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Chapter 20

Enhanced Biodegradation of Pesticides in the Environment Downloaded from pubs.acs.org by UNIV OF CALIFORNIA SANTA BARBARA on 07/09/18. For personal use only.

Implications of Enhanced Biodegradation for the Use and Study of Pesticides in the Soil Environment Kenneth D. Racke Environmental Chemistry Laboratory, DowElanco, 9001 Building, Midland, MI 48641-1706

Microbial adaptation for biodegradation is a common microevolutionary phenomenon that occurs wherever biodegradable pesticides or other xenobiotics contact microbial populations. The accelerated biodegradation of pesticides in agricultural systems has certainly had a substantial impact on pesticide users, researchers, and the agrochemicals industry. Major advances in our understanding of the theoretical and practical aspects of enhanced biodegradation have come about as a result of the recent flurry of research activity generated by contemporary occurrences associated with pest control failure. Future challenges and opportunities that remain relate to the development of conceptual predictive models, the design of biodegradable yet adaptation-resistant pesticides, clarification of the soil microbial ecology of biodegradation, and the application of adapted microbial strains for environmental decontamination and hazardous waste detoxification.

Enhanced

pesticide

interest

and concern.

outlined

the

involved,

biodégradation

tion,

In the

of

have

detailed

occurs to

way

the

the

place the need

enhanced recent that to

its

true

the

coping

of

been

and

chemical

with

enhanced

The purpose

pesticide

impact

have

be

of

this

biodégradation

enhanced

made,

and

in

biodégradathe

future

addressed.

Biodégradation impact

of

enhanced

i n a g r i c u l t u r a l systems been

of

much

systematically

microbiological means

i n agroecosystems.

advances that

Enhanced

problem has

regarding

generated

by d i s c u s s i n g

frustrating

pesticides

recently chapters

and d i s c u s s e d

is

challenges

Impact a

it

major r e s e a r c h

research The

as

chapter

perspective

has

The p r e c e e d i n g

phenomenon,

interactions concluding

biodégradation

is

difference

significance.

of

very

biodégradation hard

opinion

F o r example,

to

quantify.

that an

0097-6156/90/0426-0269$06.00/0 © 1990 American Chemical Society

has

of Part

of

existed

industry

spokesman

270

ENHANCED BIODEGRADATION O F PESTICIDES IN T H E ENVIRONMENT

was

quoted

as

interesting problem.

saying:

I n what (I).

private

and p u b l i c

Despite

enhanced

(2,3,4).

From a

we're

a l l . . . " of

"From a

problem.

seeing, type

of

sectors

have

felt

biodégradation

degradation:

"The c a s e

this

phenomenon

practices

in

enhanced

certain

Pesticide

Users. been

have

by

the

degradation, as

Actual

are

within

the

number

used

in

no

1985

have

Asia,

are

rare

of

of

enhanced

enhanced show

that

affected

by

that of

rootworm

years,

the

greatest

(0-18%)

indicates

1983

and

that

they

perceived

378

gave

1984

Analyses

60% o f

were of

significant herbicides weed o r

correlation detected

(9).

because

directly

the

marauding

insects

there

certainly

of

the

products.

failures

both

of

highly

a

taken

This

new

of

is

by s u r p r i s e

Pesticide

Manufacturers.

Pesticide

adversely

affected

occurrence

products.

One o f

products

or

by the

sales

the most due

to

direct real

a of

weed

these control impact

always caused

reality,

reliable pest (e.g.,

due

estimate.

not

often

isofenphos)

in

by and the

and

control carbofuran)

often

have,

(10).

manufacturers of

enhanced

adverse or

corn.

among g r o w e r s

supply

pesticides

(e.g.,

in

found

to

in

indicated

economic

is

p a r t i a l l y because

reliable

pesticides

everyone

confidence to

weeds

competition is

Nebraska

users

difficult

or

control

Central

and poor

perception

industry

A similar

weed

actual

of

be

degradation

reduction

damage

But

loss

long-used,

touted

seemingly,

crop yield

of

very

by

behavior may

fields

enhanced

are

observed

agrochemicals

efficacious

of

1984,

failures

failures

butylate

control

insecticide growers

For

(8).

In South

measurements

and weeds. been

the

failure

actual to

efficacy

any

Iowa

during

variable

laboratory assay)

However, control

proportional

has

by

of

in

360

the

5 years.

from surveyed

between

of

rootworm

19% o f

carbamothioate

the

adapted

growers

many f a c t o r s

a n d 40% o f

with

taken

of

insecticides

results.

EPTC u s e r s

samples

insect

for

distinct

dissatisfied

soil (as

performance

more

that

rootworm c o n t r o l

Nebraska farmers

of

the

that

boundries!

percentage

but

diverse potatoes

observations

A survey

preceeding

enhanced

such

implies

with

an average

them

insect,

been

by

and

these

percentage

regarding experiences

compounds of

national

the

for

on

of

have

caused

avocados, East)

degradation

and r e l y

ravages

documented

degradation.

isofenphos,

performance

of

been

enhanced

failures

d i s t r i b u t i o n of

12% d u r i n g t h e

5

the

from the

onions,

23% f o r

ability

Who h a s

pesticides

The M i d d l e

respecters

performance

of

been

was

is

of

protection

agroecosystems

control

beets,

revealed

poor last

influencing

and

pest

sugar

estimates

an average

This

the

occurrence

clearly

crop

at

in

impact

reviewer

earlier

in

use

Many d i v e r s e of

Europe,

failures

experienced

survey

substantial one

(4).

great

impact

contemporary

affected

protection

The g e o g r a p h i c a l

growers

other

of

losers

actually

instances

experiencing

control and

pests.

rice,

America,

area

corn

adversely

significant

and

microorganisms one

had a

an

a

many r e s e a r c h e r s

the

presented

direct

who

effects

corn,

(3,4,5,6,7). (North

to

T h e most

and f u n g a l

touched crops

indeed

agroecosysterns."

growers

economically

weed,

that

is

not

major economic

hyperbole,

statement

histories has

no

this

it's

degradation?

game for

has

recent

standpoint,

standpoint,

there's

this

C o n s i d e r the

natural

theoretical practical

have

results

perceived

also

been

degradation

pest

involves control

of

the

their loss

failures.

20. RACKE The

Midwestern U.S.

supplies removed least

a

litany

from

(4,10). a

related

of

to

remedial

measures.

undergo

investigators in-house

at

effort

impossible

these

projects,

industrial of

as

Gray

well

as

and Joo of

a

that

screening

that

step

have the

efforts

have

for

that

efforts users

revolved

is

soil a

by

the

is

to

rapid companies for

developmental

ignore.

Considerable

means

coping

(17).

in

the

generally

pesticides

necessary of

For

with

example,

by S t a u f f e r

growers

and d e a l e r s ,

entitled

" C o r n Rootworm Management:

1985

contained

biodégradation extension

a

very

a

pesticide

including

a

pair

this

degradation

in

of

an

microbial

problems

have

been

hosted

by S t a u f f e r

effort

has

marketing

products

imply that

susceptible

to

insecticide

seems

all

microbial

one

of

two

known e n h a n c e d the

adaptation

(e.g.,

a

h a v i n g unknown e n h a n c e d

degradation

using

microbial

their

adaptation,

products

degradation

(e.g.,

a

grower

action".).

Unfortunately,

that

they

brochure: this

have need

"

of

grower 2.

The

no

resists

marketing a c t i v i t y

on

industry, seamier

enhanced 1.

types

are

of

Companies

problems

have

equally

brochure:

potential, have

and

by

Companies

sought

(21)

enhanced

conferences

These

products

problem.").

to

of

degradation

this

withresistance

immune t o

Experts"

sponsored use

For

booklet

researchers

strategies:

competitor's

area.

topic

a n d Dow.

involved

of

information

the

the

the

marketing purposes.

involved

with

from of

special

1985

usually

in

have

comely

digestable

informative

and p r i v a t e several

the

T h e more

facilitate

Insights

educational

sought

to

university

is

companies

supply

working

presentation

In a d d i t i o n ,

information for

have

to

d i s t r i b u t e d an

balanced

degradation

considered

and to

researchers

Carbide

by eight

personnel.

be

agrochemicals

around attempts

Union

growers

conducted

demonstrated It

costs of

industrial

exemplified

and r e s e a r c h e r s .

in

products

by

manufactured by other

must

example,

efforts

considerable

been

EPTC c o n t a i n i n g

that

independent

of

who

is

and t e s t i n g

between

side

This

products

herbicide

industrial cost educational

toward p e s t i c i d e

information

soil

reports

work has

of

outside

these

developing

development

to

many

company c a n a f f o r d existing

gone

laboratories,

candidate

to

existing

development

f u n d i n g has

own c a r b a m o t h i o a t e s .

exchange

that

and

of

degradation

the

new

and f o r

(12).

projects

proprietary nature

Stauffer,

of

1985

numerous

of

herbicides

assay

exemplified

(18,19,20).

substantial directed

for

substantial

devoted

extensive

A final

these

no

been

formulation of

inhibitor

of

their

degradation of

consider altered

(16)

t h a n 8% b y

and p u b l i s h e d

that

enhanced

also

the

is

The magnitude

(13,14,15,16).

ongoing to

this

expended.

given

number o f of

potential

(Fisons), (Mobay)

c a r b o f u r a n plummeted

funded

and u n i v e r s i t y

presented

indicate

less

at

include

degradation

biodégradation

been

estimate

susceptibility

enhanced

also

but

to

Products

development

isofenphos

wherein

also

much o f

of

bendiocarb

and

enhanced

ill)

the

Whereas

several

recognized

efforts

of

laboratories

degradation

1977

stages

(Chevron),

i n d u s t r y has

government

to

to

( > 2 0 0 MM $ / y e a r )

products.

degradation

(Shell),

Iowa c o r n ,

enhanced

has

representatives work

in

late

enhanced

due

in

an assessment

to

in

bufencarb

sales

agrochemicals

products

of

market

and f a i l e d

halted

trimethacarb

20% m a r k e t s h a r e

The

or

(Chemagro), loss

insecticide

business

result

c a r b o f u r a n (FMC) use

from

is

a

(BASF),

The

lost

market

p a r t i a l l y as

cloethocarb

rootworm

of

this

fensulfothion

by

271

Implications for Use & Study of Pesticides in Soil

to

"No

marketing

or reassure

worry of

enhanced

microbial has

i n some

cases

272

ENHANCED BIODEGRADATION OF PESTICIDES IN T H E ENVIRONMENT

muddled t h e i s s u e w i t h growers r e g a r d i n g t h e a c t u a l s t a t u s o f enhanced d e g r a d a t i o n problems w i t h s p e c i f i c p e s t i c i d e p r o d u c t s . The R e s e a r c h / E x t e n s i o n Community. U n i v e r s i t y , s t a t e , and f e d e r a l r e s e a r c h e r s and e x t e n s i o n p e r s o n n e l have a l s o been a f f e c t e d by t h e contemporary o c c u r r e n c e o f enhanced d e g r a d a t i o n . The s t a t e e x t e n s i o n s e r v i c e s , which s e r v e as t h e c r i t i c a l l i n k between t h e heady s c i e n t i f i c u n i v e r s i t y r e s e a r c h and the p r a c t i c a l i n f o r m a t i o n a l needs o f growers, have o f t e n f o u n d themselves i n t h e most d i f f i c u l t p o s i t i o n i n r e g a r d t o enhanced d e g r a d a t i o n problems. They a r e t h e ones o f t e n c a l l e d upon t o d e a l w i t h p e s t c o n t r o l f a i l u r e problems and to make s p e c i f i c recommendations r e g a r d i n g ways t o a v o i d o r manage t h e s e problems. P a r t o f the agony o f e x t e n s i o n workers may be a t t r i b u t e d t o a l a c k o f p r o g r e s s on the r e s e a r c h l e v e l . For i n s t a n c e , the e a r l i e s t p u b l i s h e d r e p o r t s o f s t u d i e s e x a m i n i n g t h e p o s s i b i l i t y t h a t enhanced d e g r a d a t i o n was t h e c a u s e o f r e p o r t e d c a r b o f u r a n p e s t c o n t r o l f a i l u r e s i n Midwestern U.S. c o r n p r e s e n t e d c o n f l i c t i n g c o n c l u s i o n s , w i t h some n e g a t i v e (22,23) and some p o s i t i v e (24,25) f i n d i n g s . E x t e n s i o n recommendations o f t e n d i r e c t l y r e f l e c t the l e v e l o f r e s e a r c h u n d e r s t a n d i n g a v a i l a b l e . In t h e e a r l y 1980's t h e s e recommendations s t a r t e d t o a d d r e s s the problem o f enhanced degradation. F o r example, an A p r i l 1982 C o r n Rootworm Management b u l l e t i n from Iowa S t a t e U n i v e r s i t y (26) s t a t e d : " I t i s r e c o g n i z e d t h a t c o n t i n u e d carbamate i n s e c t i c i d e use enhanced t h e speed w i t h which c e r t a i n s o i l m i c r o o r g a n i s m break down Furadan, and t h a t t h i s i s t h e c a u s e o f poor c o n t r o l " . The recommendation t o a v o i d u s i n g c a r b o f u r a n i f i t performed p o o r l y f o l l o w e d . But r e f l e c t i n g t h e l a c k o f p r o o f t h a t organophosphorus i n s e c t i c i d e s c o u l d a l s o undergo enhanced d e g r a d a t i o n , t h i s statement a l s o appeared: " C u r r e n t l y a v a i l a b l e ISU r e s e a r c h d a t a do not i n d i c a t e t h a t c o n t i n u o u s use o f an organophosphate s o i l i n s e c t i c i d e s i g n i f i c a n t l y a f f e c t s t h e performance o f any i n s e c t i c i d e , . . . " . A f t e r the d i s c o v e r y o f enhanced i s o f e n p h o s d e g r a d a t i o n (10) e x t e n s i o n recommendations were m o d i f i e d and r e f l e c t e d the u n c e r t a i n t y r e g a r d i n g t h e a b i l i t y o f any s o i l i n s e c t i c i d e t o m a i n t a i n e f f i c a c y i f used c o n t i n u o u s l y (27,28). It was d u r i n g t h e mid 1980*s t h a t b o t h i n s e c t i c i d e and h e r b i c i d e recommendations s t a r t e d e m p h a s i z i n g t h e r o t a t i o n o r d i s u s e o f p e s t i c i d e s w i t h p r o v e n enhanced d e g r a d a t i o n p o t e n t i a l (27.28,29). R e s e a r c h e r s a t u n i v e r s i t y and government l a b o r a t o r i e s have responded t o enhanced d e g r a d a t i o n by f o c u s i n g c o n s i d e r a b l e r e s e a r c h e f f o r t s on u n r e s o l v e d i s s u e s . R e s e a r c h e r s i n many d i v e r s e d i s c i p l i n e s have become i n v o l v e d as f u n d i n g f o r enhanced d e g r a d a t i o n r e s e a r c h became a v a i l a b l e . One o f the l e a d i n g s p o n s o r s o f enhanced d e g r a d a t i o n r e s e a r c h i n t h e U.S. has been t h e P e s t i c i d e Impact Assessment Program (ΡΙΑΡ) o f the U.S. Department o f A g r i c u l t u r e . A f t e r s p o n s o r i n g a workshop on the problem i n S t . L o u i s i n 1984, t h e PIAP has a l l o c a t e d c o n s i d e r a b l e f u n d i n g t o enhanced d e g r a d a t i o n r e s e a r c h . F o r example, the N o r t h C e n t r a l Region PIAP a l l o c a t e d o v e r $300,000 f o r t h e s e p r o j e c t s between 1982 and 1989 (A.C. Waldron, p e r s o n a l communication). S t a t e f u n d i n g has a l s o been a v a i l a b l e f o r t h i s t y p e o f r e s e a r c h , as e x e m p l i f i e d by p r o j e c t s s u p p o r t e d by t h e N e b r a s k a C o r n Development Board (30), the Iowa C o r n P r o m o t i o n Board (31), and t h e O n t a r i o P e s t i c i d e s A d v i s o r y Committee (32). But t h i s s u p p o r t , a l t h o u g h s i g n i f i c a n t , has o f t e n p r o v e n i n a d e q u a t e f o r t h e t a s k , and f u n d i n g from the a g r o c h e m i c a l s i n d u s t r y has been used t o

20.

RACKE

Implications for Use & Study ofPesticides in Soil

273

f i l l t h i s gap. I n f o r m a t i o n on t h e magnitude o f i n d u s t r i a l s u p p o r t i s unavailable. However, some i d e a o f t h e e x t e n t o f t h i s s u p p o r t c a n be i n f e r r e d from p u b l i c a t i o n acknowledgements t h a t i n c l u d e mention o f BASF (6,33), Dow (34), FMC (23), Mobay (35), S t a u f f e r (36,37,38), and U n i o n C a r b i d e (39) as c o n t r i b u t i n g t o f i n a n c i a l s u p p o r t . The r e s e a r c h e f f o r t s t h a t have been s t i m u l a t e d by t h e phenomenon o f enhanced d e g r a d a t i o n have r e s u l t e d i n t h e c r e a t i o n o f a s u b s t a n t i a l knowledge base r e g a r d i n g m i c r o b i a l a d a p t a t i o n f o r p e s t i c i d e d e g r a d a t i o n and a s s o c i a t e d p e s t c o n t r o l f a i l u r e s . The body o f s c i e n t i f i c l i t e r a t u r e on t h e s u b j e c t has grown r a p i d l y and i s now substantial. Recent r e v i e w s o f enhanced d e g r a d a t i o n and m i c r o b i a l a d a p t a t i o n f o r p e s t i c i d e d e g r a d a t i o n by Kaufman (2) (59 r é f . ) , Kearney and K e l l o g g (40) (108 r é f . ) , Roeth (3) (167 r é f . ) , Sandmann et a l . (41) (161 r é f . ) , S u e t t and Walker (5) (37 r é f . ) , and F e l s o t (4) (117 r e f . ) a t t e s t t o the growth i n p u b l i s h e d i n f o r m a t i o n . In a d d i t i o n t o p u b l i s h e d communication o f r e s e a r c h r e s u l t s , a number o f c o n f e r e n c e s have f a c i l i t a t e d i n f o r m a t i o n exchange. In a d d i t i o n t o U.S. Department o f A g r i c u l t u r e and i n d u s t r y s p o n s o r e d meetings, t h e American Chemical S o c i e t y (1984, 1989), t h e Weed S c i e n c e S o c i e t y o f A m e r i c a (1986), and t h e E n t o m o l o g i c a l S o c i e t y o f A m e r i c a (1984) have s p o n s o r e d s p e c i a l symposia on enhanced d e g r a d a t i o n , and the S o i l S c i e n c e S o c i e t y o f A m e r i c a has been the forum f o r numerous p a p e r s on t h e t o p i c d u r i n g the 1980's. What advances i n our u n d e r s t a n d i n g o f enhanced p e s t i c i d e biodégradation have accompanied t h i s contemporary f l u r r y o f r e s e a r c h activity? Advances i n R e s e a r c h

Understanding

Major advances i n o u r s c i e n t i f i c u n d e r s t a n d i n g o f enhanced d e g r a d a t i o n may be r e l a t e d t o the f o l l o w i n g d e f i n i t i o n o f f e r e d f o r enhanced biodégradation o f a p e s t i c i d e ( o r o t h e r o r g a n i c ) : "Enhanced biodégradation i s the a c c e l e r a t e d r a t e o f p e s t i c i d e d e g r a d a t i o n , by adapted s o i l microorganisms, observed i n s o i l f o l l o w i n g previous a p p l i c a t i o n o f i t or a s i m i l a r p e s t i c i d e . Enhanced d e g r a d a t i o n may r e s u l t i n p e s t c o n t r o l f a i l u r e and c r o p y i e l d r e d u c t i o n . " A c c e l e r a t e d P e s t i c i d e D e g r a d a t i o n Rate. The a c c e l e r a t i o n i n d e g r a d a t i o n r a t e due t o m i c r o b i a l a d a p t a t i o n has been w e l l characterized. F o r p e s t i c i d e s t h a t a r e somewhat e n v i r o n m e n t a l l y u n s t a b l e (e.g., EPTC) the i n c r e a s e i n d e g r a d a t i o n r a t e a s s o c i a t e d w i t h enhanced d e g r a d a t i o n r e d u c e s an i n h e r e n t l y s h o r t s o i l h a l f - l i f e (13 d a y s ) t o an e x t r e m e l y s h o r t one (4 d a y s ) (42). For other p e s t i c i d e s (e.g., i s o f e n p h o s ) , enhanced d e g r a d a t i o n r e s u l t s i n more s p e c t a c u l a r d e c r e a s e s (12 weeks t o