Effect of Weather Parameters on Population Buildup of Different Insect Pests of Rice and Their Natural Enemies

Abstract

The effect of weather parameters on population buildup of some major rice pests viz., stem borer, whorl maggot, leaf folder, and gundhi bug and their natural enemies viz., spiders, dragonfly/damselfly, lady bird beetle and Apanteles was studied by taking observations at fortnightly interval starting from second fortnight of July to first fortnight of November through fixed plot survey during kharif, 2007 and 2008 at ICAR Research Complex for NEH Region, Sikkim Centre, Tadong. It was observed from the study that the whorl maggot started the infestation at the initial stage of the crop and damaged maximum (22.25 -24.25 damaged leaves/10 hills) in the second fortnight of July. Stem borer infestation was found maximum during August-September (6.82–7.62% dead heart). They also attacked the rice crop at reproductive stage which resulted in white ear head. The maximum white ear head% was recorded in the second fortnight of October (7.56 % in 2007 and 8.14% in 2008). The leaf folder population was found maximum in the last part of August and first part of September (14.50 -16.75 damaged leaves/10 hills). Gundhi bug population was found maximum when the crop attained the milky stage in the first fortnight of October (14.80-16.40 gundhi bug/10 hills). Among the natural enemies the population of spiders, Apanteles and dragon flies was recorded during August and September but the lady bird beetle population was found maximum during the last fortnight of September. The correlation study revealed that the population build-up of different pests and their natural enemies was influenced by the weather parameters in both the years.