Controlled Release Pesticides

16 Controlled Release Formulations of Insect Growth Regulators and Pheromones—Evaluation Methods and Field Test Results J. W. YOUNG, T. M. GRAVES, and R. CURTIS

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Zoecon Corp., 975 California Ave., Palo Alto, Calif. 94304 M. M. FURNISS Forest Service, U.S. Department of Agriculture, Moscow, Idaho 83843 This third section of our Symposium has been entitled "Utility of Controlled Release Pesticides." It is my intention to share with you three instances in my experience in which controlled release techniques provided the key element of utility. In each case, the availability of a controlled delivery system made a product possible which would otherwise have been impossible. I will attempt to outline for you the formulation screening procedures which were used, and to indicate with some field data the effectiveness of the final delivery system. Mosquito Larvicide To properly introduce this first topic, I will need to describe briefly the mode of action of the active ingredient since that has an important bearing on the nature of the problem. The factors controlling insect growth and metamorphosis have been the subject of biological investigations since early in this century. By the 1960s, i t was known that particular glands secreted substances which initiated the molting process in insects, and which controlled the complex series of metamorphoses from egg, through larva and pupa, to adult (1). One hormone, secreted by a small pair of glands called the corpora allata, was known to be responsible for the maintenance of preadult characters throughout the immature life stages of insects. It is the lowering of titre of this material, called Juvenile Hormone, which allows for metamorphosis of immature insects into adults. It had been speculated that treatment of an insect with Juvenile Hormone at a time when the hormone should have been absent should cause i t to carry larval characteristics into the next developmental stage -- a derangement of the normal process which would in all likelihood be lethal. In 1967, a research group at the University of Wisconsin announced the structure of a Juvenile Hormone (JH I) (2). A closely related structure was identified soon afterward (JH II) (3). The third natural Juvenile Hormone (JH III) was discovered in our own laboratories using a novel tissue culture technique (4). 184

Scher; Controlled Release Pesticides ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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JH I

JH

II

JH

III

In 1968, Zoecon was formed with one s p e c i f i c immediate g o a l , among o t h e r s , o f developing from these d i s c o v e r i e s a new, hopeful l y s e l e c t i v e , i n s e c t c o n t r o l agent. One o f the f i r s t o f the J u v e n i l e Hormone-type m a t e r i a l s p r e pared i n Zoecon's l a b o r a t o r i e s which appeared f e a s i b l e f o r commerc i a l i z a t i o n now c a r r i e s the common name "methoprene" and our trademark "ALTOSID®."

methoprene ALTOSID® IGR Because o f t h e i r mode o f a c t i o n , methoprene and chemicals l i k e i t are now c a l l e d " I n s e c t Growth Regulators" (IGR). The e f f e c t s o f treatment with IGRs vary somewhat from one i n s e c t to another, but i n g e n e r a l , i n s e c t s e n s i t i v i t y to the compounds occurs l a t e i n l a r v a l development, with m o r t a l i t y due to morphological effects* and p h y s i o l o g i c a l imperfections delayed u n t i l the l a s t l a r v a l i n s t a r or the pupal stage. One o f the f i r s t a p p l i c a t i o n s o f methoprene which we explored, once i t s b i o l o g i c a l c h a r a c t e r i s t i c s were known, was i t s use as a mosquito l a r v i c i d e . The mode o f a c t i o n o f IGRs on mosquito larvae i s very d i f f e r e n t from c l a s s i c a l i n s e c t i c i d e s . Rather than t o x i c i t y to larvae soon a f t e r treatment, IGR-treated larvae develop normally through the pupal stage, but then f a i l to emerge as adults. This unusual s o r t o f a c t i v i t y has made necessary several new developments i n f i e l d t r i a l e v a l u a t i o n methods. It was not p o s s i b l e to simply count dead v s . l i v e larvae i n order to gauge the e f f e c t o f the treatment. In some c a s e s , t r e a t e d water c o n t a i n i n g larvae was sampled i n the f i e l d , brought i n t o the l a b o r a t o r y , and the larvae observed f o r i n h i b i t i o n o f a d u l t emergence. In other t r i a l s , larvae were introduced i n t o t r e a t e d water e i t h e r i n the l a b o r a t o r y or i n s p e c i a l l y designed f l o a t i n g cages.


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CONTROLLED RELEASE

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Soon a f t e r we began f i e l d t e s t i n g o f methoprene, we noted r a p i d degradation — the inverse o f the problem encountered with sometimes t o o - p e r s i s t e n t conventional p e s t i c i d e s . The a c t i v e i n gredient was simply not l a s t i n g long enough under f i e l d exposure c o n d i t i o n s to be b i o l o g i c a l l y e f f e c t i v e . Chemical a n a l y s i s q u i c k l y confirmed that at l e a s t two d i f f e r e n t r e a c t i o n s were occuring which converted methoprene to i n a c t i v e m a t e r i a l s ( 5 j . The f i r s t o f these processes was found to be r a p i d u l t r a v i o l e t l i g h t - i n duced i s o m e r i z a t i o n to the much l e s s a c t i v e 2Z,4E isomer (B below).


hv

I

A

^

Table I shows that a second p r o c e s s , i n v o l v i n g decomposition to nonisomenc products, occurs simultaneously. Table I Percent Methoprene Isomers Remaining A f t e r Exposure to S u n l i g h t %Β 10 30 39 36 27

Initial 1 hour 2 hours 4 hours 8 hours

%A

% A+B 100 95 89 78 62

90 65 50 42 35

It has s i n c e been determined (5} that s u n l i g h t i n i t i a t e s r a p i d de cay to the b i o l o g i c a l l y i n a c t i v e decomposition products shown below.

A

7

+

In these chemical experiments, the h a l f - l i f e of methoprene i n sun l i g h t was l e s s than one day as an aqueous emulsion and about four hours as a t h i n f i l m on g l a s s . The r a p i d decomposition i n d i c a t e d i n Table I merely served as chemical confirmation of the complete f a i l u r e of conventional f o r mulations of methoprene i n e a r l y f i e l d t e s t s , although the same formulations had been h i g h l y e f f e c t i v e i n l a b o r a t o r y t e s t s . Even though we were d e a l i n g with floodwater mosquitoes and synchronous p o p u l a t i o n s , the s u s c e p t i b i l i t y of fourth i n s t a r larvae to metho prene required p i n p o i n t a p p l i c a t i o n timing f o r e f f e c t i v e n e s s .


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A formulation was thus needed which protected the a c t i v e i n gredient and released i t i n b i o l o g i c a l l y a c t i v e form, but d i d not leave residues beyond those required f o r e f f e c t i v e n e s s (see Table II). Table

II


P r o j e c t Goals — ALTOSID Mosquito Formulation 1. 2. 3. 4.

Decrease r a t e of i s o m e r i z a t i o n to the l e s s a c t i v e isomer. Decrease r a t e o f o x i d a t i v e degradation. Achieve e f f i c i e n t use o f a c t i v e i n g r e d i e n t — must be b i o l o g i c a l l y e f f e c t i v e f o r 4-10 days. Predictable residues.

In preparing candidate f o r m u l a t i o n s , the p r i n c i p a l v a r i a b l e s which we explored are those shown i n Table I I I . Formulations were f i r s t screened i n l a b o r a t o r y glassware. Aqueous d i l u t i o n s were subjected to aging under a r t i f i c i a l l i g h t , and then i n f e s t e d with s e n s i t i v e fourth i n s t a r l a r v a e (6). L a t e r t e s t s were conducted s i m i l a r l y , but i n s e r i e s of outdoor ponds e i t h e r one meter or 130 meters i n s i z e (7_). B i o l o g i c a l t e s t i n g revealed most s i g n i f i c a n t gains i n e f f e c t i v e l i f e t i m e o f the a c t i v e i n g r e d i e n t with a p o l y amide formulation which we now c a l l ALTOSID SR-10. The product i s an aqueous d i s p e r s i o n o f m i c r o p a r t i c l e s i n the 1-10 micron range, and contains 10% a c t i v e i n g r e d i e n t . Our formulation procedure does not y i e l d true microcapsules — o i l d r o p l e t s surrounded by a f i l m o f polymeric wall m a t e r i a l . ALTOSID SR-10 appears on m i c r o scopic examination to be a matrix which i s s p o n g e - l i k e i n c r o s s section. 2

2

Table Formulation

III Variables

1.

Capsule wall/matrix

2. 3. 4. 5.

Ratio o f polymer to a c t i v e Degree o f c r o s s - l i n k i n g Particle size P a r t i c l e specific gravity

material ingredient

The e f f e c t o f t h i s formulation on the rate o f i s o m e r i z a t i o n to the 2Z,4E isomer (B, Table I ) , i s shown i n Figure 1. Although t h a t process i s not stopped a l t o g e t h e r , i t s rate i s s u b s t a n t i a l l y decreased r e l a t i v e to that o f unprotected material s u p p l i e d as an e m u l s i f i a b l e concentrate ( E . C . ) f o r m u l a t i o n . Methoprene has a water s o l u b i l i t y of 1.4 parts per m i l l i o n (ppm). Its threshold of b i o l o g i c a l a c t i v i t y and the l e v e l o f d e t e c t i o n by our residue methods are both about 1 part per b i l l i o n (ppb). Figure 2 shows the cumulative e f f e c t on the p r o d u c t ' s l i f e t i m e o f the decrease



188

C O N T R O L L E D R E L E A S E PESTICIDES

both i n i s o m e r i z a t i o n rate and i n r a t e o f o x i d a t i v e degradation. Many o f our e a r l y formulation screening experiments i n v o l v e d twofold e v a l u a t i o n procedures. Water was sampled and analyzed chemically for residues o f methoprene a f t e r various aging p e r i o d s . At the same time, b i o l o g i c a l performance was monitored by p l a c i n g s e n s i t i v e fourth i n s t a r mosquito larvae i n the t r e a t e d water. We repeatedly saw instances o f complete b i o l o g i c a l e f f e c t i v e n e s s of the treatment while no methoprene was c h e m i c a l l y d e t e c t a b l e . It was not u n t i l we began to note the time o f day at which samples were taken f o r chemical a n a l y s i s that a pattern emerged. That pattern i s shown i n Figure 3. Our r a t i o n a l i z a t i o n o f t h i s r e s u l t i s that the rate o f decomposition o f released methoprene exceeds the r e l e a s e rate i t s e l f during the s u n l i t hours o f the day. Dur ing the c o o l , dark hours, r e l e a s e o f the a c t i v e i n g r e d i e n t c o n tinues and e s t a b l i s h e s a b i o l o g i c a l l y e f f i c a c i o u s pool of metho prene. A n a l y t i c a l Methods. E v a l u a t i o n o f the e f f i c i e n c y o f various mi c r o e n c a p s u l a t i on procedures i s a problem which has p e r s i s t e d throughout t h i s and a l l s i m i l a r p r o j e c t s with which we have been involved. It occurs i n the i n i t i a l stages of product development when one needs a r a p i d means o f e v a l u a t i n g the e f f e c t o f formu l a t i o n v a r i a b l e s , and p e r s i s t s throughout the l i f e t i m e of the product as a vitaΤ aspect o f q u a l i t y c o n t r o l . The problem, simply s t a t e d , i s not too d i f f e r e n t from one encountered by high energy p h y s i c i s t s — i n measuring t h i s p a r t i c u l a r property o f the p a r t i c l e , one cannot avoid changing the nature o f the p a r t i c l e i t s e l f . We have a r r i v e d at a method which, although i t undoubtedly does s u f f e r from t h i s d e f e c t , serves the purpose of y i e l d i n g h i g h l y r e p r o d u c i b l e data i n a r e l a t i v e l y r a p i d f a s h i o n . The method i t s e l f i s summarized i n Table IV, while the r e s u l t s o f two r e p r e s e n t a t i v e analyses are shown i n Figure 4. At short time i n t e r v a l s , the curve obtained i s very n o n l i n e a r , which i s undoubtedly due to d i s s o l u t i o n o f unencapsulated material along with a q u a n t i t y at or near the surface o f the p a r t i c l e s . At longer i n t e r v a l s , however, we f i n d that with the proper choice o f e x t r a c t i n g s o l v e n t , very r e p r o d u c i b l e s t r a i g h t l i n e s are obtained which allow the character i z a t i o n o f the p a r t i c u l a r batch o f product. For s i m p l i c i t y , the term " e n c a p s u l a t i o n e f f i c i e n c y " i s em ployed here. The method as o u t l i n e d appears to have v a l i d i t y i n a wide range o f formulations — true encapsulates as well as ma t r i x systems such as ALTOSID SR-10.


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and Pheromones

70/30


ALTOSID SR-10 ALTOSID E . C . 0.1 ppm i n water

Figure 1.

Change of methoprene isomer ratio—sunlight

ι 1

ι 2

ι 3

ι 4

•

5

• 6

• 7

8

•

9

days Figure 2.

Methoprene

decomposition—sunlight


1

10


Figure 3. Effect of sampling time on methoprene residues detected


en

1

W

>

w

a

(Η

ο

ο

ο

ο

Formulions

YOUNG E T A L .

100


β

Pheromones

r

-A-

80 methoprene encap sulated

of Insect Regulators and

« Run #25 84% encapsulated

40

20

15

100

30 60 90 E x t r a c t i o n time, minutes

ι—

80

Run #26 22% encapsulated

methoprene encap60 sulated 40

20

15

30 60 90 E x t r a c t i o n t i m e , minutes

Figure 4. Encapsulation efficiency


192


Table Analytical Step 1:


Step 2:

Step 3:

Method - -

IV

Encapsulation E f f i c i e n c y

Analyze t o t a l A . I . a v a i l a b l e . High shear mixing to rupture p a r t i c l e s — strong solvent system. M i l d e x t r a c t i o n procedure A) D i l u t e c o n t r o l l e d r e l e a s e formulation i n water. B) Add s o l v e n t c o n t a i n i n g i n t e r n a l standard f o r GLC a n a l y s i s . Solvent chosen i s solvent f o r a c t i v e i n g r e d i e n t , nonsolvent f o r polymer, immiscible i n water. C) Shake the sample c o n t a i n i n g the solvent on a wrist-shaker. Remove a l i q u o t s o f the supernatant s o l v e n t f o r a n a l y s i s at standard i n t e r vals. D) Analyze (by GLC or other s u i t a b l e means) f o r % a c t i v e i n g r e d i e n t i n the s o l v e n t . Determine % encapsulated A . I . A) P l o t X v s . e x t r a c t i o n time. X = 100 B)

wt. detected [total wt. a v a i l a b l e

E x t r a p o l a t e to zero time.

F l y Control — P o u l t r y Feed Through Another area i n v e s t i g a t e d very a c t i v e l y with methoprene i s that o f f l y c o n t r o l i n p o u l t r y houses. In caged l a y i n g hen opera t i o n s i n p a r t i c u l a r , f l i e s present serious nuisance and disease vector problems. Managers o f these operations are forced to follow very r i g i d programs o f manure c l e a n - o u t and frequent i n s e c t i c i d e sprays to c o n t r o l t h e i r f l y p o p u l a t i o n s . Because o f the e x t r a o r d i n a r y safety o f ALTOSID, we f e l t i t could be incorporated i n t o the feed r a t i o n s o f the b i r d s . I f i t emerged i n t a c t i n the manure, and any f l y larvae developing there would not emerge as adults. In p r e l i m i n a r y t e s t s , small groups o f l a y i n g hens were fed with a r a t i o n t r e a t e d with t e c h n i c a l methoprene over a wide range o f c o n c e n t r a t i o n s . The manure was i n f e s t e d with housefly l a r v a e , and the various treatments were scored f o r percent i n h i b i t i o n o f a d u l t emergence. The r e s u l t s are shown i n Table V. In t h i s and i n subsequent work, the l e v e l o f methoprene i n t h e manure required f o r e f f e c t i v e c o n t r o l f e l l i n the range of 1-2 ppm.


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Table V Rate o f Methoprene i n P o u l t r y Feed, ppm 10 25 50 75 100 125 200 400

Percent I n h i b i t i o n o f A d u l t House F l y Emergence 68 81 96 98 99+ 100 100 100

Level o f Methoprene Detected i n Manure, EË1 1.0 1.5 2.5

Economic a n a l y s i s i n d i c a t e d to us that the market would bear the c o s t o f the product only i f the l e v e l o f methoprene to be i n corporated i n t o the feed could be reduced to 10 ppm or l e s s and that >95% f l y c o n t r o l was r e q u i r e d . These f a c t o r s , t h e n , defined the t a r g e t f o r formulation work. When fed as t e c h n i c a l m a t e r i a l , the amount o f methoprene excreted i n t a c t was on the order o f 3%. I t was our task to formulate the product to y i e l d a f i v e - to t e n f o l d increase i n feed-through e f f i c i e n c y . Formulation screening involved both chemical and b i o l o g i c a l e v a l u a t i o n o f each candidate. Not only was i t necessary to d e t e r mine the l e v e l o f a c t i v e i n g r e d i e n t present i n the p o u l t r y manure, but i t s b i o a v a i l a b i l i t y had to be a s c e r t a i n e d . Small groups o f hens were fed r a t i o n s c o n t a i n i n g 10 ppm methoprene i n a v a r i e t y o f f o r m u l a t i o n s , and manure was sampled 10 and 14 days a f t e r t r e a t ment. Part o f the sample was i n o c c u l a t e d with house f l y l a r v a e , and methoprene residues determined by chemical a n a l y s i s were compared with the percent i n h i b i t i o n o f a d u l t f l y emergence. Figure 5 shows the r e s u l t s f o r several formulations t e s t e d e a r l y i n the program (numbers 1 through 7) and for the formulation ALTOSID PS-10 which u l t i m a t e l y emerged as s u i t a b l e f o r f u r t h e r t e s t i n g (number8). It should be noted t h a t the b i o l o g i c a l data i n d i c a t e s c o n s i d e r a b l y greater e f f i c a c y than would be expected at these residue l e v e l s . This probably r e f l e c t s the somewhat i d e a l i z e d c o n d i t i o n s o f the l a b o r a t o r y experiment. The e x c e l l e n t performance o f ALTOSID PS-10 i n s m a l l - s c a l e e f f i c a c y experiments prompted us to f i l e f o r an experimental permit r e g i s t r a t i o n to allow expanded t e s t i n g . Under the experimental permit, t e s t i n g involved extremely l a r g e numbers of b i r d s i n several s t a t e s . The r e s u l t s o f two o f the many t r i a l s conducted under the experimental permit are shown at the bottom o f Table VI. While i n 1974, the treatment y i e l d e d 90% or g r e a t e r c o n t r o l i n most i n s t a n c e s , e f f e c t i v e n e s s i n f u l l - h o u s e t r i a l s a year l a t e r was v a r i able and much lower.


Scher; Controlled Release Pesticides ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 0.55

Celite

Celite/Polyurea

ALTOSID

6

7

8

Figure 5.

PS-10

100

98

96

98

97

84

93

25

% Control Avg. of 3 Reps

Formuhtion screening: poultry feed-through—10

2.00

0.39

0.62

Calcium S i l i c a t e / Polyamide Coating

5

Coating

0.21

Calcium

4

Silicate

0.22

Fumed S i l i c a

3

0.36

Technical

Residue (ppm)

2

Control

Type

Untreated

Formulation

1

Sample #

ppm in feed

2.50

0.32

0.62

0.94

0.26

0.29

100

92

98

97

71

71

92

12

0.39

% Control Avg. of 3 Reps

Residue (ppm)


n

CO

w

13

m >

s

α

Ο

8

ç£5

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Table VI


ALTOSID PS-10 Manure Residue & E f f i c a c y

Date 1974 1974 1974 1974 1974 1975 1975

Test Location California California California Texas Texas California Texas

Feeding Rate 10 ppm 10 ppm 10 ppm 10 ppm 10 ppm 10 ppm 10 ppm

Formulation PS-10 PS-10 PS-10 PS-10 PS-10 PS-10 PS-10

Percent Control 97 95 98 90 89 42 39

ppm i n Manure 1.2 1.6 2.0 1.4 1.6 1.7 1.5

The c o n t r a s t i n g r e s u l t s are undoubtedly r e l a t e d to the d i f ference i n e v a l u a t i o n techniques employed. In small t r i a l s , i t was necessary to judge the e f f e c t i v e n e s s o f the treatment by monit o r i n g i n h i b i t i o n o f a d u l t f l y emergence from small closed c o n t a i n e r s o f manure. In l a r g e r t e s t s , movement o f the natural popu l a t i o n of f l y larvae was not r e s t r i c t e d , and e v a l u a t i o n was made by actual f l y counts on a whole ranch or whole house b a s i s . The f a i l u r e o f l a r g e t e s t s to demonstrate the commercial v i a b i l i t y o f t h i s product r e s u l t s from f a i l u r e o f the IGR to act during e a r l y stages o f l a r v a l development. It was observed that f l y larvae developing i n wet areas i n the manure tend to move s h o r t l y before pupation to d r i e d areas — away from f r e s h l y deposited droppings. Since t h i s time i n the l i f e c y c l e o f the f l y c o i n c i d e s with the period o f s e n s i t i v i t y to the IGR, the time o f exposure to the a c t i v e i n g r e d i e n t i s i n s u f f i c i e n t . In many c a s e s , t h i s phenomenon was aggravated i n 1975 by an unusually r a i n y f l y season. Although these r e s u l t s were d i s a p p o i n t i n g , they serve to i l l u s t r a t e an important p o i n t . No matter how well one b e l i e v e s to have designed s m a l l - s c a l e experiments, the jump to commercial s i z e d t e s t i n g i n v a r i a b l y brings i n t o play a number o f v a r i a b l e s not present i n the smaller t r i a l s . Anti-Aggregative

Pheromone — Douglas F i r Bark Beetle

The Douglas F i r Bark Beetle i n f e s t s Douglas f i r f o r e s t s throughout much o f the Northwestern United S t a t e s . Its population o c c a s i o n a l l y reaches epidemic p r o p o r t i o n s , e s p e c i a l l y i n trees weakened by windthrow or d i s e a s e . It was discovered i n 1971 (8) that the f r a s s o f the female beetle contains a pheromone, 3-methyl-2-cyclohexen-1-one (MCH), which was l a t e r shown (9,10) to have a n t i - a g g r e g a t i v e e f f e c t s on a d u l t b e e t l e s . In 1974, F u r n i s s e t al (11) reported on f i e l d t r i a l s with f e l l e d host trees which showed t h a t , when released o p t i m a l l y , the pheromone served to r e duce beetle attacks upon s u s c e p t i b l e trees by 96%. The pheromone was dispensed i n t h i s experiment as neat material from small metal


196

CONTROLLED RELEASE

PESTICIDES

c a n i s t e r s mounted at even spacings around the t r e e on wooden stakes. T h i s t r i a l served to demonstrate the e f f e c t i v e n e s s o f the treatment, and r e f i n e d the optimum r a t e o f pheromone r e l e a s e to a narrow range. Q


3-methyl-2-cyclohexen-1-ι We became involved a t veloping a formulation f o r v o l a t i l e and water s o l u b l e l a t i o n would i d e a l l y match

t h i s stage, and began work aimed a t de season-long release o f MCH, a h i g h l y material. The p r o p e r t i e s of the formu those o u t l i n e d i n Table VII. Table

VII

Goals - - MCH Formulation 1. 2. 3.

Project

Release MCH at r a t e o f 0 . 1 - 1 . 3 grams/acre/day E f f e c t i v e f o r 30-60 days S u i t a b l e f o r a p p l i c a t i o n by a i r - - must penetrate f o r e s t canopy Biodegradable Nontoxic Low c o s t

4. 5. 6.

The f i r s t step i n our program was the development o f a r e lease rate method s u i t a b l e f o r l a b o r a t o r y screening of the many formulations which would be necessary (12). The method as i t de veloped involved the use of t r i t i u m - l a b e l e d MCH. The formulation to be tested was placed i n a modified f l a s k (13) f i t t e d with i n l e t and o u t l e t f o r c a r r i e r gas flow. To the o u t l e t o f the f l a s k was attached a small g l a s s tube packed with 0.25 grams o f Porapak® QS (50-80 mesh) (14). Dry nitrogen c a r r i e r gas was passed through the f l a s k and trapping column for one hour at a rate of 175 ml/ minute. The trapping column was then removed, and the H-MCH r e leased from the formulation was e l u t e d i n t o a s c i n t i l l a t i o n v i a l with 10 c c * s o f hexane.. S c i n t i l l a t i o n f l u i d was added to the v i a l , and the H-MCH content was determined d i r e c t l y by s c i n t i l l a t i o n counting. Formulations were aged at ambient temperature and r e l a t i v e humidity f o r up to 60 days on p a p e r - l i n e d s t e e l t r a y s stacked i n a forced d r a f t fume hood with a constant a i r flow through the stack of t r a y s of 150 c u . f t . / m i n . Formulations were sampled f o r r e lease rate determination at the beginning of the aging period and weekly t h e r e a f t e r u n t i l the rate o f release o f H-MCH f e l l below 0.5 micrograms/hour. 3

3

3


16.

YOUNG E T A L .

Formulations

of Insect Regufators and Pheromones

Treatment

Method


Coated Molecular Sieve

1

Ρ

Granules

197

Douglas F i r Beetle Brood Attacks 3

0.1**

ι**

L i q u i d Standard

Ρ

0.2**

4**

Polyamide Granules A

Β

0.3*

33 NS

Polyamide Granules Β

Β

0.4*

Polyamide Granules C

Β

0.6*

26 NS

Β

1.7 NS

51 NS

Β

3.5 NS

42 NS

Control

-

4.8

45

Coated Kobrite Granules

Β

4.9 NS

54 NS


Granules


Granules

P_ = i n cans on stakes 4 f t .

1

B_ = broadcast

2

2

above ground, 10 by 10 f t . spacing

by hand.

A p p l i e d at a rate of 1/10 that of the other

granules.

d i f f e r e n c e from c o n t r o l i s s i g n i f i c a n t at the 0.01 0.5 l e v e l (*), or not s i g n i f i c a n t (NS). Figure 6.

7**

(**),

Density (no/ft ) of Douglas Fir beetle attacks and brood by treatment 2


198


T h i s formulation screening method was convenient and r a p i d enough to allow t e s t i n g o f r e l a t i v e l y l a r g e numbers o f formulation systems. We conducted r e l e a s e rate t e s t s with about 70 d i f f e r e n t formulations (several o f them r e p l i c a t e d three t i m e s ) . Release rates were run at an average o f f i v e aging i n t e r v a l s f o r each formulation. Most systems were e l i m i n a t e d from f u r t h e r c o n s i d e r a t i o n a f t e r the f i r s t few weeks of s c r e e n i n g , when the rate o f r e l e a s e o f MCH f e l l below 0.5 micrograms/hour. Twelve f o r m u l a t i o n s , however, showed promise and maintained a rate o f r e l e a s e o f H-MCH c l o s e to or above 1 microgram/hour f o r 30-60 days. These formul a t i o n s were evaluated by an independent l a b o r a t o r y (13), and e v e n t u a l l y f i v e formulations were s e l e c t e d f o r f i e l d t e s t i n g . The d e t a i l s o f t h i s f i e l d t e s t w i l l be reported s e p a r a t e l y (12). In g e n e r a l , the procedure involved treatment of i s o l a t e d , f e l l e d , host trees with the formulations at a rate o f 38 grams MCH per a c r e . The stake-mounted cans c o n t a i n i n g unformulated MCH served as a standard. Each treatment was r e p l i c a t e d three times, and s i x untreated c o n t r o l p l o t s were reserved. Treatment was made p r i o r to the f i r s t beetle f l i g h t i n A p r i l , and f i n a l e v a l u a t i o n of treatments was made i n mid-August. The r e s u l t s o f the t e s t are shown i n Figure 6. As i n d i c a t e d i n Figure 6, one o f the formulations a p p l i e d to the ground by broadcast method gave e x c e l l e n t r e s u l t s — i n d i s t i n g u i s h a b l e from the standard treatment. T h i s m a t e r i a l , a dimer a c i d polyamide granular formulation (3-8 mesh), was judged s u f f i c i e n t l y e f f e c t i v e to be used i n l a r g e - s c a l e t r i a l s i n areas o f natural windthrow. These t r i a l s are s t i l l i n the planning stage.


3

One other f o r m u l a t i o n , 13X molecular sieve granules coated with a wax/polymer system, gave e x c e l l e n t performance when p r o t e c t e d i n metal cans on stakes above the ground, but f a i l e d e n t i r e l y when broadcast on the ground. It i s l i k e l y that exposure to the high r a i n f a l l of the area and constant contact with the moist f o r e s t f l o o r e x t r a c t e d the pheromone from that f o r m u l a t i o n . Acknowledgements The authors thank Robert Lowe and Loren Dunham f o r advice and a s s i s t a n c e i n the A n a l y t i c a l Chemistry aspects o f t h i s work. Edward Wenik developed the assay method f o r encapsulation e f f i c i e n c y , and Kenneth Horwege provided valuable t e c h n i c a l a s s i s t a n c e on a l l o f the p r o j e c t s d i s c u s s e d . The MCH formulation work was funded by the U . S . D . A . , Forest S e r v i c e Contract Number 12-11-205-09.

Literature Cited 1. Wigglesworth, V.B., "The Principles of Insect Physiology," Sixth Edition, E.P. Dutton & Co., New York, 1965. 2.

Röller, H., Dahm, K.N., Sweeley, C.C., and Trost, B.M., Angew. Chem. Internat. Ed., (1967), 6, 179.


16.

YOUNG

3.

Meyer, A.S., Schneiderman, H.A., Hanzmann, Ε., Proc. Nat. Acad. Sci. USA, (1968), 60, 853.

ET AL.

Formulations


and Pheromones

199


4. Judy, K.J., Schooley, D.A., Dunham, L.L., Hall, M.S., Bergot, B.J., and Siddall, J.B., Proc. Nat. Acad. Sci. USA, (1973), 70, 1509. 5.

Quistad, G.B., Staiger, L.E., and Schooley, D.A., J. Agr. Food Chem., (1975), 23, 299.

6.

Schaefer, C.H., and Wilder, W.H., J. Econ. Ent., (1972), 65, 1066.

7.

Schaefer, C.H., and Wilder, W.H., J . Econ. Ent., (1973), 66, 913.

8.

Kinzer, G.W., Fentiman, A.F. Jr., Foltz, R.L., Rudinsky, J.A., J. Econ. Ent., (1971), 64, 970.

9.

Rudinsky, J.A., Furniss, M.M., Kline, L.N., and Schmitz, R.F., Can. Entomol., (1972), 104, 815.

10. Furniss, M.M., Kline L.N., Schmitz, R.F., and Rudinsky, J.A., Ann. Entomol. Soc. Amer., (1972), 65, 1227. 11. Furniss, M.M., Daterman, G.E., Kline, L.N., McGregor, M.D., Trostle, G.C., Pettinger, L.F., and Kudinsky, J.A., Can. Entomol., (1974), 106, 381. 12. Furniss, M.M., Young, J.W., McGregor, M.D., Livingston, R.L, and Hamel, D.R., Can. Entomol., (1977), in press. 13. Look, M., Chem. Ecol., (1976), 2, 481. 14. The use of Porapak QS was suggested (private communication) by Dr. James Trudell, Stanford University. See also Byrne, K.J., Gore, W.E., Pearce, G.T., and Silverstein, R.M., J. Chem. Ecol., (1975), 1, 1.


Controlled Release Pesticides

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