GB2168897A

GB2168897A - Process and composition for controlling eyespot in cereal crops

Info

Publication number: GB2168897A
Application number: GB08429037A
Authority: GB
Inventors: Stephen Waterhouse
Original assignee: BASF PLC
Current assignee: BASF PLC
Priority date: 1984-11-16
Filing date: 1984-11-16
Publication date: 1986-07-02
Also published as: GB8429037D0

Abstract

Eyespot in cereal crops that is resistant to benzimidazole fungicides can be controlled by the use of carbamate compounds selected from a) phenyl carbamates of the formula <IMAGE> where R is a hydrocarbon radical of up to 6 carbon atoms, optionally substituted by halogen and optionally unsaturated, and b) methyl carbamates of the formula <IMAGE> where R<1> denotes hydrogen or methyl, R<2> denotes hydrogen or alkyl of up to 6 carbon atoms, R<3> denotes hydrogen, acetyl or alkyl of up to 6 carbon atoms optionally substituted by halogen, methoxy, ethoxy, methylthio or ethylthio and R<4> denotes alkyl of up to 3 carbon atoms optionally substituted by halogen, or acetyl. The carbamate compound may be applied separately from or together with a benzimidazole fungicide for the control of eyespot in cereal crops such as wheat or barley.

Description

SPECIFICATION Process and composition for controlling eyespot in cereal crops The present invention relates to a process for the control of the fungal disease eyespot, caused by Pseudocercosporella herpotrichoides, in cereal crops, especially wheat and barley, and to a composition for use in that process.

It is known to use carbendazim and related benzimidazole fungicides, such as benomyl and thiophanatemethyl, for the control of eyespot in cereals, especially winter wheat, winter barley and winter rye. However, over the past two or three years strains of Pseudocercosporella herpotrichoides which are resistant to benzimidazole fungicides have been encountered more and more frequently. It is therefore an object of the present invention to provide a process and composition having an improved effect against P. herpotrichoides strains resistant to benzimidazole fungicides alone.

Cloethocarb(2-(1 -methoxy-2-chloro)-ethoxy-phenyl-N-methyl carbamate) is a known insecticide, and chlorpropham, barban and chlorbufam are known herbicides for the control of various weeds in crops, including cereal crops. However, these compounds have not previously been suggested for commercial use as fungicides for P. herpotrichoides and they are thought to be inactive against P. herpotrichoides strains which are sensitive to benzimidazole fungicides.

Surprisingly, chloethocarb, chlorpropham, chlorbufam and barban have now been found to have a significant effect against P. herpotrichoides strains which are resistant to benzimidazole fungicides, a phenomenon which is known as negative cross-resistance. Accordingly, improved control of eyespot can be achieved by combined use of a benzimidazole fungicide and certain carbamate compounds.

According to the present invention a process for controlling eyespot in cereal crops caused by a Pseudocercosporella herpotrichoides strain resistant to benzimidazole fungicides comprises applying to the crop a carbamate compound selected from a) phenyl carbamates of the formula

where R is a hydrocarbon radical of up to 6 carbon atoms, optionally substituted by halogen and optionally unsaturated, b) methyl carbamates of the formula

where R' denotes hydrogen or methyl, R2 denotes hydrogen or alkyl of up to 6 carbon atoms, R3 denotes hydrogen, acetyl or alkyl of up to 6 carbon atoms optionally substitued by halogen, methoxy, ethoxy, methylthio or ethylthio and R4 denotes alkyl of up to 3 carbon atoms optionally substituted by halogen, or acetyl.

The invention also includes a process for combating eyespot in cereals comprising applying to the crop together or separately (i) a benzimidazole fungicide, and (ii) a compound selected from (a) and (b) as defined above.

Thirdly the invention provides a composition for combating eyespot in cereals comprising (i) a benzimidazole fungicide, and (ii) a compound selected from (a) and (b) as defined above.

Amongst the phenyl carbamates (a) of the formula I R preferably has 3 or 4 carbon atoms, is saturated or contains acetylenic unsaturation and is unsubstituted or monosubstituted by chlorine. Chlorpropham (R = isopropyl), barban (R = 4-chlorobut-2-yn-1-yl) and chlorbufam (R = but-1-yn-3-yl) are particularly preferred.

Amongst the methyl carbamates (b) R2 preferably denotes hydrogen, methly or ethyl, R3 preferably denotes hydrogen, acetyl, methyl, ethyl, chloromethyl or chloroethyl and R4 preferably denotes methyl, ethyl, chloroethyl. Cloethocarb (R1 = R2 = hydrogen, R3 = chloromethyl and R4 = methyl) is particularly preferred.

Amongst the benzimidazole fungicides carbendazim is preferred but benomyl, thiophanate and thiophanatemethyl can also be used.

The methyl carbamates may be used on both barley and wheat in amounts up to 2.5 kg/hectare, preferably in amounts of 0.1 to 2.5 kg/hectare. The phenyl carbamates may be used on wheat in amounts up to 2.5 kg/hectare but care should be taken when applying them to barley that the damage to the barley does not outweightthe benefits of added control of eyespot. Forthis reason chlorpropham and chlorbufam are not recommended for commercial use on barley. The benzimidazole fungicides may be used in conventional amounts, for example O.'1 to 1 kglhectare.

The carbamate compounds (a) and (b) are applied to the crop post-emergence, preferably at or before growth stages 30-31, but successful results can also be obtained by later spraying, for example at stages 32-37.

The compositions according to the invention may be used as solutions, emulsions, suspensions or dusts in conjunction with appropriate carriers or diluents, for example water, organic solvents, wetting, emulsifying and dispersing agents etc. Details of formulations appear for example in UK Patents 1190614 and 1426233.

The effectiveness of procedures according to the invention is illustrated by the following Examples.

Example 7 Plots of winter barley were sprayed at growth stages 32-37 with carbendazim alone and in conjunction with cloethocarb, chlorpropham, chlorbufam and barban. The results are shown in Table 1.

Treatment Concentration Crop % Tillers % Yield Active of active damage with mod + Control dt/ha ingredient ingredient after severe g/hectare 47 days eyespot 0-10 scale Untreated - 0 60 - 85.54 carbendazim 250 0 49 19 85.54 carbendazim + 250 + 480 0.1 40 33 82.72 cloethocarb 250 + 2400 0 31 49 83.80 carbendazim + 250 + 500 2.2 39 35 75.43 chlorpropham 250 + 1000 4.6 48 20 58.80 carbendazim + 250 + 500 0.6 51 15 79.46 chlorbufam* " "* 250 + 1000 1.2 35 42 73.26 carbendazim + 250 + 312 0 31 49 87.06 barban *The chlorbufam mixture also contained 1240 chloridazon per 100 g chlorbufam but this is not considered to have affected the crop or the fungus.

Example 2 Plots of winter wheat were sprayed at growth stage 31 with carbendazim or at growth stage 32 with cloethocarb. The results are shown in Table 2.

Treatment Concentration %tillers % Yield Active of active with mod control dtlha Ingredient ingredient + severe glhectare eyespot Untreated - 77 - t 51.57 carbendazim 250 61 21 53.48 cloethocarb 2400 47 39 47.14 The results of Examples 1 and 2 show that cloethocarb gives a marked reduction of eyespot infection as compared to carbendazim alone whether it is used with or without carbendazim. Although chlorpropham and chlorbufam gave reductions of eyespot infection they caused damage to the barley.

Claims

1. A process for controlling eyespot in cereal crops caused by a Pseudocercosporella herpotrichoides strain resistant to benzimidazole fungicides which comprises applying to the crop a carbamate compound selected from b) methyl carbamates of the formula

where R1 denotes hydrogen or methyl, R2 denotes hydrogen or alkyl of up to 6 carbon atoms, R3 denotes hydrogen, acetyl or alkyl of up to 6 carbon atoms optionally substituted by halogen, methoxy, ethoxy, methylthio or ethylthio and R4 denotes alkyl of up to 3 carbon atoms optionally substituted by halogen, or acetyl, and a) phenyl carbamates of the formula

where R is a hydrocarbon radical of up to 6 carbon atoms, optionally substituted by halogen and optionally unsaturated.

2. A process for combating eyespot in cereals comprising applying to the crop together or separately (i) a benzimidazole fungicide, and (ii) a carbamate compound selected from (b) and (a) as defined in claim 1.

3. A process as claimed in claim 1 or 2, wherein a methyl carbamate of the formula II in which R2 denotes hydrogen, methyl or ethyl, R3 denotes hydrogen, acetyl, methyl, ethyl, chloromethyl or chloroethyl, and R4 denotes methyl, ethyl or chloroethyl is used as the carbamate compound.

4. A process as claimed in claim 1 or 2, wherein the carbamate compound is cloethocarb.

5. A process as claimed in claim 3 or 4, wherein the cereal is wheat or barley and the carbamate compound is applied in an amount of 0.1 to 2.5 kg/hectare.

6. A process as claimed in claim 1 or 2, wherein a phenyl carbamate of the formula I in which R has 3 or 4 carbon atoms, is saturated or contains acetylenic unsaturation and is unsaturated or monosubstituted by chlorine is used as the carbamate compound and the cereal is wheat.

7. A process as claimed in claim 1 or 2, wherein the carbamate compound is chlorpropham or chlorbufam and the cereal is wheat.

8. A process as claimed in any of claims 1 to 7, wherein the benzimidazole fungicide is carbendazim.

9. A process as claimed in any of claims 1 to 8, wherein the carbamate compound is applied post-emergence but at or before growth stage 31.

10. A process as claimed in claim 1 or 2, carried out substantially as hereinbefore described.

11. A composition for combating eyespot in cereals comprising (i) a benzimidazole fungicide, and (ii) a carbamate compound selected from (b) and (a) defined in claim 1.

12. A composition as claimed in claim 11, wherein the carbamate compound is as defined in any of claims 3 to 7.

13. A composition for combating eyespot in cereals comprising carbendazim and cloethocarb.