Abstract

                                Twelve commercial insecticides in emulsifiable concentrates and wettable powder forms at four concentrations Viz., 0.025. 0 05. 0.075 and 0.10% a.i were evaluated in bioassay studies against adults and nymphs of brown planthopper (BPH) separately. Diaz- inon 0,05% .l concentration was taken as standard The efficacy and persistence of all other test insecticides were compared with this standard. Fresh lots of insects were relea- sed/caged periodically to find out the persistent toxicity of respective insecticides Consi- dering the overall persistent toxicity against adults and nymphs based on PT values and overall mean persistent toxicity, chlorpyrifos and carbofuran 0.05% a.l as foliar sprays followed by qujnalphos and monocrotophos are the most effective in the control of 8PH in the field.

Key words :