Effect of variety and planting date of rice on population of natural enemies of brown planthopper, Nilaparvata lugens (Stal)

Abstract

The present study on the effect of variety and planting date of rice on population of natural enemies of brown planthopper, Nilaparvata lugens (Stal) showed that during August, the mean population of spiders was statistically on par on CSR 30 and PR 114. The population differed with dates and was significantly (p=0.05) higher (9.0/10 hills) in D2 during 2011 only. There was no significant difference in the population of spiders on two varieties and dates of transplanting during September 2011 only. However, significantly higher population of spiders was recorded in variety PR 114 (21.65/10 hills) and D2 (20.52/10 hills) than on CSR 30 (13.67/10 hills) and D1 (14.80/10 hills) during September, 2012. The mean population of spiders did not differ significantly with the dates during October, 2011 and 2012. However, it was significantly higher on variety PR 114 (27.65/10 hills) than on CSR 30 during both the crop seasons. Mirid bugs did not appear in the month of August, 2011 and 2012 whereas during September 2011, the variety CSR 30 and D1 registered significantly higher population than other variety and date. However, a reverse trend was observed with varieties and dates during 2012. The mean population of coccinelid, carabid and staphylinid beetles remained very low on both the varieties in the month of August during 2011 and 2012. However, the population of these predators was influenced significantly by the varieties and dates during 2012. The population of nymphal-adult parasitoids also remained very low during both years and was not influenced by varieties and dates.