent of the hazard and are not endorsed or recommended. The r e g i s t e r e d l a b e l should always be followed.) I n s e c t i c i d e Contamination

of Bee Hives

Our f i r s t o b j e c t i v e was t o determine whether microencapsulated methyl p a r a t h i o n i s unique i n i t s property to be c a r r i e d back to the h i v e by bees. To that end a mixture of three commonly used i n s e c t i c i d e s along with MMP was a p p l i e d t o a p l o t of blooming rape. The agents were azinphos-methyl (Guthion), parathion, and c a r b a r y l ( S e v i n ) . By using a mixture on a s i n g l e p l o t the e f f e c t s of v a r i a t i o n i n bee v i s i t a t i o n were e l i m i n a t e d and the tendencies to be c a r r i e d to the h i v e could be measured by the r e l a t i v e r e s i d u e l e v e l s i n the p o l l e n samples. F i v e a p p l i c a t i o n s were made over a p e r i o d of seventeen days. P o l l e n samples were c o l l e c t e d from h i v e s placed near the f i e l d a f t e r two, three, f o u r , and f i v e s u c c e s s i v e a p p l i c a t i o n s approximately two days a f t e r each a p p l i c a t i o n was made. The a p p l i c a t i o n r a t e s were doubled f o r the l a s t two a p p l i c a t i o n s . The data a r e shown i n Table I .


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DAHL AND LOWELL

Table I .

143

I n s e c t i c i d e Residues i n Rape P o l l e n Residues

(PP ) m


No. of Treatments 2 3 4(c) 5(c) a. b.

c.

MMP(a,b) 0.23 0.13 1.53 0.39

Parathion(b) 0.08 0.04 0.28 0.36

Azinphosmethyl (b) 0.59 0.33 0.71 0.26

Carbaryl (b) 0.39 0.35 0.60 1.2

PENNCAP-M I n i t i a l a p p l i c a t i o n r a t e s were 0.125, 0.36, 0.125, and 0.25 l b / a c r e of a c t i v e i n g r e d i e n t f o r MMP, parathion, azinphos-methyl, and c a r b a r y l , r e s p e c t i v e l y . A p p l i c a t i o n r a t e s were doubled.

Although the residues found cannot be c o r r e l a t e d with the a p p l i c a t i o n r a t e s , the r e s u l t s nevertheless demonstrate that a l l i n s e c t i c i d e s used i n t h i s t e s t were absorbed on the p o l l e n and c a r r i e d back t o the h i v e . These observations have been confirmed using other approaches by USDA and u n i v e r s i t y researchers at the U n i v e r s i t y of Wisconsin, who reported that f o r a g i n g bees have brought back t o t h e i r h i v e s permethrin, c a r b a r y l , and methyl parathion e m u l s i f i a b l e concentrate (MPEC) when a p p l i e d to shedding c o r n . ( l ) Another area o f concern i s the r e s i d u a l l i f e of a p e s t i c i d e once i t i s brought back t o the h i v e . Microencapsulated methyl parathion was a t one time b e l i e v e d t o represent a s p e c i a l hazard because o f i t s c o n t r o l l e d r e l e a s e f e a t u r e . Thus methyl parat h i o n from MMP was reported t o p e r s i s t i n stored p o l l e n f o r up to 17 months.(2) Unfortunately, l i t t l e i s known about the p e r s i s t e n c e o f i n s e c t i c i d e s i n honey bee combs and the subsequent e f f e c t s of t h e i r residues on the honey bees. Carbaryl has been shown t o p e r s i s t f o r a t l e a s t eight months i n c o l o n i e s (4) and permethrin f o r a t l e a s t seven months.(5) Recently, USDA researchers a t the U n i v e r s i t y of Wisconsin studied samples from two bee k i l l s that apparently involved methomyl and MMP a p p l i e d to sweet corn. Samples were c o l l e c t e d to determine, among others, whether methomyl p e r s i s t e d i n combs, A n a l y s i s demonstrated that e i g h t months a f t e r the i n s e c t i c i d e a p p l i c a t i o n , residues of 0.03 ppm of methyl parathion and 0.03 ppm of methomyl (5) remained, even though the l a t t e r i s c o n s i d ered t o be a s h o r t - r e s i d u a l p e s t i c i d e . In another study conducted by the Honey Bee Research Laboratory of the A g r i c u l t u r a l Research S e r v i c e i n Laramie, Wyoming, p o l l e n cake or d r y p o l l e n t r e a t e d with MPEC or MMP was



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fed long term a t low r a t e s i n s t u d i e s conducted i n 1979 and 1980.(6) At r a t e s o f 0.01, 0.1, and 1.0 ppm ( a c t i v e i n g r e d i e n t , a . i . ) no s i g n i f i c a n t m o r t a l i t y d i f f e r e n c e s were noted between the t r e a t e d p o l l e n and the c o n t r o l . At 10 ppm MMP there was s i g n i f i c a n t m o r t a l i t y , and three out of s i x c o l o n i e s died a f t e r 15 weeks; however, s i g n i f i c a n t l y higher m o r t a l i t y r e s u l t e d when MPEC was f e d a t that c o n c e n t r a t i o n . These r e s u l t s a r e s i g n i f i cant i n that i n numerous Pennwalt i n v e s t i g a t i o n s of bee l o s s e s where MMP use was a suspected cause, the residues of methyl p a r a t h i o n , i f found, were of the order of 1.0 ppm. The same authors conducted a s i m i l a r study w i t h carbofuran and found that a l l c o l o n i e s d i e d w i t h i n eight days when they were f e d sugar syrup c o n t a i n i n g 10 p a r t s per m i l l i o n o f that i n s e c t i c i d e . ( 7 ) Comparative Bee T o x i c i t y of I n s e c t i c i d e - T r e a t e d F i e l d s To i n v e s t i g a t e the t o x i c i t y of f i e l d - a p p l i e d MMP, USDA and Texas A&M researchers i n 1981 near Lubbock, Texas, t r e a t e d 10-acre p l o t s of sunflowers i n l a t e f u l l bloom w i t h MPEC and MMP, r e s p e c t i v e l y , ( 8 ) S i x c o l o n i e s o f bees were placed near each o f these f i e l d s as w e l l as near a t h i r d untreated f i e l d which was r e t a i n e d as a c o n t r o l . D a i l y c o l l e c t i o n s of dead bees and p o l l e n were made to monitor the t o x i c e f f e c t s of the i n s e c t i c i d e and to estimate l e v e l s of f o r a g i n g a c t i v i t y . The r e s u l t s a r e shown i n Table I I .

Table I I .

Before Treatment Total for Five Days A f t e r Treatment a. b.

Bee M o r t a l i t y - Sunflowers T o t a l No. of Dead Bees (six colonies) Untreated MMP(a,b) MPEC(b) Control 116 119 126 431

2760

11941

PENNCAP-M Application rate 1 l b a.i./acre

C l e a r l y , bee c o l o n i e s exposed i n t h i s t e s t to MMP s u f f e r e d only about one f o u r t h the damage experienced by the c o l o n i e s exposed to MPEC. Peak m o r t a l i t y f o r MPEC-treated p l o t s occurred on the f i r s t day and on the second day f o r the MMP. On the f i f t h day m o r t a l i t i e s were 45, 82, and 207 dead bees f o r the c o n t r o l , MMP, and an MPEC, r e s p e c t i v e l y . S i m i l a r l y , the amount of p o l l e n c o l l e c t e d from the f i e l d t r e a t e d with the MPEC was about 80% l e s s than the amount c o l l e c t e d from the MMP-treated p l o t .


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Methyl p a r a t h i o n r e s i d u e s i n trapped p o l l e n b e f o r e and f o r f i v e days a f t e r a p p l i c a t i o n were a l s o measured. No s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s were noted (Table I I I ) .

Table I I I .

Methyl P a r a t h i o n Residues i n Trapped - Sunflowers

Pollen


Residues (ppm) MPEC 0 1.94 0.73 0.19 0.16 0.08

Day 0 1 2 3 4 5

MMP 1.62 0.49 0.06 0.08 0.04

Recently researchers a t the P l a n t Science Research Laborat o r y o f the USDA i n Oklahoma examined the r e l a t i v e t o x i c i t y t o honey bees o f the two methyl p a r a t h i o n formulations when a p p l i e d to f l o w e r i n g a l f a l f a . ( 9 ) Three a e r i a l a p p l i c a t i o n s were made over a p e r i o d o f 21 days, two w i t h MMP and one w i t h MPEC. Bee m o r t a l i t y observed w i t h MMP one day a f t e r a p p l i c a t i o n was only 11 percent of that observed f o r MPEC. Over the four-day p e r i o d a f t e r a p p l i c a t i o n the t o t a l m o r t a l i t y i n the MMP p l o t was 22 percent of that i n the MPEC p l o t .

Table IV. Bee M o r t a l i t y From A p p l i c a t i o n of Methyl P a r a t h i o n Formulations to Blooming A l f a l f a

Days A f t e r Spray Pre-Spray 1 2 3 4 5 a. b.

Av. No. of Dead Bees (per hive) MMP(a,b) 15 ( 16) 287 (216) 307 (116) 90 ( - ) 65 (133) 35 ( 44)

MPEC 21 2608 262 219 198

PENNCAP-M F i g u r e s i n parentheses were obtained a f t e r a second application. _ _

Studies comparing MMP with other p e s t i c i d e s have a l s o shown that i t does not represent an unusual hazard t o bees. In Wisconsin a p p l i c a t i o n on pollen-shedding corn of c a r b a r y l plus p a r a t h i o n


146


i n e a r l y and standard treatments and of carbofuran a l l produced g r e a t e r bee m o r t a l i t y than d i d MMP.Q) C l e a r l y , the above data i n d i c a t e that microencapsulated p e s t i c i d e s do not n e c e s s a r i l y represent a unique hazard to bees, but, t o the c o n t r a r y , t h e r e i s evidence that t h i s hazard, a t l e a s t i n the case of methyl p a r a t h i o n , i s l e s s than f o r the e m u l s i f i a b l e concentrate on many crops.


Reduction of Bee M o r t a l i t y by Adjuvants Studies conducted by Pennwalt Corporation i n the past three years have i n d i c a t e d that the bee hazard of MMP may be f u r t h e r reduced by the a d d i t i o n o f c e r t a i n adjuvants. These a d d i t i v e s are b e l i e v e d t o be e f f e c t i v e by reducing the pick-up of contaminated p o l l e n by f o r a g i n g bees. Numerous s m a l l - p l o t f i e l d s t u d i e s were made by comparing bee m o r t a l i t y r e s u l t i n g from the a p p l i c a t i o n t o v a r i o u s blooming crops of MMP alone or with a s t i c k e r f o r m u l a t i o n added t o the spray. Reductions i n bee m o r t a l i t y from 55 t o 75% were noted (Table V ) .

~~

Table V.

Crop Buckwheat Buckwheat Safflower Mustard a. b. c.

Comparison of Bee M o r t a l i t y i n Small-Plot Tests on Blooming Crops - MMP v s . MMP P l u s S t i c k e r ( a )

MMP 413 7533 1058 12560

Av. No. of Dead Bees Per Hive(b) MMP + S t i c k e r % Reduction 125 (1%)(c) 70 1916 (2%)(c) 75 360 70 5705 55

Experimental Pennwalt s t i c k e r f o r m u l a t i o n no. 1253. Over background. S t i c k e r s o l i d s c o n c e n t r a t i o n i n tank mix.

These r e s u l t s were confirmed i n l a r g e r s c a l e f i e l d t r i a l s u s i n g a e r i a l a p p l i c a t i o n s on sunflowers and a l f a l f a . Tests conducted by USDA and Texas A&M researchers near Lubbock, Texas, on blooming sunflowers (10) and by E. L. A t k i n s of the U n i v e r s i t y of C a l i f o r n i a on blooming a l f a l f a (11) gave r e d u c t i o n s i n bee m o r t a l i t y versus MMP alone of 65 and 80 to 90%, r e s p e c t i v e l y . A study by r e s e a r c h e r s at the USDA Honey Bee P e s t i c i d e - D i s e a s e s Research Laboratory, Laramie, Wyoming, (12) was conducted on sunflowers with bee c o l o n i e s placed immediately adjacent to the f i e l d s t r e a t e d with MMP and MMP S t i c k e r combinations, respect i v e l y . A 49% r e d u c t i o n i n bee m o r t a l i t y was noted i n t h i s t e s t along w i t h a 79% decrease i n methyl p a r a t h i o n r e s i d u e s i n p o l l e n brought back from the s t i c k e r - t r e a t e d f i e l d (Table V I ) .


10.

DAHL AND LOWELL


Table VI.

Crop Sunflowers (Wyoming) Sunflowers (Texas) Alfalfa (California) a. b.

Microencapsulation and Non- Target Insects

147

Comparison of Bee M o r t a l i t y Large-Scale Tests on Blooming Crops - MMP v s . MMP Plus S t i c k e r

MMP 765

Av. No. of Dead Bees Per MMP + S t i c k e r 387

13511

4682

508

100 29

Hive(a) Reduction 49 65

(l%)(b) (2%)(b)

80 94

Versus background. S t i c k e r s o l i d s cone, i n tank mix.

E f f e c t of MMP on Entomophagous Insects The e f f e c t s of MMP on entomophagous ( p a r a s i t i c and predatory) i n s e c t species have been evaluated p r i m a r i l y on a l f a l f a and apples, two crops where MMP i s considered a standard treatment. E f f e c t s on these b e n e f i c i a l i n s e c t groups have a l s o been i n v e s t i gated on corn and c o t t o n , but t o a l e s s e r extent. The a v a i l a b l e data are summarized i n Tables VII through IX. These data, i n g e n e r a l , show MMP t o have a minimal o r no d e t r i m e n t a l e f f e c t on most of the t e s t s p e c i e s . For the most p a r t , p a r a s i t i c and predatory i n s e c t populations were reduced by l e s s than 50% (Table V I I ) . In s e v e r a l i n s t a n c e s , the r e d u c t i o n approached 70% (Table V I I I ) . Even c o n s i d e r i n g the l a t t e r l e v e l of r e d u c t i o n , a l a r g e nucleus would be a v a i l a b l e from which b e n e f i c i a l i n s e c t populations could q u i c k l y r e b u i l d . As shown by the t e s t data, i n some areas the p a r a s i t i c and predatory i n s e c t populations have even increased d e s p i t e MMP a p p l i c a t i o n s (Table V I I ) . In these l o c a t i o n s phosphate r e s i s tance i s suspected. However, MMP i s e f f e c t i v e against the pest s p e c i e s , as evidenced by i t s continued use. The use of MMP a t lower r a t e s (compared to MPEC) t o reduce the pest populations below the economic i n j u r y l e v e l , w h i l e

American Chemical Society Library 1155 16th St. H. W.

In Advances in Pesticide Formulation Technology; Scher, H.; Washington, D. C. 20036 ACS Symposium Series; American Chemical Society: Washington, DC, 1984.

148


Table V I I .

Impact of MMP on Entomophagous I n s e c t s : Minimal E f f e c t (50-100% S u r v i v a l of Check Population)


Crop Species A l f a l f a Bathypleotes Spiders Apples Arriblyseius

ourculionis fallaois

Predacious bugs Lady B e e t l e s

Metaseiulus occidentalis Stethorus punotum Predacious mites (Stigmaeidae) Predacious mites

Corn Cotton

Predacious mites Lacewings P i r a t e bugs Lady B e e t l e s

(Typhlodromus) (Zetzellia)

Nabids (Predacious bugs)

Location MO, CA UT PA, NY MI*,OH* WA WA WA* PA*

MI WA WI WA,NY MO MO TX TX

Researcher Huggins,Davis Davis Hull,Lienk Howitt,Hall Covey Covey Hoyt Hull, Asquith(1975) Asquith(1976) Howitt Covey,Secondo Davis Secondo, Weizes Keaster Keaster Nemec Nemec

* P o p u l a t i o n increased over check

Table V I I I . Impact of MMP on Entomophagous I n s e c t s : S u b s t a n t i a l S u r v i v a l (30-49% of Check Population) Crop Species A l f a l f a Bathypleotes

ourculionis

Nabids (Predacious bugs) Corn Cotton

Lady B e e t l e s Bénéficiais (species unknown)

Location MO, CA UT MO MO AR

Researcher Huggins,Davis Davis Huggins Keaster Kimbrough


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s t i l l having the p a r a s i t i c and predatory i n s e c t s present to maintain the p o p u l a t i o n below t h i s t h r e s h o l d , i s a r e a l possibility. Obviously, development of Integrated Pest Management (IPM) programs i s a complicated, time-consuming process, and determining the optimum use f o r MMP w i l l take s e v e r a l seasons of t e s t i n g s on any given crop. In some areas, p a r a s i t i c and predatory i n s e c t populations appeared to be h i g h l y s u s c e p t i b l e to MMP (Table I X ) .


Table IX.

Impact of MMP on Entomophagous I n s e c t s : S u r v i v a l (< 30% of Check Population)

Species

Low

Crop Alfalfa

Location (predatory beetles)UT,NY Lady B e e t l e s M0*,UT* CA* Nabids (predacious bugs) UT,MI

Apples

Arriblyseius fallaois

NY

Researcher Davis,Gauthier Huggins,Davis Lamborn Davis, Ruppel Weires

Corn Cotton

(predacious mite) Anthooorids (predacious bugs) Aphelinus mali ( p a r a s i t i c wasp) Nabids (predacious bugs) P a r a s i t i c hymenoptera

CA CA MI TX

Pass Pass Ruppel Nemec

Cocoinellids

* Complete K i l l There i t i s q u i t e l i k e l y that no degree of r e s i s t a n c e e x i s t e d i n the n a t i v e p o p u l a t i o n . The s e l e c t i o n pressure most l i k e l y had not been as i n t e n s e , and even with the reduced r a t e of a c t i v e i n g r e d i e n t introduced by MMP (compared to MPEC), p a r a s i t i c and predatory i n s e c t r e d u c t i o n was s i g n i f i c a n t . MMP introduces l e s s a c t i v e i n g r e d i e n t than MPEC i n t o an a g r i c u l t u r a l ecosystem as a r e s u l t of the reduced r a t e s f r e quently p o s s i b l e with an encapsulated f o r m u l a t i o n . With l e s s m a t e r i a l being introduced, the e f f e c t on many p a r a s i t i c and predatory i n s e c t s i s lessened, e s p e c i a l l y i f a degree of t o l e r a n c e already e x i s t s i n t h e i r p o p u l a t i o n . I t i s hoped that with f u r t h e r research on the u s e f u l n e s s of MMP i n IPM, the i n s e c t i c i d e w i l l f u l f i l l the promise which the data discussed here suggest. Conclusions In summary, s t u d i e s conducted by Pennwalt Corporation, USDA, and u n i v e r s i t y researchers have demonstrated that microencapsulated methyl p a r a t h i o n does not represent an increased hazard to bees when compared to conventional formulations of methyl parathion; on the c o n t r a r y , i t i s found to be l e s s hazardous i n c o n t r o l l e d


A D V A N C E S IN PESTICIDE F O R M U L A T I O N T E C H N O L O G Y

150

t e s t s on c e r t a i n crops. In a d d i t i o n , s t u d i e s w i t h s p e c i a l a d d i t i v e s i n the spray tank suggest that the bee t o x i c i t y of t h i s i n s e c t i c i d e can be d r a m a t i c a l l y reduced f u r t h e r . This l a t t e r research i s c o n t i n u i n g . The reduced e f f e c t s on many p a r a s i t i c and predatory i n s e c t s suggest the c a r e f u l e v a l u a t i o n of MMP i n IPM programs. Further s t u d i e s are needed to f u l l y e x p l o i t t h i s b e n e f i c i a l r e s u l t of microencapsulation.


Literature Cited 1. Erickson, Ε. Η., personal communication. 2. Johansen, C. Α.; Kious, C. W. Glean. Bee Cult. 1978, 382-385. 3. Johansen, C. Α.; Brown, F. C. Environ. Entomol. 1972 (1) 385. 4. Morse, R. A. J. Econ. Entomol. 1961, 54, 566. 5. Erickson, Ε. H., personal communication. 6. Stoner, Α.; Wilson, W. T. J. Kansas Entomol. Soc. 1983, 56 (2) 234-240. 7. Stoner, Α.; Wilson, W. T.; Rhodes, H. A. Environ. Entomol. 1982, 11, 53-59. 8. Erickson, B. R., personal communication. 9. Moffett, J. O.; Harvey, J.; Stoner, A. The Southwestern Entomologist 1983, 8 (2), 113-117. 10. Wilson, W. T., personal communication. 11. Atkins, E. L., personal communication. 12. Ross, B.; Harvey, J. Am. Bee Journal 1981, 510-516. RECEIVED

February 9, 1984


Advances in Pesticide Formulation Technology - American Chemical

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