Indiscriminate use of pesticides in today's intensive agriculture has made the crop ecosystem free of natural enemies, in turn affecting the tritrophic interaction (host, pest and parasitoid). Natural enemies Hence development of resistant natural enemies is the need of the hour to make IPM a success, which aims at maintaining the pest population at a level without causing any ill effects on the environment. In India efforts were being carried out to develop insecticide resistant strains of bioagents such as Trichogramma, a most commonly used efficient egg parasitoid. Cotton bollworm Work was initiated at the Project Directorate of Biological Control (PDBC), Bangalore to develop an endosulfan tolerant strain of T.chilonis for use in cotton and other crop ecosystems against lepidopterans, especially cotton bollworm. A strain physiologically tolerant to endosulfan was developed by treating the parasitoid with endosulfan. This strain took more than 325 generations and about eight years of time to achieve the task. The product developed was transferred to M/s. Excel Industries, Mumbai and the company has already started using the tolerant strain of T.chilonis on a large scale in many states. This strain named as