Abstract

Studies conducted at the Paddy Breeding Station, Coimbatore on the seasonal incidence of the rice thrips, Stenchaetothrips biformis in the rice nursery and the main field revealed a peak occurrence of the pest during the months of August and September. The pest population and its damage during the month of March were very low. The pop- ulation of thrips was higher on the weed host, Echinochloa colona during the month of March. Significant positive association was known to exist between thrips population and their damage (r=0.82) and regression equation Y 14.2 + 17.9X indicated that for an increase of one thrip, there would be an increase of 17.9% damage. The regression analyses revealed that an increase of 1% RH would increase the thrips population and their damage by 0.06 and 1.867% respectively as well as increase in sunshine by one hour would reduce the thrips population by 0.017 and their damage by 0.565% in the nursery. In the transplanted crop, increase in evening RH by 1% would increase the thrips population by 0.271 and their damage by 1.129 % as well as increase in sunshine by one hour would reduce thrips damage by 0.29%. The population of thrips on E. colona would be increased by 0.531 for every 1°C increase in minimum temperature.

Keywords: Rice, Thrips, Seasonal incidencc, Weed host