Population dynamics of major defoliators of rice

The field study carried out at College of Agriculture, V C Farm, Mandya, Karnataka evaluated the seasonal incidence of the major defoliators of rice viz., rice hispa, leaf folder, caseworm and horned caterpillar during kharif 2018-19. The results revealed that the peak incidence of rice hispa (1.63 grub/ 20 hills) and horned caterpillar (2.87 larvae/ 20 hills) was observed in October. While for the leaf folder (8.41 larvae/ 20 hills) and caseworm (8.29 larvae/ 20 hills), peaks were during November. The correlation coefficients of incidence with weather factors revealed a positive relationship with morning relative humidity (RH), rainfall, maximum temperature, while it was a negative one with sunshine hours, minimum temperature and mean afternoon RH. The leaf folder incidence revealed a positive association with sunshine hours, mean minimum and maximum temperature, and with the rainfall and morning RH it was negative. The caseworm incidence revealed a positive correlation with morning RH, sunshine hours and maximum temperature, and with rainfall and afternoon RH it was negative; horned caterpillar showed a positive correlation with afternoon RH, minimum and maximum temperature and mean sunshine hours, while it was a negative one with rainfall and morning RH.