Abstract

                                Evaluation of new insecticide molecules is inevitable in agriculture to overcome insecticide resistance development in agricultural and horticultural crop pests. Experiments for assessment of bioefficacy of fipronil 80 WG against grapes thrips was conducted in two seasons at Madhampatti village, Thondamuthur, Coimbatore. Fipronil 80 WG at five different doses (30, 40, 50, 80 and 100 g a.i. ha-1), fipronil 5 SC in two different doses (40 and 50 g a.i. ha-1), chlorpyriphos 20 EC @ 200 g a.i. ha-1 along with untreated check were taken as treatments for the evaluation. After imposing the treatments twice at fifteen days interval, the highest pest reduction was noticed in plots treated with fipronil 80 WG @ 100, 80, 50 and 40 g a.i.ha-1 to the tune of 82.17, 81.67, 81.04 and 80.35 % over untreated check, respectively. Among the various treatments, fipronil 80 WG @ 100 g.a.i.ha-1 recorded a significantly higher fruit yield of 8.23 t ha-1 which was on par with fipronil 80 WG @ 80 g.a.i.ha-1 (8.17 t ha-1) and 50 g.a.i.ha-1 (8.00 t ha-1). Grapes sprayed with fipronil 80 WG @ 50, 100 and 200 g.a.i.ha-1 doses did not show any phytotoxic effects like epinasty, hyponasty, leaf injury, wilting, vein clearing and necrosis. To conclude, fibronil 80WG @ 50 g a.i. ha-1 was recorded on par with other higher doses in reducing the thrips population and increasing the fruit yield. Hence, fibronil 80 WG @ 50 g a.i. ha-1 may be recommended for the management of thrips in grapes.

Key words : Fipronil, Grapes, Thirps, Bioefficacy, Phytotoxicity