Persistence of some systemic insecticides in cowpea when applied as granules in different soil types of Kerala

Abstract

A pot trial was conducted to study the persistent toxicity of phorate, car. bofuran, mephosfolan and disulfoton to the pea aphid, Aphis craccivota on cowpea grown in sandy, laterite, red, forest and black soils treated with the above insecticides as granule. The persistent toxicity was highest in plants treated with disulfoton in all types of soils. Mephosfolan was next best in sandy, red and forest soils whereas carbofuran was next to disulfoton in laterite and black soils. The yields obtained from treated plants were significantly higher than those of corresponding controls. But there was no direct correlation between the persistent toxicity of insecticides and the yield. The yield factor appears to be influenced by the impact of the insecticide on some soil factors favouring plant growth.