GB2218907A - Combatting brown plant hopper eggs - Google Patents

Abstract

A method of combatting brown plant hopper eggs at a locus at which a crop is growing or is to grow comprises applying to the locus an amount of carbaryl effective to combat the eggs.

Description

"COMBATTING BROWN PLANT HOPPER EGGS" This invention relates to a new method of combatting eggs of the brown plant hopper (Nilaparvata lugens; hereinafter referred to as BPH) at a locus at which there is growing a crop, especially a plantation crop, more especially rice.

Many insecticides are well known as active ingredients to protect plants against insects.

A particular problem among those which farmers have to face is the destruction of rice by BPH. This problem is such an important one that in some countries many insecticides have been banned because they do not kill BPH. By not killing BPH, such insecticides enhance its development because other creatures are killed so that BPH are able to eat whatever they like, relatively free from competition and predation.

Carbaryl is a well known insecticide whose chemical name is l-naphthyl mehylcarbamate. Its formula is Ar-O-CO-NH-CH3 wherein Ar is alpha-naphthyl (see page 125, the Pesticide Manual, 1987 edition; published by the British Crop Protection Council).

Carbaryl is an insecticide which is most commonly effective against larvae and adults and generally less effective against eggs. Moreover, it is only weakly effective against BPH adults.

Most surprisingly, it has been found that carbaryl is very effective against the eggs of BPH.

The present invention provides a method of combatting BPH at a locus at which there is growing a crop, especially a plantation crop, more especially rice, which comprises applying to the locus an effective amount of carbaryl to combat BPH eggs.

By the term "eggs", as used in this specification, it is to be understood eggs which are in their simple state laid upon the soil or on the plant or eggs which are in the pregnant female BPH.

The invention enables BPH to be combatted at the egg stage before they reach the damaging later stages.

Thus, carbaryl is applied to the locus to be treated before substantial infestation with BPH larvae occurs.

For instance, on rice plants, one should apply the carbaryl against BPH eggs before one would first apply it against the first BPH stage (nymph stage), preferably 4 to 7 days before one would first apply it against the first BPH stage (nymph stage).

The carbaryl may be applied once or more than once. Thus, for some crops one may apply the carbaryl periodically through the insects season. Usualiy carbaryl is applied at a rate of 0.25 to 2kg/ha, preferably 0.5 to 1.5kg/ha.

The carbaryl is applied to a locus at which the crop is to grow or, preferably, is growing. Carbaryl may be used to combat BPH eggs with outstanding safety to the crop.

Generally the carbaryl may be applied in the form of a solid, e.g. dusts or granules, or, preferably, in the form of a liquid, e.g. an emulsifiable concentrate or wettable powder, which is diluted, generally with water, for application or a true solution. The ovicidal compositions may be prepared by admixing the ingredients. Generally they contain from 0.001 to 90% of carbaryl. A concentrate may contain for instance from 5 to 90% of carbaryl.

Parts and percentages in this specification are by weight unless otherwise indicated.

The composition may contain a surface active agent and/or a carrier. The carrier may be solid or liquid. The composition may contain a fertiliser. The carbaryl may be used in sequence or admixture, particularly admixtures with another pesticide e.g. an insecticide, acaricide or fungicide. In a preferred embodiment, however, carbaryl is the sole insecticide and in the form of a wettable powder, preferably a wettable powder known under the trade marks SEVIN 50W, SEVIN 80S, or SEVIN 85S.

The invention is illustrated by the following test example.

EXAMPL! A rice variety known as Pelita I/1 was used as the host plant. On each plant 7 pregnant BPH were introduced for 24 hours.

After this first day the plants were sprayed either with carbaryl, or with 2-sec-butylphenyl methylcarbamate, which is another commercial carbamate insecticide, otherwise known as BPMC or fenobucarb.

Observation was conducted on the nymphs produced. After there was no longer any production of nymphs, the plants were immersed in fuchsin solution (a biological stain) to facilitate the counting of the eggs hatched. Every treatment was repeated ten times.

The dosages of active ingredients used were similar to those normally used for insecticidal use.

The following results were found.

dosage of active unhatched ingredient in kg/ha eggs carbaryl 1.275 43.4 % BPMC 1.0 1 % Control 0 0.27 % (untreated plants)

Thus, surprisingly, carbaryl is remarkably superior to the closely related BPMC.

Claims (12)

1. A method of combatting brown plant hopper eggs at a locus at which a crop is growing or is to grow, which method comprises applying to the locus an amount of carbaryl effective to combat brown plant hopper eggs.

2. A method according to claim 1 wherein the carbaryl is applied before substantial infestation by brown plant hopper larvae occurs.

3. A method according to claim 1 or 2 wherein the carbaryl is applied 4 to 7 days before carbaryl would be applied against the first brown plant hopper (nymph) stage.

4. A method according to any one of the preceding claims wherein the crop is a plantation crop.

5. A method according to any one of the preceding claims wherein the crop is rice.

6. A method according to any one of the preceding claims wherein the carbaryl is applied by spraying a liquid carbaryl-containing composition.

7. A method according to claim 6 wherein the liquid composition is obtained from a wettable powder.

8. A method according to claim 7 wherein the wettable powder is SEVIN 50W, SEVIN 80S or SEVIN 858.

9. A method according to any one of the preceding claims wherein the carbaryl is applied at a rate of 0.25 to 2 kg/ha.

10. A method according to any one of the preceding claims wherein the carbaryl is applied at a rate of 0.5 to 1.5 kg/ha.

11. A method according to any one of the preceding claims wherein a crop is growing at the locus.

12. A method according to claim 1 substantially as described in the foregoing Example.