Relative Abundance ofHelicoverpa armigera(Lepidoptera: Noctuidae) on Different Host Crops in India and the Role of These Crops as Natural Refuge forBacillus thuringiensisCotton

Helicoverpa armigera (Hubner) infests many economically important crops in India, including cotton, pigeonpea, chickpea, sunflower, corn, chili, tomato, and okra. These crops are cultivated in proximity to each other in central and southern India. The current study examined the relative abundance of H. armigera on different host crops within a crop mosaic. Field studies conducted over two growing seasons (2000-2001 and 2001-2002) indicated differences in egg and larval densities among the host plant species. All of the host crops supported eggs and larvae of H. armigera, but the populations on pigeonpea and chickpea were significantly greater than on cotton and other host crops. Egg numbers also were significantly higher on sunflower, okra, and tomato than on cotton, but larval numbers were not significantly different from cotton at comparable times. Both egg and larval numbers on corn and chili were not significantly different from those on cotton. This study demonstrates that a number of host crops of H. armigera support large populations at the same time that cotton is infested. Thus, these crops may act as important sources of refuge for Bacillus thuringiensis cotton plantings in central and southern India.