Studies on the insecticidal properties of benfuracarb against the brown rice planthopper, Nilaparvata lugens (Stal)(Hemiptera: Delphacidae)

The insecticidal properties of the carbamate insecticide benfuracarb against the brown rice planthopper, Nilaparvata lugens, were investigated by different methods of its application, i.e., topical, foliage, plant-base drench or granular application, Parafilm test method, and root dipping method. Benfuracarb, a sulfenylated derivative of carbofuran, exhibited relatively poor insecticidal activity against the brown rice planthopper by topical or foliage treatment, representing contact action. On the other hand, the insecticidal activity of benfuracarb was higher, and comparable to its parent methylcarbamate insecticide, carbofuran, when applied by Parafilm test method, allowing the planthoppers to ingest the insecticide solution through a stretched membrane, i.e., representing direct oral toxicity. Soil treatment with benfuracarb in an aqueous solution, or in granular formulation, applied at the base of a potted rice plant, was at least as, or possibly more, effective than carbofuran because of the oral toxicity and/or systemic activity. It was determined that, on a weight basis, benfuracarb was one-eighth as effective as carbofuran under topical application, but was almost equal to it using Parafilm test method. When plant-base drench application was used, benfuracarb was as effective as carbofuran, and with granular application it was slightly superior to it. Because of its higher molecular weight, as compared to carbofuran (1.8 times greater), benfuracarb is considered to be more effective than carbofuran for soil application.