Enhanced Carbamothioate Herbicide Degradation - ACS Symposium

Chapter 3

Enhanced Carbamothioate Herbicide Degradation Research in Nebraska 1

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3

Fred W. Roeth , Robert G. Wilson , Alex R. Martin , and Patrick J. Shea 1

Department of Agronomy, University of Nebraska, Clay Center, NE 68933-0066 Department of Agronomy, University of Nebraska, Scottsbluff, NE, 69631-0224 Department of Agronomy, University of Nebraska, Lincoln, NE 68583-0915

Downloaded by TUFTS UNIV on June 3, 2018 | https://pubs.acs.org Publication Date: May 3, 1990 | doi: 10.1021/bk-1990-0426.ch003

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The half-life of EPTC was reduced about 50% by enhanced degradation which occurred on EPTC reapplication. Enhanced carbamothioate herbicide degradation was associated with unsatisfactory shattercane control in about 60% of the fields receiving a repeat treatment of EPTC or butylate. Though dietholate extender effectively prevented enhanced EPTC degradation, dietholate was ineffective on reapplication. SC-0058 extender was effective in slowing EPTC degradation in soils previously treated with EPTC, EPTC + dietholate, and EPTC + SC-0058. Dietholate and SC-0058 did not increase EPTC persistence in soil without prior EPTC treatment. Reversion of EPTC degradation from an enhanced rate to a normal rate took about 18 and 30 months in western and south central Nebraska, respectively, after two annual EPTC applications. Among the common carbamothioate herbicides, EPTC, vernolate, and butylate caused enhanced degradation and exhibited cross-adaptation; however, butylate was only partially susceptible to EPTC-enhanced degradation. Cycloate did not cause enhanced degradation nor show any susceptibility to EPTC-enhanced degradation. Use o f EPTC ( S - e t h y l d i p r o p y l c a r b a m o t h i o a t e ) h e r b i c i d e f o r weed c o n t r o l i n c o r n ( Z e a mays L.) i n c r e a s e d markedly i n t h e mid-1970's f o l l o w i n g the i n t r o d u c t i o n o f d i c h l o r m i d (2,2-dichloro-N,N-di-2propenylacetamide) safener. EPTC was p a r t i c u l a r l y e f f e c t i v e f o r c o n t r o l l i n g s h a t t e r c a n e (Sorghum b i c o l o r ( L . ) Moench), a v e r y t r o u b l e s o m e weed i n c o n t i n u o u s c o r n . A s u g a r b e e t ( B e t a v u l g a r i s L.) - f i e l d b e a n ( P h a s e o l u s v u l g a r i s L.) - c o r n r o t a t i o n i s common i n p o r t i o n s o f w e s t e r n Nebraska, and EPTC i s used f o r weed c o n t r o l i n a l l three crops. As a r e s u l t , EPTC was a p p l i e d a n n u a l l y i n many fields. 0097-6156/90/0426-0023$06.00/0 © 1990 American Chemical Society

Racke and Coats; Enhanced Biodegradation of Pesticides in the Environment ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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ENHANCED BIODEGRADATION OF PESTICIDES IN T H E ENVIRONMENT


Grower c o m p l a i n t s o f poor s h a t t e r c a n e c o n t r o l w i t h EPTC became numerous by 1977. Loss o f e f f i c a c y was i n i t i a l l y a t t r i b u t e d t o m i s a p p l i c a t i o n , i n a d e q u a t e i n c o r p o r a t i o n , and a d v e r s e e n v i r o n m e n t a l conditions. However, t h e c o n t i n u i n g w i d e s p r e a d r e p o r t s o f u n s a t i s f a c t o r y c o n t r o l w i t h EPTC s u g g e s t e d o t h e r unknown f a c t o r s must be i n v o l v e d . F i e l d and greenhouse s t u d i e s were i n i t i a t e d i n 1978 t o i d e n t i f y t h e r e a s o n s f o r poor f i e l d performance ( 1 - 3 ) . Interestingly the problem appeared t o be a s s o c i a t e d w i t h r e p e a t e d a n n u a l application. Though t h e e x t e n t o f EPTC f a i l u r e was unknown a t t h e time, a 1983-84 s u r v e y r e v e a l e d t h a t 60% and 45% o f c o r n growers i n s o u t h c e n t r a l Nebraska who used b u t y l a t e [ S - e t h y l b i s ( 2 m e t h y l p r o p y l ) c a r b a m o t h i o a t e ] o r EPTC were d i s s a t i s f i e d w i t h t h e i r weed c o n t r o l ( 4 ) . T h i s was p r o b a b l y r e p r e s e n t a t i v e o f t h e s i t u a t i o n i n 1978. One h y p o t h e s i s f o r d e c r e a s e d c o n t r o l was t h a t s h a t t e r c a n e had d e v e l o p e d r e s i s t a n c e t o EPTC. S h a t t e r c a n e seeds were c o l l e c t e d from s o i l s where EPTC had f a i l e d i n 1977 as w e l l as f i e l d s where c o n t r o l had been s a t i s f a c t o r y . I n greenhouse s t u d i e s , t h e s e s h a t t e r c a n e s o u r c e s d i d n o t d i f f e r i n EPTC r e s p o n s e from each o t h e r n o r from a s t a n d a r d f o r a g e sorghum (Sorghum b i c o l o r ( L . ) Moench) (.1,3). Thus, h e r b i c i d e r e s i s t a n c e d i d n o t e x p l a i n d i m i n i s h e d EPTC p e r f o r m a n c e . A d d i t i o n a l greenhouse s t u d i e s r e v e a l e d t h a t as s h a t t e r c a n e seed p o p u l a t i o n d e n s i t y i n c r e a s e d i n t h e s o i l , t h e number o f p l a n t s e s c a p i n g c o n t r o l i n c r e a s e d p r o p o r t i o n a t e l y (1)• While a l a r g e s h a t t e r c a n e s o i l seedbank c o u l d c o n t r i b u t e t o reduced c o n t r o l , t h i s f a c t o r d i d n o t seem r e s p o n s i b l e f o r t o t a l f a i l u r e . The e f f e c t of c o r n s t o v e r on EPTC performance was e v a l u a t e d i n the greenhouse ( 3 ) . A t 1 ppm EPTC, b i o a c t i v i t y was r e d u c e d a t s t o v e r l e v e l s o f 3 and 6 g p e r 500 g o f s o i l . The i n f l u e n c e o f t h e s t o v e r c o u l d be overcome by i n c r e a s i n g t h e a p p l i c a t i o n r a t e t o 2 ppm. F i e l d s t u d i e s i n v o l v i n g r e s i d u e removal p r i o r t o EPTC a p p l i c a t i o n showed m i n i m a l d i f f e r e n c e s a t normal EPTC r a t e s (2^). S h a t t e r c a n e c o n t r o l (2) was e v a l u a t e d i n 1979 i n f i e l d s w i t h p r e v i o u s EPTC use ( S a r o n v i l l e ) and w i t h o u t p r e v i o u s EPTC use (Douglas). A t S a r o n v i l l e t h e t r e a t m e n t s o f EPTC + d i c h l o r m i d r e d u c e d s h a t t e r c a n e head p r o d u c t i o n o n l y 35% compared t o t h e u n t r e a t e d c o n t r o l ( T a b l e I ) . A t Douglas, EPTC p r o v i d e d 90 t o 95% s h a t t e r c a n e control. The i n c l u s i o n o f an e x p e r i m e n t a l e x t e n d e r , d i e t h o l a t e (0,0d i e t h y l 0 - p h e n y l p h o s p h o r o t h i o a t e ) , w i t h EPTC improved c o n t r o l a t S a r o n v i l l e but n o t a t Douglas. An e x t e n d e r i s a c h e m i c a l a d d i t i v e which can p r o l o n g t h e p e r s i s t e n c e o f a p e s t i c i d e . Follow-up greenhouse work showed t h a t t h e e x t e n d e r d i d n o t i n c r e a s e EPTC a c t i v i t y but d i d r e t a r d EPTC d e g r a d a t i o n i n s o i l t r e a t e d p r e v i o u s l y w i t h EPTC ( 5 - 6 ) . L a b o r a t o r y and f i e l d e x p e r i m e n t s conducted i n 1980 ( 5 , 7-9) demonstrated enhanced d e g r a d a t i o n o f EPTC i n s o i l s w i t h p r e v i o u s EPTC use w h i l e d i e t h o l a t e e f f e c t i v e l y c o u n t e r a c t e d t h i s e f f e c t . The cause of r a p i d d e g r a d a t i o n was d e t e r m i n e d t o be m i c r o b i o l o g i c a l . Enhanced EPTC d e g r a d a t i o n had n o t been p r e v i o u s l y o b s e r v e d i n our r e s e a r c h because h e r b i c i d e e v a l u a t i o n s were n o t conducted on t h e same s i t e i n consecutive years. S e v e r a l a u t h o r s ( H ) , 1^1) have r e v i e w e d t h e h i s t o r y o f enhanced h e r b i c i d e d e g r a d a t i o n i n d e t a i l so t h i s paper c o n c e n t r a t e s on r e s e a r c h conducted i n Nebraska. Concurrent research i n o t h e r s t a t e s and c o u n t r i e s c o n t r i b u t e d e s s e n t i a l l y t o p r o g r e s s i n u n d e r s t a n d i n g t h i s phenomenon and a p p r e c i a t i n g i t s impact.


3. ROETH ET AL.

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Carbamothioate Herbicide Degradation

T a b l e I . S h a t t e r c a n e c o n t r o l i n c o r n a t S a r o n v i l l e , NE, i n 1979. A l l h e r b i c i d e s were a p p l i e d p r e p l a n t and i n c o r p o r a t e d i m m e d i a t e l y !


Herbicide

Untreated Handweed + EPTC EPTC EPTC EPTC + c y a n a z i n e EPTC^ EPTC7 EPTC + cyanazine LSD

Stgms/ m

lb/A

3

A.O 4.0 6.0 A.O + 2.,0 A.O 6.0 A.O + 2..0

Heads/ m

Corn Bu/A

12A 32 8A 15A 9A 26 18 3

55 7 36 36 35 5 3 1

6 73 18 20 22 A3 A2 66

83

A

23

(.05)

* A l l EPTC was f o r m u l a t e d w i t h d i c h l o r m i d . Formulated

with d i e t h o l a t e extender

(6:1).

t Reprinted with permission from ref. 6. Copyright 1982 Weed Science.

C o n f i r m a t i o n o f Enhanced D e g r a d a t i o n . O b r i g a w i t c h (12) compared EPTC p e r s i s t e n c e i n s o i l s w i t h o u t p r e v i o u s EPTC t r e a t m e n t ( n o n - h i s t o r y s o i l ) t o s o i l s t r e a t e d w i t h EPTC ( E P T C - h i s t o r y ) w i t h i n t h e p r e v i o u s year. The s o i l s were a T r i p p v e r y f i n e sandy loam ( A r i d i c H a p l u s t o l l , pH 8.0, 1.0% o r g a n i c m a t t e r ) from S c o t t s b l u f f and a Kennebec s i l (Cumulic H a p l u d o l l s , pH 6.6, 2.A% o r g a n i c m a t t e r ) from Lincoln. Following i n c o r p o r a t i o n of l^C-carbonyl-EPTC, CO^ e v o l u t i o n was measured d u r i n g a 56-day i n c u b a t i o n a t 75% m o i s t u r e h o l d i n g c a p a c i t y and 25C. G r e a t e r * \X) e v o l u t i o n i n d i c a t e d more r a p i d EPTC d e g r a d a t i o n i n E P T C - h i s t o r y s o i l ( F i g u r e 1 ) . The t h r e e day l a g phase o b s e r v e d i n n o n - h i s t o r y Kennebec s o i l was s i g n i f i c a n t l y reduced i n t h e E P T C - h i s t o r y s o i l . The i n i t i a l l a g phase was n o t s i g n i f i c a n t l y reduced i n t h e T r i p p s o i l a l t h o u g h t h e r a t e o f ^ C O ^ e v o l u t i o n was g r e a t e r a f t e r 9 days. The r e d u c t i o n i n l a g phase and g r e a t e r ^ C 0 2 e v o l u t i o n showed t h a t p r e v i o u s EPTC e x p o s u r e e n a b l e d s o i l m i c r o o r g a n i s m s t o more r a p i d l y degrade EPTC i n subsequent application. ?



26

E N H A N C E D BIODEGRADATION O F PESTICIDES IN T H E E N V I R O N M E N T

In a f i e l d s t u d y ( 5 , 12) EPTC was a p p l i e d a t 6.7 kg/ha and i n c o r p o r a t e d i n t o E P T C - h i s t o r y and n o n - h i s t o r y Kennebec s o i l . Soil samples were a n a l y z e d o v e r a 50-day p e r i o d f o r r e s i d u a l EPTC. EPTC was degraded more r a p i d l y i n t h e E P T C - h i s t o r y s o i l a f t e r t h e f i r s t r a i n f a l l on day 16 ( F i g u r e 2 ) . EPTC had an a p p a r e n t h a l f - l i f e o f a p p r o x i m a t e l y 9 days as compared t o 18 days i n t h e n o n - h i s t o r y s o i l . These d a t a c o n f i r m e d t h e l a b o r a t o r y experiment and i n d i c a t e d t h a t reduced EPTC a c t i v i t y c o u l d be a t t r i b u t e d t o more r a p i d d e g r a d a t i o n when a p p l i e d i n c o n s e c u t i v e y e a r s . An a d d i t i o n a l s t u d y (1^3) was c o n d u c t e d t o determine i f enhanced d e g r a d a t i o n c o u l d be i n d u c e d i n t h e l a b o r a t o r y . EPTC and b u t y l a t e were a p p l i e d t o Kennebec s o i l w i t h no p r i o r c a r b a m o t h i o a t e h i s t o r y and r e s i d u a l c o n c e n t r a t i o n s d e t e r m i n e d over a 48-day p e r i o d . The a p p l i c a t i o n and a n a l y t i c a l c y c l e was r e p e a t e d t h r e e t i m e s . One a p p l i c a t i o n o f EPTC was s u f f i c i e n t t o cause t h e maximum d e g r a d a t i o n r a t e o f a subsequent dose ( F i g u r e 3 ) . B u t y l a t e d e g r a d a t i o n i n c r e a s e d a f t e r each b u t y l a t e r e a p p l i c a t i o n but t h e d e g r a d a t i o n r a t e f o r b u t y l a t e remained lower t h a n f o r EPTC. The s o i l enhancement p a t t e r n d i f f e r e d between t h e two h e r b i c i d e s and s u g g e s t e d some d i f f e r e n c e i n t h e i r s u s c e p t i b i l i t y t o cause o r undergo enhanced d e g r a d a t i o n . Cross-Adaptation. To d e t e r m i n e i f o t h e r c a r b a m o t h i o a t e h e r b i c i d e s would degrade more r a p i d l y i n s o i l s e x h i b i t i n g enhanced EPTC d e g r a d a t i o n , t h e d e g r a d a t i o n o f EPTC, and two s i m i l a r c a r b a m o t h i o a t e s , b u t y l a t e and v e r n o l a t e ( S - p r o p y l d i p r o p y l c a r b a m o t h i o a t e ) , were m o n i t o r e d f o r 44 days f o l l o w i n g a p p l i c a t i o n s t o n o n - h i s t o r y and E P T C - h i s t o r y Kennebec s o i l ( 1 3 ) . Both v e r n o l a t e and EPTC had h a l f - l i v e s o f 3 days i n E P T C - h i s t o r y s o i l compared t o 17 and 13 days, r e s p e c t i v e l y , i n n o n - h i s t o r y s o i l ( F i g u r e 4). A s i n g l e carbon i n c r e a s e i n t h e S - a l k y l group ( v e r n o l a t e ) d i d not appear t o s i g n i f i c a n t l y i n f l u e n c e m i c r o b i a l u t i l i z a t i o n . B u t y l a t e d e g r a d a t i o n was more r a p i d i n E P T C - h i s t o r y s o i l t h a n i n nonh i s t o r y s o i l , but t h e d i f f e r e n c e was l e s s than t h a t f o r EPTC o r vernolate. S u b s t i t u t i o n o f t h e N - d i i s o b u t y l group f o r t h e EPTC Nd i p r o p y l may have p a r t i a l l y d e c r e a s e d a c c e l e r a t e d u t i l i z a t i o n by EPTC-adapted m i c r o o r g a n i s m s . Enhanced d e g r a d a t i o n s p e c i f i c i t y has been r e p o r t e d f o r carbamate i n s e c t i c i d e s a l s o ( 1 4 ) . Carbamothioate Extender. F i e l d o b s e r v a t i o n s ( 6 , 15-17) i n d i c a t e d t h a t d i e t h o l a t e e x t e n d e r i n c r e a s e d t h e e f f i c a c y o f EPTC and b u t y l a t e in EPTC-history s o i l . The e f f e c t o f d i e t h o l a t e on EPTC and b u t y l a t e p e r s i s t e n c e was m o n i t o r e d f o r 50 days a f t e r a p p l i c a t i o n t o two EPTCh i s t o r y and n o n - h i s t o r y s o i l s . The E P T C - h i s t o r y s o i l s had t h r e e and e i g h t y e a r s o f p r e v i o u s EPTC a p p l i c a t i o n . EPTC and b u t y l a t e were degraded more r a p i d l y i n t h e E P T C - h i s t o r y s o i l , but EPTC degraded f a s t e r than b u t y l a t e ( F i g u r e s 5 and 6 ) . D i e t h o l a t e i n c r e a s e d EPTC p e r s i s t e n c e i n E P T C - h i s t o r y s o i l but n o t i n n o n - h i s t o r y s o i l . An i n c r e a s e i n b u t y l a t e p e r s i s t e n c e i n the presence of d i e t h o l a t e i n b o t h E P T C - h i s t o r y and n o n - h i s t o r y s o i l s s u g g e s t e d t h a t d i e t h o l a t e had an e f f e c t t h a t was n o t l i m i t e d t o t h e EPTC-adapted m i c r o o r g a n i s m s . The mechanism o f d i e t h o l a t e a c t i o n was u n c l e a r s i n c e i t d i d n o t e x t e n d EPTC p e r s i s t e n c e i n t h e n o n - h i s t o r y s o i l .


3.

ROETHETAL.


0 O


1

^

TIME KENNEBEC S O I L

(days) •

TRIPP SOIL • o\o Figure 1. Degradation of 14C-EPTC in two soils with (dashed line) and without (solid line) previous E P T C application. (Reprinted with permission from ref. 12. Copyright 1982 Weed Science.)


27


28

ENHANCED BIODEGRADATION O F PESTICIDES IN T H E ENVIRONMENT

Time

(Days)

Figure 3. E P T C degradation in a Kennebec silt loam soil during the first, second, and third exposures to EPTC. The reapplication interval was 50 days. (Reprinted with permission from ref. 13. Copyright 1983 Weed Science.)

0

10

20

Time

30

40

50

60

(Days)

Figure 4. Degradation of butylate, E P T C , and vernolate in a Kennebec silt loam soil with eight annual applications of E P T C (dashed lines) or without previous E P T C applications (solid lines). (Reprinted with permission from ref. 13. Copyright 1983 Weed Science.)



3. ROETH ET AL.

0

29


10

20

30

Time

40

50

(Days)

Figure 5. Dietholate(D) effect on butylate(B) and EPTC(E) degradation in a Hastings silt loam soil with three previous E P T C applications. (Reprinted with permission from ref. 13. Copyright 1983 Weed Science.)

Treatments :

EPTC

o.i

I 0

I 10

I 20

Time

Lj 30

EPTC

I 40

50

(Days)

Figure 6. Dietholate effect on E P T C degradation in Kennebec silt loam soil with (dashed line) and without (solid line) previous E P T C applications.


30

E N H A N C E D BIODEGRADATION O F PESTICIDES IN T H E E N V I R O N M E N T


C o n t r o l l e d S t u d i e s . T h r e e f i e l d s i t e s were e s t a b l i s h e d i n 1981 t o more a c c u r a t e l y examine enhanced c a r b a m o t h i o a t e d e g r a d a t i o n i n s o i l s w i t h c o n t r o l l e d h e r b i c i d e h i s t o r i e s (18-20). S o i l s and s i t e s i n c l u d e d a Sharpsburg s i l t y c l a y loam a t Mead ( T y p i c A r g i u s t o l l , pH 6.4, 2.9% o r g a n i c m a t t e r ) , C r e t e s i l t y c l a y loam ( U d i c A r g i u s t o l l , pH 6.6, 2.7% o r g a n i c m a t t e r ) a t C l a y C e n t e r , and a T r i p p v e r y f i n e sandy loam a t S c o t t s b l u f f . S o i l s a t each l o c a t i o n were a n n u a l l y c r o p p e d t o c o r n and t r e a t e d w i t h t h e same a n n u a l p e s t i c i d e t r e a t m e n t s from 1981 t h r o u g h 1985. No c a r b a m o t h i o a t e p e s t i c i d e s had been p r e v i o u s l y applied. One a p p l i c a t i o n o f EPTC o r b u t y l a t e was s u f f i c i e n t t o i n d u c e enhanced d e g r a d a t i o n o f both h e r b i c i d e s a p p l i e d t h e f o l l o w i n g y e a r (19, 2 1 ) . A t C l a y C e n t e r , EPTC d e g r a d a t i o n was most r a p i d i n v e r n o l a t e - h i s t o r y s o i l f o l l o w e d by E P T C - h i s t o r y s o i l ( F i g u r e 7 ) . EPTC was degraded a t an i n t e r m e d i a t e r a t e i n b u t y l a t e - h i s t o r y o r carbofuran (2,3-dihydro-2,2-dimethyl-7 benzofuranyl methylcarbamate)history soils. P r e v i o u s c a r b o f u r a n use d i d n o t r e d u c e EPTC performance a t C l a y C e n t e r i n 1984 (J^9). P r i o r s o i l treatment with atrazine (6-chloro-N-ethyl-N -(l-methylethyl)-l,3,5-triazine-2,4diamine), cyanazine ( 2 - [ [ 4 - c h l o r o - 6 - ( e t h y l a m i n o ) - l , 3 , 5 - t r i a z i n - 2 - y l ] ] amino]-2-methylpropanenitrile), metolachlor (2-chloro-N-(2-ethyl-6methylphenyl)-N-(2-methoxy-l-methylethyl)acetamide), a l a c h l o r (2chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide) or c y c l o a t e ( S - e t h y l c y c l o h e x y l e t h y l c a r b a m o t h i o a t e ) d i d n o t a f f e c t EPTC degradation. A t S c o t t s b l u f f , EPTC d e g r a d a t i o n was e q u a l l y enhanced i n E P T C - h i s t o r y , v e r n o l a t e - h i s t o r y , o r b u t y l a t e - h i s t o r y s o i l s , but was n o t a f f e c t e d by t h e o t h e r p e s t i c i d e s . 1

The degree t o which c a r b a m o t h i o a t e h e r b i c i d e s cause m i c r o b i a l a d a p t a t i o n depends on s p e c i f i c h e r b i c i d e s t r u c t u r e (,19, 2_1, 2 2 ) . V e r n o l a t e and EPTC have s i m i l a r s t r u c t u r e s and s o i l e x p o s u r e t o e i t h e r h e r b i c i d e f u l l y a f f e c t e d the degradation of the other. B u t y l a t e has a s t r u c t u r e somewhat d i f f e r e n t than v e r n o l a t e and EPTC and i t s d e g r a d a t i o n p a t t e r n was o n l y m o d e r a t e l y a f f e c t e d by p r i o r u s e of EPTC and v e r n o l a t e . C y c l o a t e has a c y c l o h e x a n e m o i e t y t h a t makes i t u n i q u e from b u t y l a t e , EPTC, and v e r n o l a t e . The d e g r a d a t i o n r a t e of c y c l o a t e was n o t i n f l u e n c e d by p r e v i o u s s o i l exposure t o e i t h e r EPTC, v e r n o l a t e , o r b u t y l a t e ( 2 2 ) , n o r has p r i o r c y c l o a t e t r e a t m e n t i n c r e a s e d t h e d e g r a d a t i o n r a t e o f t h e l a t t e r c a r b a m o t h i o a t e s (19, 21). EPTC and b u t y l a t e s u l f o x i d e s a r e i n i t i a l m e t a b o l i t e s o f EPTC and butylate degradation. EPTC and b u t y l a t e s u l f o x i d e s i n d u c e d enhanced d e g r a d a t i o n o f t h e i r r e s p e c t i v e p a r e n t compounds ( F i g u r e 8) ( 1 9 ) . P r e t r e a t m e n t o f t h e s o i l w i t h e i t h e r EPTC s u l f o x i d e o r b u t y l a t e s u l f o x i d e caused c r o s s - e n h a n c e d d e g r a d a t i o n o f b u t y l a t e o r EPTC. The d e g r e e and d u r a t i o n o f enhanced EPTC d e g r a d a t i o n i n s o i l s v a r i e d w i t h l o c a t i o n and t h e number o f y e a r s t r e a t e d w i t h EPTC ( 2 3 ) . One p r i o r EPTC a p p l i c a t i o n a t C l a y C e n t e r and S c o t t s b l u f f was s u f f i c i e n t t o cause enhanced-EPTC d e g r a d a t i o n . A t S c o t t s b l u f f , 18 months a f t e r t h e second a n n u a l EPTC a p p l i c a t i o n enhanced EPTC degradation d i d not occur. A t C l a y C e n t e r , s o i l w i t h one p r e v i o u s EPTC t r e a t m e n t c o m p l e t e l y l o s t i t s a b i l i t y t o r a p i d l y degrade EPTC a f t e r 24 months. S o i l w i t h two p r i o r EPTC t r e a t m e n t s d i d n o t f u l l y


3. ROETH ET AL.

31


Π •

Clay

Center

Scottsbluff


111

Figure 7. E P T C degradation in soil from two locations where various pesticides were applied for three consecutive years. Initial concentration was 6 ppm and samples were incubated for 3 days at C C and 4 days at SB. Non-history control=100%. Previous field treatment to retreatment interval was six months.


32



100

I

100

1 EPTC

• • I Butylate

Previous

Treatment

Figure 8. Butylate and E P T C degradation in Crete silty clay loam soil following previous exposure to butylate, E P T C , and their sulfoxides. Initial concentration was 6 ppm and samples were incubated for 3 days. Non-history control had 4 ppm remaining.


3. ROETH ET AL.


33


r e v e r t t o a normal d e g r a d a t i o n r a t e u n t i l a p p r o x i m a t e l y 30 months a f t e r t h e l a s t EPTC a p p l i c a t i o n . The i n i t i a l a d d i t i o n o f d i e t h o l a t e t o EPTC improved g r a s s c o n t r o l and r e d u c e d t h e r a t e o f EPTC d e g r a d a t i o n i n s o i l s e x h i b i t i n g enhanced EPTC d e g r a d a t i o n ( Ii6). However, a f t e r m u l t i p l e a n n u a l a p p l i c a t i o n s of d i e t h o l a t e p l u s EPTC, a c c e l e r a t e d d e g r a d a t i o n o f EPTC was a g a i n o b s e r v e d (24, 2 5 ) . S e v e r a l e x p e r i m e n t s have i n d i c a t e d t h a t r e p e a t e d a p p l i c a t i o n o f d i e t h o l a t e d i d n o t i n d u c e enhanced d i e t h o l a t e d e g r a d a t i o n (1Λ, 2 6 ) , s u g g e s t i n g t h a t d e g r a d e r s may have adopted an a l t e r n a t i v e d e g r a d a t i o n pathway. Fonofos (O-ethyl-S-phenylether phosphonodithioate) i n s e c t i c i d e and SC-0058 [ S - e t h y l d i - ( 3 - c h l o r a l l y l ) c a r b a m o t h i o a t e ] an e x p e r i m e n t a l e x t e n d e r , have a l s o reduced t h e d e g r a d a t i o n o f EPTC i n s o i l s e x h i b i t i n g enhanced EPTC d e g r a d a t i o n (27, 2 8 ) . F o n o f o s was s i m i l a r t o d i e t h o l a t e i n t h a t enhanced d e g r a d a t i o n o f EPTC was a g a i n o b s e r v e d a f t e r r e p e a t e d annual a p p l i c a t i o n s o f EPTC plus fonofos. SC-0058 was e f f e c t i v e i n s l o w i n g EPTC d e g r a d a t i o n i n s o i l s p r e v i o u s l y t r e a t e d w i t h EPTC, EPTC + d i e t h o l a t e , EPTC + f o n o f o s , and EPTC + SC-0058. A t C l a y C e n t e r , EPTC d e g r a d a t i o n , though enhanced i n a l l E P T C - h i s t o r y s o i l s , was s l o w e r i n s o i l w i t h EPTC + S C - 0 0 5 8 - h i s t o r y than i n s o i l s w i t h EPTC o r EPTC + d i e t h o l a t e h i s t o r i e s (28). D i e t h o l a t e , f o n o f o s , o r SC-0058 d i d n o t extend t h e p e r s i s t e n c e o f EPTC i n n o n - h i s t o r y s o i l s and were more e f f e c t i v e i n r e d u c i n g enhanced EPTC d e g r a d a t i o n i n s o i l from S c o t t s b l u f f t h a n from C l a y C e n t e r ( 2 8 ) . T h e r e was a l s o a tendency t o have a reduced l e v e l o f enhanced EPTC d e g r a d a t i o n i n S c o t t s b l u f f s o i l when t h e t r e a t m e n t h i s t o r y i n c l u d e d an e x t e n d e r w i t h EPTC compared t o EPTC w i t h o u t an e x t e n d e r (21^). A p o s s i b l e e x p l a n a t i o n f o r g r e a t e r extender e f f e c t i v e n e s s a t S c o t t s b l u f f t h a n a t C l a y C e n t e r i s t h a t t h e EPTC-degrading m i c r o o r g a n i s m p o p u l a t i o n i s p r o b a b l y lower a t S c o t t s b l u f f ( 2 8 ) . A h i g h e r p o p u l a t i o n o f EPTC-degraders may be a b l e t o degrade t h e extender f a s t e r . Tarn e t a l . (29) r e p o r t e d t h a t t h e i n h i b i t o r y e f f e c t of d i e t h o l a t e was dependent on d i e t h o l a t e c o n c e n t r a t i o n and t h a t an E P T C - d e g r a d a t i o n p r o f i c i e n t b a c t e r i a c o u l d degrade d i e t h o l a t e . E n v i r o n m e n t a l f a c t o r s such as water and temperature have an e f f e c t on EPTC p e r s i s t e n c e . The r a t e o f EPTC d e g r a d a t i o n i n S c o t t s b l u f f s o i l was m o i s t u r e dependent below 25% m o i s t u r e h o l d i n g c a p a c i t y but independent above t h a t ( 9 ) . EPTC d e g r a d a t i o n was more r a p i d a t 15 and 25C than a t 5C i n a s i l t loam s o i l . If soil temperature and m o i s t u r e were i n c r e a s e d t o 37C and f i e l d c a p a c i t y f o r a week b e f o r e EPTC was added t o an E P T C - h i s t o r y s o i l , no enhanced d e g r a d a t i o n was o b s e r v e d . An EPTC-degrading b a c t e r i a l i s o l a t e was shown t o l o s e i t s d e g r a d i n g p l a s m i d a f t e r i n c u b a t i o n a t 32° C f o r 16 h r . ( 3 0 ) . The s o i l and i t s environment have c o n s i d e r a b l e i n f l u e n c e on EPTC d e g r a d a t i o n and a r e p r o b a b l y r e s p o n s i b l e f o r much o f t h e d i f f e r e n c e s i n EPTC d e g r a d a t i o n r a t e s o b s e r v e d a t d i f f e r e n t l o c a t i o n s i n Nebraska and e l s e w h e r e (31_, 3 2 ) . Coping w i t h Enhanced D e g r a d a t i o n . Combinations o f a t r a z i n e w i t h EPTC or b u t y l a t e have been v e r y e f f e c t i v e f o r c o n t r o l l i n g g r a s s e s i n c o r n


34

ENHANCED BIODEGRADATION OF PESTICIDES IN T H E

ENVIRONMENT


even when enhanced d e g r a d a t i o n has r e n d e r e d t h e c a r b a m o t h i o a t e s i n e f f e c t i v e when used a l o n e ( T a b l e I I ) . S i n c e the c a r b a m o t h i o a t e h e r b i c i d e s a r e o f t e n combined w i t h a t r a z i n e f o r maximum weed c o n t r o l , t h e s e h e r b i c i d e c o m b i n a t i o n s o f t e n mask enhanced d e g r a d a t i o n e x c e p t where a t r a z i n e - t o l e r a n t weeds such as s h a t t e r c a n e and w i l d p r o s o m i l l e t (Panicum m i l l i a c e u m L.) a r e p r e s e n t . The use o f h e r b i c i d e c o m b i n a t i o n s i s an e f f e c t i v e s t r a t e g y f o r c o p i n g w i t h enhanced d e g r a d a t i o n as l o n g as both h e r b i c i d e s a r e not m u t u a l l y a f f e c t e d and p r o v i d e complementary c o n t r o l .

T a b l e I I . Combinations o f h e r b i c i d e s f o r g r a s s c o n t r o l i n c o r n a t Clay Center, 1986-89. E v a l u a t i o n s were made about f o u r weeks a f t e r p l a n t i n g Herbicide

lb/A

% Weed Control

Atrazine EPTC EPTC + a t r a z i n e Butylate Butylate + atrazine

3.0 4.0 4.0

+

1.5

4.0

+

1.5

94 26 88 4.020 91

lsd

^ Weed was

(.05)

p r i m a r i l y green f o x t a i l

15

[Setaria v i r i d i s

( L . ) Beauv.]

Two-year h e r b i c i d e r o t a t i o n s which i n c l u d e EPTC one y e a r and a n o t h e r h e r b i c i d e i n the a l t e r n a t e y e a r have k e p t EPTC more e f f e c t i v e t h a n when EPTC was a p p l i e d e v e r y y e a r ( T a b l e ΠΙ ). The p a r t i c u l a r a l t e r n a t e h e r b i c i d e d e t e r m i n e s the degree of e f f e c t i v e n e s s . T h i s may be r e l a t e d t o the degree of weed c o n t r o l o b t a i n e d i n t h e a l t e r n a t e y e a r (weed seed bank e f f e c t ) r a t h e r t h a n any d i r e c t e f f e c t on enhanced d e g r a d a t i o n , though the l a t t e r i s p o s s i b l e . The c a r b a m o t h i o a t e c y c l o a t e , though t h e most e f f e c t i v e a l t e r n a t e h e r b i c i d e o f t h e f o u r t e s t e d , i s n o t r e g i s t e r e d f o r use i n c o r n . R o t a t i o n of h e r b i c i d e c o m b i n a t i o n s such as EPTC p l u s a t r a z i n e and c y a n a z i n e p l u s a t r a z i n e would be e f f e c t i v e i n c o n t r o l l i n g weeds i n many s i t u a t i o n s .


3. ROETH ET AL. Table

III.

annually

Green f o x t a i l or

w e r e made

35


in

rotation

about

four

control at

Clay

weeks

in

corn with

Center,

after

planting

across

herbicides

1985-88.

applied

Evaluations

and have

been

averaged

years

Two-Year Herbicide ^ Rotation ^ Control

With

Each Herbicide

C

Ε

M

Β

A

96

17

40

-

-

(control) 23

74

E-C

72

83

E-M

87

E-B

50

E-A

64


Not

rotated

First in

application

each

98

-

86

58 48

year lsd

(.05)

"I

Ε = EPTC,

2

Treatments

C =

= 15 cyanazine,

were

M =

initiated

cycloate,

in

Β = butylate,

A =

alachlor

1981.

Acknowledgments Special Tuxhorn, We

also

appreciation and

acknowledge

assistants, research

is

extended

ICI Americas and

results

the

for

help

colleagues with

us

to

their of

who

Brent

many

growers,

aided,

throughout

Bean,

Tim Obrigawitch,

contributions

this

extension

counselled

these

to and

Gary

research.

agents,

shared

their

studies.

Literature Cited 1. Martin, A. R.; Roeth, F. W. 1978. No. Cent. Weed Cont. Conf. Proc. 33:108-109. 2. Martin, A.R.; Roeth, F.W. No. Cent. Weed Cont. Conf. Proc. 1979. 34, 51. 3. Roeth, F. W.; Martin, A. R. No. Cent. Weed Cont. Conf. Proc. 1979, 34, 51. 4. Roeth, F. W.; Wilson, R. G . , Martin, A. R.; Shea, P. J . Weed Tech. 1989, 3, 24-29. 5. Obrigawitch; T. T . , Martin, A. R.; Roeth, F. W. No. Cent. Weed Cont. Conf. Proc. 1980, 35, 20. 6. Obrigawitch; T. T . ; Roeth, F. W.; Martin, A. R.; Wilson, R. G. Weed Sci. 1982, 30, 417-422.



36


7. Obrigawitch; T . T . , Martin, A. R.; Roeth, F. W. No. Cent. Weed Cont. Conf. Res. Rep. 1980, 37, 196-198. 8. Roeth, F. W.; Obrigawitch, T. T . ; Martin, A.R. No. Cent. Weed Cont. Conf. Res. Rep. 1980 37, 99-201. 9. Wilson, R. G.; Martin, A. R.; Roeth, F. W. Weed Cont Conf. Proc. 1980, 35, 77. 10. Harvey, R. G.; Dekken, J . H . ; Fawcett, R. S.; Roeth, F. W.; Wilson, R. G. Weed Tech. 1987, 1, 341-49. 11. Roeth, F. W. Reviews of Weed Sci. 1986, 2, 45-65. 12. Obrigawitch; T. T . , Wilson, R. G . , Martin, A. R.; Roeth, F. W. Weed Sci. 1982, 30, 175-181. 13. Obrigawitch, T. T . ; Martin, A. R.; Roeth, F. W. Weed Sci. 1983, 31, 187-192. 14. Racke, K. D.; Coats, J . R. J . Agric. Food Chem. 1988, 36, 106772. 15. Obrigawitch; T. T . , Martin, A. R.; Roeth, F. W. No. Cent. Weed Cont. Conf. Proc. 1981, 36, 127. 16. Obrigawitch; T. T . , Martin, A. R.; Roeth, F. W. No. Cent. Weed Cont. Conf. Res. Rep. 1981, 38, 166. 17. Roeth, F. W.; Obrigawitch, T. T . ; Martin, A. R. No. Cent. Weed Cont. Conf. Res. Rep. 1981, 38, 164-165. 18. Bean, B. W.; Roeth, F. W.; Martin, A. R.; Wilson, R. G. No. Cent. Weed Cont. Conf. Proc. 1984, 39. 19. Bean, B. W.; Roeth, F. W.; Martin, A. R.; Wilson, R. G. Weed Sci. 1988, 36, 70-77. 20. Martin, A.R.; Roeth, F W. No. Cent. Weed Cont. Conf. Res. Rep. 1983. 40, 200. 21. Tuxhorn, G. L.; Roeth, F. W.; Martin, A. R.; Wilson, R. G. Weed Sci. 1986, 34, 961-965. 22. Wilson, R. G. Weed Sci. 1984, 32, 264-268. 23. Bean, B. W.; Roeth F. W.; Martin, A. R.; Wilson, R. G. Weed Sci. 1988 36, 524-530. 24. Harvey, R. G.; Mcnevis, G. R.; Albright, J . W.; Kozak, M. E. Weed Sci. 1986, 34, 773-80. 25. Rudyanski, W. J.; Fawcett, R. S.; McAllister, R. S. Weed Sci. 1987, 35, 68-74. 26. Wilson, R. G.; Rodebush, J . E. Weed Sci. 1987, 35, 289-94 27. Bean, B. W.; Roeth, F. W.; Martin, A. R.; Wilson, R. G. No. Cent. Weed Cont. Conf. Proc. 1985, 40, 11. 28. Bean, B. W.; Roeth, F. W.; Martin, A. R.; Wilson, R. G. Weed Science. 1990. 29. Tam, A . C . ; Buhki, R. M.; Kahn, S. U. J . Agric. Food Chem. 1988, 36, 654-57. 30. Tam, A. C . ; Buhki, R. M.; Khan, S. U. Appl. Environ. Microbiol. 1987, 53, 1088-93. 31. McCusker, V. W.; Skipper, H. D.; Zublema, J . P.; Gooden, D. T. Weed Sci. 1988, 36, 818,23. 32. Harvey, R. G. Weed Sci. 1987, 35, 683-89. RECEIVED February 21, 1990


Enhanced Carbamothioate Herbicide Degradation - ACS Symposium

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