Pesticide Chemistry in the 20th Century - ACS Publications

3 Development of the American Herbicide Industry E. F. A D L E R , W. L. W R I G H T , and G. C. K L I N G M A N

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Lilly Research Laboratories, E l i Lilly and Co., Greenfield, Ind. 46140

From the b e g i n n i n g of r e c o r d e d history, weeds have limited man's food s u p p l y and have imposed a heavy l a b o r b u r d e n . N e a r l y all of e a r l y man's time was no doubt spent in o b t a i n i n g f o o d . N a t u r a l food sources permitted man's survival, even though p e r i o d s of starvation must have been common. From 10,000 B . C . to 6,000 B.C., man began to cultivate c r o p s by primi tive methods ( F i g . 1) ( 1 ) . About 6,000 B.C., he f a s h i o n e d hand-weeding tools. Around 1,000 B.C., a n i m a l - p o w e r e d implements were i n t r o d u c e d . P r i o r to this t i m e , human energy was the s o l e source available f o r weed control. In the 2,900 y e a r s between 1,000 B . C . and 1900 A.D., man l e a r n e d to use a n i m a l s to till the soil and to c o n t r o l weeds. Improved tools l e d to b e t t e r cul tural methods and even g r e a t e r d e c r e a s e s in the human effort r e q u i r e d f o r weed control. By 1920, in this c o u n t r y , perhaps 40% of the energy i n p u t to weed con trol was human, 60% a n i m a l . In the 1920's, tractors were i n t r o d u c e d as new agricultural tools and were u s e d , among o t h e r t h i n g s , to i n c r e a s e the amount of l a n d t h a t one man c o u l d cultivate. By 1947, tractors with cultivators re placed perhaps 70% of the hand and a n i m a l l a b o r f o r m e r l y r e q u i r e d f o r weed control. A f t e r World War I I , modern c h e m i c a l weed c o n t r o l was i n t r o d u c e d . C h e m i c a l h e r b i c i d e s not o n l y reduced the human energy r e q u i r e d , but a l s o reduced the amount of m e c h a n i c a l c u l t i v a t i o n . We e s t i m a t e human energy i n p u t f o r o v e r a l l weed c o n t r o l i n the U n i t e d S t a t e s today at no more than 5%, w i t h o n l y a t r a c e of a n i m a l energy i n p u t ; m e c h a n i c a l , at 40% and d e c l i n i n g ; w i t h h e r b i c i d e s r e s p o n s i b l e f o r the r e m a i n d e r . Thus, the

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Plimmer et al.; Pesticide Chemistry in the 20th Century ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

PESTICIDE CHEMISTRY IN THE 20TH CENTURY


40

Figure 1.

History of weed control

50

10,000 B.C. 6,000 B.C. 1,000 B.C. REMOVAL BY HAND

Figure 2.

PRIMITIVE HAND TOOLS INTRODUCED

1920 A.D.

ANIMAL-POWERED MECHANICALLY IMPLEMENTS POWERED INTRODUCED IMPLEMENTS (TRACTORS) INTRODUCED

1947 AD.

1975 A.D.

CHEMICAL WEED CONTROL INTRODUCED

PRESENT DAY

Crop energy output per man (number of people fed by one farmer)



3.

ALDER ET

AL.

American

Herbicide

41

Industry

h i s t o r y of weed c o n t r o l has seen a s h i f t from the use o f a l l human e f f o r t , to animal power, to petroleump o w e r e d e q u i p m e n t , a n d now to chemical herbicides. U s i n g t h e same t i m e f r a m e s , t h e c r o p e n e r g y o u t p u t p e r man as m e a s u r e d by t h e n u m b e r o f p e o p l e f e d by one farmer i s presented in Figure 2. E a r l y man did w e l l to feed himself. When he b e g a n t o c u l t i v a t e c r o p s , by 6 , 0 0 0 B.C., o n e man was a b l e t o p r o v i d e a l i t t l e m o r e f o o d t h a n he himself could eat. H e n c e , some t i m e was available for fash i o n i n g t o o l s and for other a c t i v i t i e s . By 1,000 B.C., o n e man c o u l d , i n many p a r t s o f t h e w o r l d , feed as many as t h r e e p e o p l e . Again, l e t ' s move a h e a d 2,900 y e a r s t o t h e U n i t e d S t a t e s ; we find t h a t by 1920 one f a r m e r was c a p a b l e of f e e d i n g e i g h t p e o p l e ; by 1947, 16; and t o d a y , a t l e a s t 50 p e o p l e . The m o s t recent of t h e s e advances would have been i m p o s s i b l e without c h e m i c a l weed control. The b e n e f i t s f r o m h e r b i c i d e u s a g e a r e many (Table I ) . Table

Hand

I.

Herbicides

tillage

costs

reduce

Harvest

costs

Mechanical costs

tillage

Grain

Fertilizer

costs

Transportation and storage costs

Irrigation

costs

Crop

losses

yield

drying

costs

Number of laborers required Acres needed production

for

crop

They i n c l u d e a r e d u c t i o n of hand t i l l a g e costs. B e f o r e h e r b i c i d e s , h a n d h o e i n g was regularly practiced in a l l vegetable c r o p s and i n most a g r o n o m i c crops. In vegetable c r o p s , h a n d h o e i n g m i g h t c o s t as much as $300 or more per a c r e f o r the s e a s o n . With h e r b i c i d e s , t o t a l w e e d i n g c o s t s c a n be r e d u c e d t o a s m a l l fraction of t h i s sum. B e f o r e h e r b i c i d e s , 20 h o u r s o f h o e labor t i m e p e r a c r e i n c o t t o n was u s u a l and weedy fields c o u l d r e q u i r e 100 hours. Y o u may have heard that h e r b i c i d e s would not be used i n underdeveloped c o u n t r i e s where l a b o r i s avail a b l e and inexpensive. But our e x p e r i e n c e has been t o the c o n t r a r y . N o w h e r e i n t h e w o r l d do p e o p l e l i k e to



42


p u l l w e e d s b y h a n d a n d move s o i l f o r weed control. The a b o l i s h m e n t o f t h e d r u d g e r y o f s t o o p l a b o r , and the consequent h i g h e r crop y i e l d s a f f o r d e d by h e r b i c i d e s , u l t i m a t e l y b e t t e r s t h e l o tof t h e hoe-hand. It a l s o r e l e a s e s c h i l d r e n t o a t t e n d s c h o o l and w i v e s to b e t t e r t e n d t h e i r f a m i l i e s o r f i n d more p r o f i t a b l e employment. H e r b i c i d e s r e d u c e m e c h a n i c a l t i l l a g e c o s t s (2^) . E a c h y e a r i n t h e U n i t e d S t a t e s , 250 b i l l i o n tons of s o i l a r e moved, much o f i t s e v e r a l t i m e s , i n t i l l a g e and c u l t i v a t i o n o p e r a t i o n s . T h i s amount o f s o i l w o u l d make a r i d g e 100 f e e t h i g h a n d one m i l e w i d e f r o m New Y o r k t o S a n F r a n c i s c o . The movement o f t h i s s o i l each year i s the world's l a r g e s t m a t e r i a l handling operation. At least one-half of this s o i l moving f u n c t i o n i s p r a c t i c e d s o l e l y f o r t h e c o n t r o l of weeds. Herbicides reduce f e r t i l i z e r costs. Weeds a r e in d i r e c t competition w i t h crop p l a n t s f o r n u t r i e n t s from the s o i l . W i t h o u t weed c o n t r o l , f a r m e r s w o u l d be f e r t i l i z i n g t h e crop and t h e weeds. Herbicides reduce i r r i g a t i o n costs. Weeds a r e a l s o i n d i r e c t c o m p e t i t i o n w i t h crop p l a n t s f o r water. Thus, i r r i g a t i o n w a t e r used by weeds i s n o t a v a i l a b l e for the production of a crop. Crop y i e l d l o s s e s due t o weeds v a r y a c c o r d i n g t o the c o m p e t i t i v e n e s s o f t h e c r o p , t h e weeds present, and t h e p o p u l a t i o n d e n s i t y o f t h e w e e d s . Weed c o n t r o l is extremely important t o any good p r o g r a m o f c r o p production. Crop l o s s due t o weed c o m p e t i t i o n c a n be s u b s t a n t i a l (_3) . As an e x a m p l e , i t h a s been estimated t h a t n e a r l y 100 m i l l i o n b u s h e l s of soybeans, or the e q u i v a l e n t o f t h e p r o d u c t i o n f r o m 4,000,000 a c r e s , was l o s t due t o weed c o m p e t i t i o n i n t h e y e a r 1970. Herbicides reduce harvest costs. Weeds o f t e n m a k e i t i m p o s s i b l e t o h a r v e s t a c r o p a n d may r e s u l t i n t o t a l crop f a i l u r e . Weeds w r a p a r o u n d , c l o g , a n d otherwise i n t e r f e r e with harvesting equipment, result ing i n longer running times, greater fuel consumption, and i n c r e a s e d h a r v e s t costs. Herbicides reduce grain drying costs. Fields t h a t a r e f i l l e d w i t h green weeds as t h e crop i s matur ing and d r y i n g r e s u l t i n t h e g r a i n d r y i n g more s l o w l y . Weed s e e d s a n d s t e m s t h a t f i n d t h e i r w a y i n t o t h e grain b i n are usually high i n moisture content. These g r e e n weed p a r t s i n c r e a s e t h e p o t e n t i a l f o r g r a i n s p o i l a g e and t h e c o s t of d r y i n g .



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Herbicides reduce t r a n s p o r t a t i o n and storage costs. A good example o f t h e t r a n s p o r t a t i o n and storage c o s t s o f weed s e e d s was g i v e n b y a C a n a d i a n weed s c i e n t i s t (_1) . He r e p o r t e d that despite herbi c i d e u s a g e a n d g r a i n - c l e a n i n g p r o c e s s e s , 33 r a i l r o a d c a r l o a d s o f weed seeds a r e t r a n s p o r t e d across Canada from e l e v a t o r s t o ports each day. F i n a l l y , h e r b i c i d e s r e d u c e t h e number o f a c r e s needed f o rcrop production. I f , t h r o u g h b e t t e r weed c o n t r o l , we c a n o b t a i n h i g h e r y i e l d s , we c a n r e d u c e the number o f a c r e s r e q u i r e d t o p r o d u c e a g i v e n amount o f f o o d . The h i s t o r y of the use of chemicals f o r vegeta t i o n c o n t r o l goes back t o a n t i q u i t y . We k n o w t h a t t h e Romans s a l t e d t h e f i e l d s o f t h e i r d e f e a t e d Carthagin ian foe. P r o b a b l y s a l t was u s e d much e a r l i e r a s a soil sterilant. The f i r s t r e c o r d e d recommendation o f s o d i u m c h l o r i d e f o r weed c o n t r o l was i n Germany i n 1854 (4·) ( T a b l e I I ) . The n e x t y e a r s u l f u r i c a c i d was recommended and was u s e d f o r s e v e r a l d e c a d e s a r o u n d the world f o r s e l e c t i v e weed c o n t r o l i n c e r e a l s a n d onions. Sodium a r s e n i t e was i n t r o d u c e d i n 1902 by t h e Army C o r p s o f E n g i n e e r s f o r t h e c o n t r o l o f w a t e r hyacinth i n Louisiana. The e f f e c t i v e n e s s o f c a r b o n d i s u l f i d e a s a s o i l f u m i g a n t f o r weed c o n t r o l was discovered i n 1 9 0 6 . I t was used i n H a w a i i , California, and some o f t h e w e s t e r n s t a t e s . The peak usage was r e a c h e d i n I d a h o i n 1936 when 350,000 g a l l o n s w e r e applied. P e t r o l e u m o i l s were used as e a r l y as 1914, and t h e y h a v e b e e n w i d e l y u s e d i n i r r i g a t i o n a n d drainage d i t c h e s i n t h e western s t a t e s and as s e l e c tive herbicides i n carrots. Table

Year

II.

Chemicals

first

used

as

herbicides

Introduced

Chemical

1854 1855 1902 1906 1914 1923 1933 1940

Sodium c h l o r i d e Sulfuric acid Sodium a r s e n i t e Carbon disulfide Petroleum oils Sodium c h l o r a t e Dinitrophenol compounds Ammonium s u l f a m a t e



44


S o d i u m c h l o r a t e was f i r s t used i n France i n 1923. I t has been u s e d c h i e f l y as a s o i l s t e r i l a n t f o r c o n t r o l of d e e p - r o o t e d p e r e n n i a l weeds. Dinitrophenol was f i r s t u t i l i z e d i n F r a n c e i n 1933 f o r the control of a n n u a l b r o a d l e a f weeds i n c e r e a l s . I t has been e x t e n s i v e l y e m p l o y e d i n c e r e a l s , l e g u m e s , and f l a x i n the n o r t h e r n United S t a t e s . Ammonium s u l f a m a t e has b e e n u s e d f o r t h e control of woody p l a n t s s i n c e 1940. These o l d e r compounds each r e p r e s e n t e d attempts at weed c o n t r o l , s o m e t i m e s s e l e c t i v e weed control, through chemicals. T h e l a s t 30 y e a r s h a s b e e n a t i m e of r a p i d d e v e l o p m e n t o f new herbicides, mainly organic chemicals, i n the United S t a t e s . O v e r 40 b a s i c a n d specialty chemical manufacturers (such as pharmaceuti cal, o i l , r u b b e r , and p a i n t c o m p a n i e s ) h a v e partici p a t e d i n t h i s c h e m i c a l r e v o l u t i o n of weed control. M o r e t h a n 130 d i f f e r e n t o r g a n i c c h e m i c a l s a r e c u r r e n t l y e m p l o y e d a s h e r b i c i d e s i n t h e U.S. A l l of the main f a m i l i e s of o r g a n i c compounds a r e r e p r e s e n t e d : aro m a t i c , a l i p h a t i c , and h e t e r o c y c l i c . Herbicidal a c t i v i t y i s found i n a v a r i e t y of c l a s s e s of compounds: h a l o a l i p h a t i c , p h e n o x y , and b e n z o i c a c i d s ; carbamates; d i n i t r o a n i l i n e s ; a c e t a n i l i d e s ; amino triazines; q u a t e r n a r y p y r i d i n i u m s a l t s ; u r a c i l s ; and u r e a s . A few s e l e c t e d key e x a m p l e s a r e r e v i e w e d below. 2,4-D, i n t r o d u c e d by Amchem i n 1 9 4 5 , was the f i r s t of a s e r i e s of p h e n o x y a c e t i c a c i d h e r b i c i d e s (Fig. 3). These compounds a r e h i g h l y effective h e r b i c i d e s t h a t s e l e c t i v e l y k i l l b r o a d l e a f weeds w i t h l i t t l e o r no damage t o g r a s s e s . They a r e s t i l l widely used to c o n t r o l b r o a d l e a f weeds i n c o r n , wheat, b a r l e y , sorghum, sugarcane, g r a s s p a s t u r e s , and i n turf. Dalapon, a c h l o r i n a t e d a l i p h a t i c a c i d , was intro d u c e d b y Dow C h e m i c a l i n 1953 (Fig. 3). I t i s a grass k i l l e r , c o n t r o l l i n g tough p e r e n n i a l grasses such as j o h n s o n g r a s s , b e r m u d a g r a s s , and q u a c k g r a s s . It p o s s e s s e s a l m o s t no c r o p selectivity. D i u r o n was i n t r o d u c e d by du P o n t i n 1954 (Fig. 3). I t i s one o f a s e r i e s o f s u b s t i t u t e d u r e a herbicides. Diuron i s a p p l i e d preemergence to crops such as c o t t o n , a l f a l f a , g r a p e s , f r u i t and nut c r o p s . Foliar a c t i v i t y i s e n h a n c e d when a s u r f a c t a n t i s added t o the spray. EPTC was i n t r o d u c e d by S t a u f f e r i n 1959 (Fig. 3). I t i s a t h i o c a r b a m a t e and an i m p o r t a n t member o f a l a r g e f a m i l y of h e r b i c i d e s . Thiocarbamates are usually soil incorporated. EPTC i s u s e d i n c r o p s such


ALDER ET AL.

American

Herbicide

Industry

Dalapon 2,4-D

CH3-CCI2-COOH (Dow. 1953)

CI-^~~^0-CH -COOH 2

Cl

EPTC

(Amchem. 1945)

H C-H C-H C\ ïï ^N-C-S-CH -CH H C-H C-H c/ 3

2

3

2

2

2


Diuron

3

2

(Stauffer. 1959)

Cl

Atrazine {OuPonl, 1954)

ci Ν

DSMA

HC H C3

:CH-NH

CH -Às(0Na) 3

NH-CH -CH 2

Ν

3

0

Ν

(Geigy. 1958)

2

(Ansul. 1956)

Paraquat

Chloramben

2+ N-CH

H C-N

ci

3

3

^~~^-C00H NH Cl

3

(ICI. 1965)

2

(Amchem. 1958)

Linuron

V N H - C - N 0CH3 CI (Hoechst. 1960)

Figure 3. Selected U.S. herbicides introduced into agriculturecompany and year of introduction for each in parentheses


2X-


46


as a l f a l f a , c e r t a i n b e a n s , p o t a t o e s , a n d s w e e t potatoes. I n a d d i t i o n t o c o n t r o l l i n g numerous grass and b r o a d l e a f w e e d s , i t ' c o n t r o l s n u t s e d g e , one o f t h e world's worst weeds. DSMA w a s i n t r o d u c e d b y A n s u l i n 1 9 5 6 ( F i g . 3 ) . DSMA i s a n o r g a n i c a r s e n i c a l h a v i n g c o n t a c t , p o s t emergence a c t i v i t y . I t was f i r s t u t i l i z e d f o r c r a b grass control i n turf. I t i s an e f f e c t i v e h e r b i c i d e i n c o t t o n and i n c i t r u s t r e e s , b u t must be used as a d i r e c t e d spray to avoid contact with the crop foliage. A t r a z i n e was i n t r o d u c e d by G e i g y i n 1958 ( F i g . 3 ) . I t i s a member o f a l a r g e g r o u p o f s y m m e t r i c a l triazine herbicides. A t r a z i n e i s a preemergence h e r b i c i d e to w h i c h c o r n i s t o l e r a n t . I t i s t h e number one h e r b i c i d e i n acreage t r e a t e d and i n d o l l a r s of s a l e s in the United States. The compound i s a l s o used i n o r c h a r d s , p i n e a p p l e , sorghum, and sugarcane. Chloramben, a benzoic acid d e r i v a t i v e introduced by Amchem i n 1 9 5 8 , i s a s e l e c t i v e p r e e m e r g e n c e h e r b i cide ( F i g . 3 ) . I t i s used p r i n c i p a l l y i n soybeans, corn, and peanuts. Paraquat, a b i p y r i d y l q u a t e r n a r y ammonium s a l t , was i n t r o d u c e d by I C I i n 1965 ( F i g . 3 ) . I t i s a non s e l e c t i v e , c o n t a c t h e r b i c i d e on p l a n t f o l i a g e , b u t i s immediately i n a c t i v a t e d when a p p l i e d t o s o i l . I t i s used i n minimum t i l l a g e programs and as a p o s t e m e r gence d i r e c t e d spray i n sugarcane and i n f r u i t tree crops. L i n u r o n , a s u b s t i t u t e d urea i n t r o d u c e d by Hoechst in 1960, i s employed p r i m a r i l y as a preemergence h e r b i c i d e ; b u t i ta l s o h a s c o n t a c t e f f e c t on f o l i a g e (Fig. 3 ) . Linuron i s used p r i n c i p a l l y i n soybeans, c o r n , sorghum, wheat, and p o t a t o e s . I t i s often m i x e d w i t h o t h e r h e r b i c i d e s t o b r o a d e n t h e weed spectrum. B r o m a c i l i s a u r a c i l h e r b i c i d e i n t r o d u c e d by du P o n t i n 1 9 6 3 ( F i g . 4 ) . I t c o n t r o l s a b r o a d s p e c t r u m o f weeds i n c i t r u s and p i n e a p p l e c r o p s . The chemical i s a l s o used f o rgeneral v e g e t a t i o n c o n t r o l on n o n c r o p a r e a s s u c h a s r a i l r o a d s a n d i n d u s t r i a l areas. Picloram i s a picolinic acid derivative intro d u c e d b y Dow C h e m i c a l i n 1963 ( F i g . 4 ) . P i c l o r a m i s h i g h l y a c t i v e on most p e r e n n i a l b r o a d l e a f and woody s p e c i e s , and most g r a s s e s a r e r e s i s t a n t .


American

ALDER ET AL.

Herbicide

Industry

Picloram

Bromacil

NH

c=o

H C-C;

c

'y^t

C

,

v

3

I .N-ÇH-CH2-CH3 CH

2

c i

^ N

C

0

0

H

(Dow. 1963)

3

(DuPont. 1963)

Fluometuron


Trifluralin H C-H2C-H2Cv /CH2-CH2-CH 3

N

3

CH CF

3

3

(CIBA. 1964)

CF

3

(Lilly. 1963)

Bentazon Alachlor 0

CH2-CH3

CrVO-Cr^

\==/ CH2-CH3

(BASF, 1973)

(Monsanto. 1969)

Glyphosate

Metribuzin SCH

3

HOOC-CH2-NH-CH2- P(0H)

2

N-NH2

H C—C—CH 3

CH

(Monsanto, 1974)

3

3

(Bayer. 1971)

Figure 4. Selected U.S. herbicides introduced into agriculturecompany and year of introduction for each in parentheses

American Chemical Society Library

1155 16th St. N. w. Plimmer et al.; Pesticide Chemistry in the 20th Century

ACS Symposium Series; American Chemical Society: Washington, DC, 1977. Washington, D. C. 20031


48

PESTICIDE CHEMISTRY IN THE

20TH CENTURY

T r i f l u r a l i n i s a d i n i t r o a n i l i n e and was intro d u c e d by E l i L i l l y i n 1963 (Fig. 4). I t was the f i r s t of a number of s i m i l a r d i n i t r o a n i l i n e s . It is widely u s e d i n c o t t o n and s o y b e a n s and is labeled for u s e o n m o r e t h a n 50 c r o p s . It is usually incorporated i n t o the s o i l p r i o r to p l a n t i n g the crop. Fluometuron i s another substituted urea intro d u c e d by C I B A i n 1964 (Fig. 4). I t i s a preemergence h e r b i c i d e and finds i t s niche primarily in cotton and sugarcane. It i s usually applied in combination with o t h e r h e r b i c i d e s to b r o a d e n t h e s p e c t r u m of weed species controlled. A l a c h l o r i s an a c e t a n i l i d e i n t r o d u c e d by Monsanto i n 1969 (Fig. 4). Al,achlor i s a preemergence h e r b i c i d e , e x t e n s i v e l y used p r i m a r i l y i n corn, soybeans, and peanuts. Bentazon i s a benzothiadiazine introduced by BASF i n 1973 (Fig. 4). It i s a contact herbicide for s e l e c t i v e p o s t e m e r g e n c e c o n t r o l o f many broadleaf weeds i n s o y b e a n s , r i c e , c o r n , and peanuts. Metribuzin i s an a s y m m e t r i c a l t r i a z i n e intro d u c e d by B a y e r i n 1971 (Fig. 4). Metribuzin i s used a l o n e or i n c o m b i n a t i o n w i t h o t h e r h e r b i c i d e s i n soy b e a n s , s u g a r c a n e , and potatoes. Glyphosate i s a substituted glycine introduced by M o n s a n t o i n 1974 (Fig. 4). It is nonselective and when a p p l i e d t o p l a n t f o l i a g e , c o n t r o l s b o t h a n n u a l and p e r e n n i a l b r o a d l e a v e d weeds and grasses. The United S t a t e s has been a l e a d e r i n the d e v e l o p m e n t and use of h e r b i c i d e s . In 1951, herbi c i d e s a m o u n t e d t o o n l y 1 0 % o f t h e t o t a l o f 463 million pounds of p e s t i c i d e s p r o d u c e d i n t h i s c o u n t r y ( F i g . 5 ) . I n 1974, the l a t e s t year f o r which r e c o r d s are avail a b l e , 604 m i l l i o n p o u n d s , o r 4 3 % o f t h e 1,417 million pounds of p e s t i c i d e s p r o d u c e d i n the U n i t e d States, were h e r b i c i d e s (_5) . Moving to p e s t i c i d e s a l e s , i n m i l l i o n s of d o l l a r s at the manufacturer's l e v e l , there i s even greater growth ( F i g . 6). Herbicides have c o n s i s t e n t l y been more v a l u a b l e per pound than most o t h e r p e s t i c i d e s (5.). In 1951, herbicides c o n s t i t u t e d 13% of the d o l l a r s s p e n t f o r p e s t i c i d e s and i n 1974 herbicide s a l e s had grown t o 58%. I n 23 y e a r s h e r b i c i d e sales d o l l a r s had grown n e a r l y f i f t y f o l d , to over one b i l l i o n d o l l a r s per year. The leadership o f t h e U.S. herbicide industry is e v i d e n c e d by t h e f a c t t h a t , i n 1974, o v e r 58% of the worldwide expenditures f o r h e r b i c i d e s were i n the U.S. (6).


ALDER ET AL.

American

Herbicide

Industry


3.


49


50


F i g u r e 7 s h o w s t h e t o t a l a c r e s o f U.S. cropland and t h o s e t r e a t e d w i t h h e r b i c i d e s . Those acres planted to crops (not to pastures, f o r e s t s , etc.) i n 1959 w e r e 359 m i l l i o n a c r e s , a n d i n 1 9 7 4 , 368 m i l l i o n acres. The a c r e s t r e a t e d w i t h h e r b i c i d e s h a v e i n c r e a s e d f r o m 53 m i l l i o n i n 1 9 5 9 t o a n e s t i m a t e d 185 m i l l i o n i n 1974, or from l e s s than 15% of t h e a c r e s p l a n t e d i n 1 9 5 9 t o o v e r 5 0 % i n 1 9 7 4 (7_, 8, 9, 10). There has been r a p i d growth i n usage of p r e e m e r g e n c e h e r b i c i d e s ( F i g . 8 ) (JB, 9^, 10). Pre emergence h e r b i c i d e s a r e a p p l i e d t o the s o i l prior to g e r m i n a t i o n of weeds and c r o p s . Postemergence a p p l i c a t i o n s are a p p l i e d t o e s t a b l i s h e d weeds, such a s t h e u s e o f 2,4-D on w e e d s g r o w i n g i n c o r n o r w h e a t . I n 1959, most h e r b i c i d e a p p l i c a t i o n s were postemergence. P r e e m e r g e n c e t r e a t m e n t s have grown rapidly since that time. I n 1968, o n l y 45% of the h e r b i c i d e t r e a t m e n t s were p r e e m e r g e n c e ; b u t by 1 9 7 1 , 68%; and i n 1974, 70% of t h e a c r e s t r e a t e d w i t h h e r b i c i d e s employed preemergence treatments. H o w e v e r , some o f the newer postemergence m a t e r i a l s b e i n g developed f o r t h e c o n t r o l o f t o l e r a n t a n d r e s i s t a n t w e e d s may slow t h i s t r e n d , on a p e r c e n t a g e b a s i s , toward preemergence t r e a t m e n t s. The c h e m i c a l i n d u s t r y h a s s u p p o r t e d h e r b i c i d e r e s e a r c h i n t e r m s of b o t h s c i e n t i s t s and r e s o u r c e s . E s t i m a t e s of the numbers of h e r b i c i d e r e s e a r c h workers i n i n d u s t r y i n the United States adapted from i n f o r m a t i o n p r o v i d e d i n t h e l a s t two s u r v e y s o f t h e National A g r i c u l t u r a l Chemicals Association are pre s e n t e d i n F i g u r e 9 ( J L l , 1_2) . In 1971, t h e r e were 827 i n d u s t r y s c i e n t i s t s i n h e r b i c i d e r e s e a r c h a n d d e v e l o p m e n t — 3 1 9 P h . D . ' s , 183 M . S . ' s , a n d 325 B . S . ' s . S u p p o r t i n g t h e s e s c i e n t i s t s w e r e 495 o t h e r people s e r v i n g p r i m a r i l y as t e c h n i c i a n s . The n u m b e r s have c o n t i n u e d t o i n c r e a s e u n t i l i n 1975, t h e r e were 451 P h . D . ' s , 247 M a s t e r s , 404 B a c h e l o r s , w i t h 877 i n t h e " o t h e r " c a t e g o r y , f o r a t o t a l o f n e a r l y 2,000 people working i n industry h e r b i c i d e research i n the United States. We w o u l d f u r t h e r e s t i m a t e t h a t o f t h i s number a t l e a s t h a l f a r e c h e m i s t s - - o r g a n i c , physical, a n a l y t i c a l , and b i o c h e m i s t s . The r e m a i n i n g h a l f a r e b i o l o g i s t s and s c i e n t i s t s w i t h v a r i o u s agricultural backgrounds. F i g u r e 10 s h o w s e s t i m a t e s o f t h e e x p e n d i t u r e s by U.S. i n d u s t r y on r e s e a r c h and d e v e l o p m e n t o f h e r b i c i d e s ( J J _ , 12). I n 1971, 46. 3 m i l l i o n d o l l a r s was spent. I n f o u r y e a r s e x p e n d i t u r e s had i n c r e a s e d 80% to 83.3 m i l l i o n dollars.


3.

ALDER ET AL.

American

Herbicide

I

51

Industry

I U.S. CROPLAND ACREAGE

• i

'59

HERBICIDE TREATED ACRES

62

'65

'68

71

74


YEAR Figure 7.

Herbicide usage on U.S. croplands

Figure 8.

Figure 9.

Herbicide-treated acres

Herbicide research workers in industry (estimated)




Figure 11.

Projected U.S. herbicide market by product groups


3.

American

ALDER E T A L .

Herbicide

53

Industry

W h a t d o we s e e i n t h e n e a r f u t u r e f o r h e r b i c i d e s ? L o o k i n g a h e a d f i v e g r o w i n g s e a s o n s t o 1 9 8 0 , we s e e p r e d i c t i o n s of continued growth i n h e r b i c i d e sales and i n r e s e a r c h and d e v e l o p m e n t .


The

TrCLKm Ck&msLcalA

publication

recently

projected

growth o f t h e h e r b i c i d e market by p r o d u c t group (6) ( F i g . 1 1 ) . I n 1 9 7 4 , t h e f i r s t c o l u m n , we f i n d a r s e n i c a l s w i t h 1% o f t h e m a r k e t ; p h e n o x i e s w i t h 4 . 7 % ; p h e n y l u r e a s such as d i u r o n , l i n u r o n , and f l u o m e t u r o n w i t h 6.6%; b e n z o i c s s u c h a s c h l o r a m b e n , d i c a m b a , t r i c h l o r o b e n z o i c a c i d w i t h 9.5%; c a r b a m a t e s s u c h as EPTC, d i a l l a t e , and chloropropham w i t h 10.2%; and t h e t r i a z i n e s such as a t r a z i n e , prometryne, and cyanazine w i t h 29.7%. The " o t h e r s " c a t e g o r y w i t h 3 8 . 3 % i n c l u d e s a l a c h l o r , p a r a q u a t , t r i f l u r a l i n , a n d some o f t h e m o r e recent product e n t r i e s such as bentazon, g l y p h o s a t e , and m e t r i b u z i n . The s e c o n d c o l u m n d e p i c t s t h e 1 9 8 0 h e r b i c i d e market as compared w i t h 1974, w i t h a 44% growth i n crease overall. A l l p r o d u c t g r o u p s show some real growth, even though p e r c e n t o f t h e t o t a l market d e clines i n a l l e x c e p t t h e " o t h e r s " c a t e g o r y . The " o t h e r s " c a t e g o r y w i l l show a n a c t u a l i n c r e a s e o f 7 2 % and i n c r e a s e i t s p e r c e n t a g e s h a r e o f t h e m a r k e t from 38.3 i n 1 9 7 4 t o 4 5 . 8 % i n 1 9 8 0 . If r e s e a r c h and development expenses and i n d u s t r y s t a f f i n g c o n t i n u e t o grow a t t h e r a t e o f t h e l a s t five years, the expenditures f o r industry herbicide r e s e a r c h and development can be p r o j e c t e d t o double from 1975 t o 1980, r e a c h i n g 173 m i l l i o n d o l l a r s i n 1980 (Table I I I ) . I f i n d u s t r y p e r s o n n e l needs con t i n u e t o i n c r e a s e d u r i n g t h e next f i v e y e a r s a tt h e same r a t e a s i n t h e p a s t f i v e , t h e r e w i l l b e 1 , 5 0 0 s c i e n t i f i c a n d 1,800 s u p p o r t p e r s o n n e l r e q u i r e d b y i n d u s t r y i n 1980, o r an i n c r e a s e o f67%. Table

I I I .

Herbicide

1975 $83,300

R & D

projections

EXPENDITURES (000 s) f

1980 $173,500

PERSONNEL

1,102 877

SCIENTIFIC SUPPORT

1,500 1,800

1,979

TOTAL

3,300


54

PESTICIDE

C H E M I S T R Y IN T H E 20TH C E N T U R Y


W i t h a l l t h e w o r k t h a t h a s g o n e o n t h e l a s t 30 y e a r s , and w i t h o v e r 130 h e r b i c i d e s i n u s e t o d a y , a r e a l l t h e weed p r o b l e m s s o l v e d ? Not at a l l . Old p r o b l e m s a b o u n d a n d new p r o b l e m s a r i s e e a c h year. T h e r e a r e many o p p o r t u n i t i e s f o r new d e v e l o p m e n t s i n h e r b i c i d a l weed c o n t r o l . Some a r e : 1.

Further development of h e r b i c i d e s with true p h y s i o l o g i c a l tolerance t o s p e c i f i c crop plants s u c h as i s e x h i b i t e d by a t r a z i n e on c o r n .

2.

B e t t e r combinations of h e r b i c i d e s a r e needed t o p r o v i d e t h e b r o a d s p e c t r u m o f weed c o n t r o l n e e d e d in different localities.

3.

The c o n t r o l o f p e r s i s t e n c e needs f u r t h e r c o n sideration. A t t i m e s o n l y two o r t h r e e h o u r s o r two o r t h r e e d a y s o f h e r b i c i d e a c t i v i t y a r e desired. F o r many c r o p s a p e r s i s t e n c e o f t w o or t h r e e months i s needed; whereas i n c e r t a i n c o n d i t i o n s , as f o r s o i l s t e r i l a n t s and v a r i o u s t r e e c r o p s , two o r t h r e e y e a r s o f p e r s i s t e n c e may b e d e s i r e d . Through inherent compound c h a r a c t e r i s t i c s , t h r o u g h t h e amount a p p l i e d , a n d t h r o u g h i m p r o v e d f o r m u l a t i o n s , we c a n a n d must t a i l o r p e r s i s t e n c e o f h e r b i c i d e s t o f i t t h e p e r i o d o f weed c o n t r o l d e s i r e d .

4.

New a n d b e t t e r a q u a t i c h e r b i c i d e s , i n c l u d i n g a q u a t i c weed g r o w t h r e g u l a t o r s , a r e needed since a q u a t i c weeds a r e n o t w e l l c o n t r o l l e d a t p r e s e n t . We m u s t l e a r n h o w t o c o n t r o l w e e d s i n r u n n i n g water and i n waterways, as w e l l as l a k e s and ponds.

5.

The t r a n s f o r m a t i o n o f v a l u e l e s s b r u s h l a n d s t o productive pasture lands by t h e use of h e r b i c i d e s holds tremendous p o t e n t i a l f o r increased beef product ion.

6.

The u s e o f a n t i d o t e c h e m i c a l s or " a n t i - h e r b i c i d e s " on c r o p s t o c o u n t e r a c t the effect of herbicides and t h e r e b y increase crop tolerance i s a h i g h l y promising procedure. This technique i s already b e i n g u s e d i n o n e s e r i e s o f c o m p o u n d s a n d may e n j o y g r e a t e r a c c e p t a n c e as more " a n t i - h e r b i c i d e s " become a v a i l a b l e .

7.

D i f f e r e n c e s i n crop v a r i e t y t o l e r a n c e have been known f o r a l o n g t i m e . Thus, there e x i s t s t h e


3.

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p o s s i b i l i t y of developing, through s e l e c t i v e breeding, c r o p s t h a t a r e more r e s i s t a n t t o herbicides.


8.

The u s e o f growth r e g u l a t o r s t o s e v e r e l y inhibit w e e d s may p r o v e o f v a l u e . I n many c a s e s i t i s not r e a l l y n e c e s s a r y t o k i l l t h e weed. I t i s u s u a l l y adequate t o i n h i b i t i tso that i t i s unable t o compete s u c c e s s f u l l y o r t o reproduce.

The future of herbicides remains promising. New and b e t t e r compounds w i t h g r e a t e r s a f e t y t o c r o p s , t o man, and t h e e n v i r o n m e n t w i l l become a v a i l a b l e . I f the i n c r e a s e d food needs of t h e world a r e met, they w i l l be met a n d man's l a b o r b u r d e n e a s e d , i n p a r t , b y the u s e o f s u i t a b l e h e r b i c i d a l compounds.

Literature

Cited

1. 2. 3.

Hay, J. R. Weed S c i e n c e (1974) 22:439-442. Shaw, W. C. Weeds (1964) 12:153-162. Knake, E. L. and Slife, F. W. Weeds (1962) 10:26-29. 4. Timmons, F. L. Weed S c i e n c e (1970) 18:294-307. 5. U.S. Tariff Commission. S y n t h e t i c O r g a n i c C h e m i c a l s , U n i t e d S t a t e s P r o d u c t i o n and S a l e s of Pesticides and R e l a t e d P r o d u c t s , A n n u a l R e p o r t s for 1951-1974. 6. "World Pesticide M a r k e t s - - F C Special R e p o r t " Farm C h e m i c a l s (1975) 138(9):45-48. 7. "Agricultural Statistics" U.S.D.A., Editions 1959-1974. 8. " E x t e n t and Cost of Weed C o n t r o l w i t h H e r b i c i d e s and an E v a l u a t i o n of Important Weeds, 1965" Agr. R e s . S e r v i c e , U.S.D.A., Economic R e s . Service, Report ARS 3 4 - 1 0 2 , 1968. 9. " E x t e n t and Cost of Weed C o n t r o l w i t h H e r b i c i d e s and an E v a l u a t i o n of Important Weeds, 1968" Agr. R e s . S e r v i c e , U.S.D.A., Economic R e s . Service, Report A R S - H - 1 , 1972. 10. " F a r m e r s ' Use of Pesticides in 1971" U.S.D.A., Economic R e s . S e r v i c e , Agricultural Economic Report 252, 1974. 11. "Industry Profile S t u d y , 1973" N a t i o n a l Agricultural Chemicals Association, Washington, D.C. 12. "Industry Profile S t u d y , 1975" N a t i o n a l Agricultural Chemicals Association, Washington, D.C.


Pesticide Chemistry in the 20th Century - ACS Publications

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