Effect of Spinosad against Major Insect Pests and Natural Enemies in Rice Ecosystem

Field experiments were carried out to evaluate the efficacy of spinosad 45 SC, a biological product from actinomycetes, Saccharopolyspora spinosa @ 45 and 54 g a.i/ha in comparison to three other insecticides, viz., lambdacyhalothrin (12.5 g a.i./ha), chlorpyriphos 50% + cypermethrin 5% @ 344 g a.i./ha and monocrotophos @ 500 g a.i./ha as check against major insect pests of rice at Regional Agricultural Research Station, Pattambi, Kerala Agricultural University for three seasons viz., Kharif 2005, Rabi 2005 and 2006. Pooled analysis of three crop seasons indicated that spinosad @ 54 g a.i./ha was the most effective against rice stem borer, gall midge, leaffolder and whorl maggot. It caused 63 and 49 per cent reduction in dead hearts and white ears, respectively. The lower dosage of spinosad @ 45 g a.i./ha reduced whorl maggot infestation by 34 per cent. Spinosad @ 54 g a.i./ha resulted in 94 per cent reduction in leaffolder and 50 per cent reduction in gall midge infestation. Spinosad treatment also resulted in 14 per cent increase in rice yield. Spinosad caused no significant effect on spider population and was safe to spiders that predominate the predatory fauna in rice. Monocrotophos and lambdacyhaiothrin significantly reduced the spider and larval parasitoid populations in the rice ecosystem.