author(s)
K Sankara Rao, R Vishnupriya and K Ramaraju

abstract
The present study was conducted to determine the effective predator-prey ratio of N. longispinosus at Insectary, Department of Entomology, Tamil Nadu Agricultural University, Coimbatore during the September 2014 to April 2015. The results revealed that Predator-prey ratio 1:10 was quite effective to other predator-prey ratios, where it contributed the mean mite reduction of 97.32 and 55.05 per cent in the laboarortory and greenhouse respectively. Further, the greenhouse study indicated that next to 1:10, predator-prey ratios 1:20 and 1:30 were equally effective in reducing the spider mite population with mean reduction of 46.02 and 39.76 percent respectively. In safety studies, dicofol was found to be highly toxic to adults (LC50 = 0.006 ppm) followed by Fenpyroximate (0.026 ppm), Fenazaquin (0.084 ppm), propargite (0.091ppm). Spiromesifen was found to be moderately toxic (0.524 ppm) whereas, hexythiazox was found to be less toxic with higher LC50 value of 1.641 ppm