Control of Cereal Diseases with Modern Fungicides in Western

7 Control of Cereal Diseases with Modern Fungicides in Western Europe

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on November 5, 2015 | http://pubs.acs.org Publication Date: April 22, 1986 | doi: 10.1021/bk-1986-0304.ch007

G. M . Hoffmann Faculty of Agriculture, Technical University Munich, D8050 Freising-Weihenstephan, Federal Republic of Germany

Economic and social changes in Western Europe in the past 35 years have caused farmers to alter farming practices in an attempt to achieve higher yields. These farmers have increased capital invest ments and decreased man-power hours needed for farming. This point is evidenced by a 50% reduction in the number of persons working in agricultural fields between 1970 and 1982 (Table I), as Western Europe entered the era of high intensity crop production(1). Table I.

Percentage of Population Employed in Agriculture.

Country Denmark France Germany FR Netherlands United Kingdom

1970 11.1 13.7 7.5 8.1 2.8

1982 6.4 7.9 3.5 4.9 1.9

This change in farming practices can also be observed by compar ing labor units per hectare of land used in agriculture. In the Federal Republic of Germany, labor units/ha were 29 in 1950 and only 7.9 in 1982. This reduction parallels an increase in combine har vested crops, especially winter cereals (wheat and barley). In Germany, the cropping area for winter wheat increased from 1.1 million hectares in the mid-1950's to 1.6 million hectares in 1980. Winter barley production increased from 127,000 hectares to 1.3 million hectares in 1982. This shift to a small grain monocul ture limited the possibilities for increasing crop rotation and increased the need for crop protection chemicals. Despite the added pest pressures from the lack of crop rotation, yields in Germany have increased by over 100% from 1952 to 1980 (Figure 1)(9). This in crease in yield is primarily due to the selection and growth of cereal varieties with a genetic potential for high yields (140 dt/ha). Other reasons for yield increase include: earlier s e e d i n g , 0097-6156/86/0304-0117$06.00/0 © 1986 American Chemical Society

In Fungicide Chemistry; Green, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.


FUNGICIDE CHEMISTRY

F i g u r e 1. Y i e l d i n c r e a s e i n wheat i n the F e d e r a l R e p u b l i c of Germany from 1952 t o 1980. (Reproduced w i t h p e r m i s s i o n from R e f . 9. C o p y r i g h t 1981 DLG V e r l a g F r a n k f u r t . )


7.

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119


h i g h e r p l a n t p o p u l a t i o n s / h a , h i g h e r m i n e r a l n u t r i t i o n , and t h e use o f growth r e g u l a t o r s t o reduce l o d g i n g . True y i e l d p o t e n t i a l s can o n l y be e x p r e s s e d when t h e c o n t r o l o f weeds, p a t h o g e n i c a g e n t s , and i n s e c t p e s t s a r e c o u p l e d w i t h p r o p e r cultivation, fertility, and o t h e r plant protection measures. An example o f these h i g h y i e l d s i n Western Europe appears i n T a b l e I I (1).

Table I I . Average Y i e l d o f Wheat and B a r l e y (dt/ha) i n Western Europe 1982. Country Denmark France Germany FR Netherlands U n i t e d Kingdom

Wheat 67.07 52.32 54.71 73.90 61.95

Barley 42.90 41.93 46.81 56.72 49.11

United States

23.96

30.84

T h i s system o f i n t e g r a t e d crop p r o d u c t i o n p l a c e s h i g h demands on a l l a s p e c t s o f crop p r o d u c t i o n , i n c l u d i n g t h e c o n t r o l l e d use o f p e s t i cides. Development and b e n e f i t from i n t e g r a t e d p e s t management systems depend upon t h e combined e f f o r t s o f t h e r e s e a r c h e r , d e v e l o p ment and s c o u t i n g persons and a h i g h l y t r a i n e d f a r m e r . Perhaps t h e most i m p o r t a n t r e s t r i c t i v e n e g a t i v e f a c t o r s i n c e r e a l p r o d u c t i o n i n Western Europe a r e t h e f u n g a l d i s e a s e s . E p i p h y t o t i c s o f s e v e r a l d i s e a s e s a r e a common o c c u r r e n c e . Other d i s e a s e s such as powdery mildew and glume b l o t c h o n l y o c c u r i n t h e more humid r e g i o n s . F u n g i c i d e s used f o r t h e c o n t r o l o f f o l i a r d i s e a s e s on wheat (Table I I I ) were p r i m a r i l y developed i n t h e l a s t decade. I n t h e p a s t 10 y e a r s , t r i a z o l e and amine d e r i v a t i v e s have p l a y e d a s i g n i f i c a n t role i n disease control i n cereals. These f u n g i c i d e s have g a i n e d w i d e - s p r e a d acceptance i n o n l y a few y e a r s because they a r e h i g h l y e f f i c a c i o u s and e c o l o g i c a l l y s a f e . The p o r t i o n o f c e r e a l c r o p p i n g a r e a s w h i c h have been sprayed w i t h f u n g i c i d e s w i t h i n t h e l a s t few y e a r s i s h a r d t o a s c e r t a i n . J e n k i n s and L e s c a r (3) e s t i m a t e d t h e f o l l o w i n g p e r c e n t a g e s f o r 1979: Denmark-23%, France-27%, N e t h e r l a n d s - 4 0 % , Germany (F.R.)-29%, and t h e U.K.-50%. An i n t e r n a t i o n a l s u r v e y on t h e u s e o f f u n g i c i d e s on c e r e a l s produced i n 1983 i s c o m p i l e d i n T a b l e I V . These f i g u r e s were c o n f i r m e d by P r i e s t l y and B a y l e s (8) f o r t h e U.K. In France and Germany, d i s e a s e c o n t r o l measures on c e r e a l s a r e d i r e c t e d p r i m a r i l y a g a i n s t f o o t r o t and l e a f d i s e a s e s , o r l e a f and ear d i s e a s e s . I n t h e U n i t e d Kingdom, t r e a t m e n t s a r e g e n e r a l l y made f o r t h e c o n t r o l o f l e a f d i s e a s e s , such a s powdery mildew. I t s h o u l d be mentioned t h a t these d a t a do n o t i n c l u d e t h e use o f t h e azole-compound t r i a d i m e n o l as a seed d r e s s i n g f o r e a r l y season p r o t e c t i o n a g a i n s t powdery mildew and r u s t f u n g i on wheat and b a r l e y .


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Table I I I .

Some S e r i o u s F u n g a l D i s e a s e s on C e r e a l s i n Western Europe and F u n g i c i d e s Used f o r C o n t r o l .

Crop Wheat

Fungicides Fenpropimorph, Triadimenol, Propiconazole Ortho-Difolatan, Propiconazole, Prochloraz Carbendazim, Thiophanate-methyl, Prochloraz Fenpropimorph, Triadimenol, Propiconazole, Prochloraz Propiconazole, Prochloraz Bitertanol, Triadimenol

Disease Powdery mildew


Glume b l o t c h

Eyespot

Barley

Powdery mildew

Net b l o t c h Typhula

blight

Table I V . F u n g i c i d e Treatment i n C e r e a l C r o p p i n g (x 1000 ha) Accumulated f o r D i s e a s e s i n Western Europe 1983.

Country Denmark France Netherlands U n i t e d Kingdom Germany FR

Foot Rot 201 1,575 20 1,180 534

Sum

3,510

Foot Rot and L e a f Diseases 33 4,435

-

485 1,392

6,345

Treatment A g a i n s t L e a f and Ear Leaf Diseases Diseases 1,757 279 4,880 141 2,400 565 1,387 1,098

-

4,197

Areas

Ear Diseases 14

-

-

218 1,420 249

8,589

1,901

F u n g i c i d e e f f e c t i v e n e s s i s based on t h e s e v e r i t y o f d i s e a s e p r e s s u r e , the s u s c e p t i b i l i t y o f t h e h o s t , t h e b i o l o g i c a l environment, the b i o l o g i c a l a c t i v i t y o f the compound and the time and number o f applications. I n Western Europe, l o s s e s i n c e r e a l y i e l d s range from 20 t o 30% (10-20 d t / h a ) . The average l o s s i n many t r i a l s due t o c e r e a l d i s e a s e l i e s between 5 and 12%. However, these l o s s e s can be reduced through the use o f f u n g i c i d e s . Survey d a t a from France (5) demonstrate t h e y e a r l y v a r i a t i o n s o f t h e e f f e c t s o f f u n g i c i d e t r e a t ments on w i n t e r wheat (Table V ) .


7.

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121


Table V. Mean Y i e l d I n c r e a s e s o f W i n t e r Wheat i n France a f t e r Use o f F u n g i c i d e s . Frequency o f Y i e l d I n c r e a s e >0.5 t / h a (%) 37 40 29 4 48 60 31


Yield

Increase (%) 7.3 8.2 6.5 2.0 9.2 10.8 6.4

Year 1973 1974 1975 1976 1977 1978 1979

The p e r c e n t i n c r e a s e i n y i e l d i s o f t e n r e l a t e d t o weather conditions. I n d r y y e a r s (1976) a r e l a t i v e l y s m a l l number o f f u n g i c i d e c e r e a l t r i a l s showed an i n c r e a s e i n y i e l d , b u t d u r i n g wet y e a r s (1978) 60% o f t h e t e s t s showed y i e l d i n c r e a s e s . I n long-term t r i a l s (4) i n t h e Western r e g i o n o f Germany, seed t r e a t m e n t s and f o l i a r a p p l i c a t i o n s o f t r i a z o l e f u n g i c i d e s reduced crop l o s s e s from powdery mildew up t o 25% (Table V I ) .

T a b l e V I . Long-term R e s u l t s o f Mildew C o n t r o l on W i n t e r Wheat 1975/76 t o 1980/81.

Site A

Β

Treatment No treatment

Grain Y i e l d A b s o l u t e (dt/ha) R e l a t i v e (%) 100 48

Baytan s p e c i a l (seed t r e a t m e n t )

56

118

Baytan s p e c i a l + Bayleton

60

125

No

53

100

Baytan s p e c i a l (seed t r e a t m e n t )

57.2

108

Baytan s p e c i a l + Bayleton

62.0

117

treatment

E f f i c a c y e v a l u a t i o n s (7) o f p l a n t p r o t e c t a n t compounds need t o be made i n v a r i o u s c r o p p i n g systems u s i n g v a r y i n g l e v e l s o f n i t r o g e n (Table V I I ) . C o n t r o l l i n g eyespot alone (PS^) i s inadequate. When combined w i t h t r e a t m e n t s a g a i n s t l e a f and e a r d i s e a s e s (PS^, P S ^ ) , y i e l d i n c r e a s e s o f up t o 12% have been o b s e r v e d . The a d d i t i o n a l use of organo-phosphorous i n s e c t i c i d e s (PS^) a g a i n s t aphids r e s u l t s i n further increases. There i s a 20.7% d i f f e r e n c e i n y i e l d between


FUNGICIDE CHEMISTRY

122

c r o p p i n g system IA and VC. on y i e l d , the q u a l i t y of improved.

I n a d d i t i o n t o the e f f e c t of f u n g i c i d e s g r a i n ( s p e c i f i c weight * k g / h i ) can be


Table V I I . D i f f e r e n t Types o f N - f e r t i l i z a t i o n , D i s e a s e C o n t r o l Measures and Y i e l d (dt/ha) of W i n t e r Wheat (29 T r i a l s 1980 - 1982)

Cropping System I II III IV V PS. PS PS PS, PS 2

3

» « «

Disease Control PS P S

P S P S

P S

2 3 4

5

A Abs. 69.3 70.8 72.6 77.7 70.9

Type o f N - N u t r i t i o n Β Rel. Rel. Abs. 100 100 71.0 72.8 102.5 102.6 104.7 105.2 74.4 11.6 112.6 70.3 81.6 114.9 115.7

C Abs. 71.5 73.2 75.0 79.5 83.3

Rel. 100 102.3 104.8 111.1 116.5

C y c o c e l (Growth r e g u l a t o r ) Cycocel + Cercobin F l Cycocel + Cercobin F l + Corbel Cycocel + Cercobin F l + Corbel + Ortho-Difolatan Cycocel + Cercobin Fl + Corbel + Ortho-Difolatan P a r a t h i o n POX

+

There i s no doubt t h a t use o f f u n g i c i d e s must be j u s t i f i e d on an e c o l o g i c a l and e c o n o m i c a l b a s i s . The farmer's d e c i s i o n t o use a f u n g i c i d e i s based on the r e s u l t s of many y e a r s o f l o c a l e x p e r i e n c e and the o c c u r r e n c e of s p e c i f i c d i s e a s e organisms o f economic impor tance i n the growing a r e a . On the o t h e r hand, i t i s the t a s k of p l a n t p a t h o l o g i s t and c o u n s e l i n g s e r v i c e s t o compile b a s i c knowledge on e p i d e m i o l o g y o f c e r t a i n pathogens and on the c a l c u l a t i o n of disease/loss rate. These e f f o r t s are combined t o p r o v i d e warning f o r e c a s t s t o the farmer. I n England, i t i s recommended t h a t f u n g i c i d a l treatment f o r c o n t r o l o f powdery mildew on s p r i n g b a r l e y be a p p l i e d when 3% o f the a r e a o f the two o l d e s t green l e a v e s i s i n f e s t e d w i t h mildew. For w i n t e r wheat i n the F e d e r a l R e p u b l i c of Germany, the t h r e s h o l d v a l u e i s about 1% i n f e s t e d a r e a o f the uppermost two l e a v e s o r an i n f e s t a t i o n f r e q u e n c y o f more than 60%, t h a t i s when about t w o - t h i r d s o f a l l p l a n t s show mildew a t t a c k . These v a l u e s are thought t o i n d i c a t e the presumable b e g i n n i n g of an epidemic development. Models f o r r i s k e s t i m a t i o n o f c e r e a l eyespot were developed w h i c h employ a g r e a t number of parameters ( p r e v i o u s c r o p , s o i l , w e a t h e r , c u l t i v a t i o n , sowing d a t e , p l a n t d e n s i t y , c u l t i v a r and v i g o r i n s p r i n g ) . R i s k models p r o v i d e a good o r i e n t a t i o n f o r the c o u n s e l i n g s e r v i c e s and can be a d j u s t e d t o l o c a l c o n d i t i o n s and e x p e r i e n c e s . An example o f a w e l l - d e v e l o p e d p r o g n o s t i c model on c e r e a l d i s e a s e s i s the c o o p e r a t i v e p r o j e c t EPIPRE ( F i g u r e 2 ) . The h e a r t o f EPIPRE i s a d a t a bank w h i c h c o n t a i n s the c o r e d a t a f o r each f i e l d and the v a r i a b l e d a t a p r o v i d e d by the farmers d u r i n g the season. EPIPRE can a l s o m o n i t o r r e c e n t weather d a t a . The computation procedures f o r r i s k



7. H O F F M A N N


farmers' basic data per field

123

epidemiological models databank

farmers' observations in field

synoptic weather data

recommendation to farmers

no treatment now, send new observation

do not t

F i g u r e 2. P r o g n o s t i c model on c e r e a l d i s e a s e s . (Reproduced w i t h p e r m i s s i o n from R e f . 10. C o p y r i g h t 1981 O r g a n i z a t i o n Européenne e t Méditerranéenne pour l a P r o t e c t i o n des P l a n t e s . )



124

FUNGICIDE CHEMISTRY

e s t i m a t i o n have been s t o r e d i n t h e model s e c t i o n . L i n k e d t o t h e epidemic growth model i s a complex d e c i s i o n network w i t h 27 d e c i s i o n points. The d e c i s i o n network uses a l l a v a i l a b l e e p i d e m i o l o g i c a l , agronomic and economic i n f o r m a t i o n . The number o f f i e l d s r e g i s t e r e d under t h i s program i n t h e N e t h e r l a n d s was about 1200 i n 1981 ( 1 0 ) . A l t h o u g h g e n e r a l l y s a t i s f a c t o r y f o r mildew and r u s t , d i s e a s e t h r e s h o l d s have n o t been adequate f o r eyespot and d i s e a s e s caused by S e p t o r i a , D r e c h s l e r a and Rhynchosporium. V a r i o u s p r o g n o s t i c models a r e under i n t e n s i v e i n v e s t i g a t i o n i n d i f f e r e n t i n s t i t u t i o n s . They have t o be compiled f o r every d i s e a s e and adapted t o r e g i o n a l c o n d i tions. F o r t h i s r e a s o n , no s i n g l e European model can be e x p e c t e d , s i n c e e c o l o g i c a l and e c o n o m i c a l p r e - r e q u i s i t e s between t h e v a r i o u s c o u n t r i e s and w i t h i n each c o u n t r y , as w e l l as between t h e v a r i o u s r e g i o n s , are too d i f f e r e n t . Numerous i m p o n d e r a b i l i t i e s , e s p e c i a l l y the l a c k o f a c c u r a t e weather p r o g n o s e s , f r e q u e n t l y r e s u l t i n r o u t i n e t r e a t m e n t s by t h e f a r m e r s . These f u n g i c i d e t r e a t m e n t s have been shown t o be e c o n o m i c a l l y j u s t i f i e d by t h e average o f many y e a r s , b u t not i n every s i n g l e y e a r . The use o f modern f u n g i c i d e s has a l s o t o be viewed under t h e a s p e c t o f t h e energy o u t p u t / i n p u t r a t i o . A g r i c u l t u r a l and f o r e s t economies a r e t h e o n l y economic a c t i v i t i e s w h i c h r e s u l t i n a n e t production. However, o n l y 0.5% o f t h e r a d i a n t energy r e a c h i n g t h e a g r i c u l t u r a l a r e a i n N o r t h w e s t e r n Europe i s used by p l a n t p r o d u c t i o n . Any improvement o f t h i s u t i l i z a t i o n r a t e s h o u l d have t h e h i g h e s t p r i o r i t y w i t h r e g a r d t o energy p o l i c i e s . I n t h e M i d d l e Ages ( w i t h a c e r e a l y i e l d o f about 8 dt/ha g r a i n + s t r a w ) , u t i l i z a t i o n r a t e was 0.25%. On t h e b a s i s o f contemporary c e r e a l y i e l d s i n Western Europe (50 dt/ha g r a i n + 40 dt/ha s t r a w ) , e n e r g e t i c e f f i c i e n c y o f s o l a r energy i s 1.5%; t h e o r e t i c a l l y t h i s c o u l d be r a i s e d t o 4%. Energy i n p u t p e r a r e a has i n c r e a s e d i n Western Europe's a g r i c u l t u r e by 500% i n t h e l a s t c e n t u r y . About 40% o f the t o t a l energy i n p u t i s used f o r f u e l s , 30% f o r f e r t i l i z e r s and about 1 - 2 % f o r p l a n t p r o t e c t i o n . Energy consumption f o r 1 kg o f a p l a n t p r o t e c t i o n agent i s compensated by a y i e l d i n c r e a s e o f 17.6 kg wheat ( 2 ) . E x p e r i e n c e has shown t h a t n o t o n l y energy i n p u t f o r c h e m i c a l p l a n t p r o t e c t i o n i n c e r e a l s c a n be compensated many times over by a r e d u c t i o n o f d i s e a s e l o s s e s , b u t t h a t w i t h a r e l a t i v e l y s m a l l consumption of f o s s i l f u e l used i n p r o d u c t i o n o f modern f u n g i c i d e s , t h e u t i l i z a t i o n o f s o l a r energy by p l a n t s i s c o n s i d e r a b l y i n c r e a s e d . I t has been argued t h a t l e s s i n t e n s i v e a g r i c u l t u r a l systems provide a b e t t e r output/input r a t i o . I n systems where t h e o n l y i n p u t i s human l a b o r , an o u t p u t / i n p u t r a t i o may be as h i g h as 30:1; b u t t h i s worker a l s o consumes food c o n t a i n i n g 4.4 G J / y e a r . I n t h e U n i t e d Kingdom, a worker and h i s f a m i l y use an energy l e v e l o f 130 GJ/year. Thus, i f t h e p r i m i t i v e a g r i c u l t u r a l system used such w o r k e r s , the o u t p u t / i n p u t r a t i o would be reduced t o 1:1 compared w i t h o v e r 2:1 f o r c e r e a l s i n Western Europe(6) T h e r e f o r e , t h e f i n a l g o a l can o n l y be t o improve t h e o u t p u t / i n p u t r a t i o by b e i n g v e r y energy e f f i c i e n t . T h i s can be a c c o m p l i s h e d by u s i n g p l a n t p r o t e c t i o n measures, such as modern f u n g i c i d e s , t o p r o t e c t t h e energy r a t i o a l r e a d y a c h i e v e d a g a i n s t l o s s e s by d i s e a s e s and o t h e r a g r i c u l t u r a l p e s t s .


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125


Literature Cited 1. FAO Production Yearbook 36, 1982. 2. Green, M.B. and T. F. West, 1977: Pesticides and energy. In: Chemicals for Crop Protection and Pest Control, Oxford, pp. 23 28. 3. Jenkins, J . E . E . , L. Lescar, 1980: Use of Foliar Fungicides on Cereals in Western Europe. Plant Disease 64, 987 - 994. 4. Kolbe, W. 1982: Weitere Versuche uber die fungizide Wirkung und den Ertragseinfluss von Baytan bei der Beizung im Getreidebau (1975 - 1981). Pflanzenschutz Nachr. Bayer 35, 72 - 103. 5. Lescar, L., 1980: Ou en est l a lutte contre les maladies? Perspect. Agricoles 33, 49 - 55. 6. Lewis, D.A., J.A. Tatchell, 1979: Energy i n UK Agriculture. J . Sci. Food agr. 30, 449 - 457. 7. Limburgerhof aktuell, 1984, BASF Aktiengesellschaft Landwirtschaftliche Versuchsstation Limburgerhof. 8. Priestley, R.H., R.A. Bayles, 1980: Factors Influencing Farmer' Choice of Cereal Varieties and the Use by Farmers of Varietal Diversification Schemes and Fungicides. J . Natu. Inst. Agr. Bot. 15, 215 - 230. 9. Reiner, L . et al., 1981: Weizen aktuell. DLG Verlag Frankfurt. 10. Zadoks, J . C . , 1981: EPIPRE: A Disease and Pest Management System for Winter Wheat Developed in the Netherlands. EPPO B u l l . 11, 365 - 369. RECEIVED January 24, 1986


Control of Cereal Diseases with Modern Fungicides in Western

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