Evaluation of Age Related Response of Spilarctia obliqua (Walker) to Biorational Insecticides

The biorational insecticides were neem seed kernel extract (NSKE) (3.0, 4.5 and 6.0%), cow urine (10, 15 and 20%), diflubenzuron 25 WP (0.028, 0.056 and 0.112%) and triazaphos 40 EC (0.026, 0.053 and 0.11%). The treated leaves of soybean with different insecticides were fed to larvae of different age groups of S. obliqua and the observations were recorded on the mortality of larvae. A significant increase in mortality rate was observed at all the concentrations of triazophos and two highest concentrations of NSKE and diflubenzuron 25 WP. However, in the cow urine, there was only 33.3% and 10.0% mortality after 15 days of exposure in 4.5 and 1516 days old larvae of S. obliqua, respectively. With the increase in the age of larvae, the toxicity of insecticides also decreased.