Diversity of soil insects in kidney bean ecosystem and their management in North – western Himalayas

Studies on diversity of soil insects in kidney bean ecosystem revealed that maximum scarab beetles (34 and 56) were captured in the light trap during second and first fortnight of August 2004 and 2005, respectively. The cutworm moth catch was maximum (22 and 25) during first and last week of July 2004 and 2005, respectively. The grub population in soil was found to increase from June to August and declined thereafter. The average grub population (2004 & 2005) in soil under kidney bean ecosystems was maximum (1.665 grubs/cu. ft.) in the month of August. Studies conducted in the adjoining pea and buckwheat fields also indicated a similar trend with respect to grub population in soil. The species composition of scarab beetles on fruit trees (walnut, apple and apricot) revealed the predominance of Brahmina coriaceae and Holotrichia longipennis. Evaluation of some insecticides as seed treatment/soil application for the management of soil insects viz. white grubs, cut worms and weevil revealed that quinalphos and chlorpyriphos both @ 800 g a.i./ha as soil treatment and imidacloprid as seed treatment @ 4ml/kg seed were highly effective against white grubs and resulted in higher reduction in plant mortality (61.60, 59.64 and 57.88%, respectively) compared to other insecticides. These treatments along with thiamethoxam applied @ 2 g/kg seed were also effective in reducing cutworm populations. Against weevils (Strophosomoides kumaoensis Aslam), however, seed treatment with organophosphorus pesticides viz. chlorpyriphos and quinalphos @ 4 ml/kg seed was more effective resulting in 47.67 and 47.07 per cent reduction in weevil population, respectively. Although, the percent increase in yield of kidney bean over control was maximum following imidacloprid seed treatment; however, considering efficacy as well as economics, seed treatment with chlorpyriphos and quinalphos@ 4 ml/kg seed were the most effective for the collective management of all the three insect pest species.