Application of Granular Insecticides for Toxicity against Insect-pests and Safety to Fish in Paddy-fish Culture

Methods of application of different insecticides were evaluated for effectiveness against insect-pests and safety to fish in paddy-fish culture. Rice root-zone placement of carbofuran granules @ 1.0 kg a.i. ha⁻¹ in the form of clay soil balls was found effective and safe to the released common carp, Cyprinus carpio carpio Lin. fingerlings. It was found superior to the granular formulations of phorate, quinalphos and HCH, when applied by root-zone placement in clay soil balls, root-zone placement in cowdung balls and two split broadcastings on 30 and 60 d after transplanting (DT). Rice root-zone placed granules of all the four insecticides in clay soil balls lasted longer in effectiveness against insect-pests in comparison to the other two methods of application. When root zone placement of carbofuran @ 1.0 kg a.i. ha⁻¹ was compared with its two split broadcastings, two split broadcastings of phorate @ 1.0 kg a.i. ha⁻¹ and fortnightly sprays of quinalphos (0.05%), it was found significantly superior in effectiveness against Hydrellia sp., Sogatella furcifera Horv. and Cnaphalocrocis medinalis Guen. Rice yield was found significantly high in rice root-zone placed carbofuran. Fish yield, on the other hand, was significantly high in the untreated control followed by the quinalphos (0.05%) sprays at 15 d interval and single cabrofuran application at the rice root-zone on 21 DT.