Planting chickpea as trap crop to reduce the population of American bollworm Helicoverpa armigera (Lep: Noctuidae) in cotton fields.

To determine the effect of trap crop in reducing the population of American bollworm Helicoverpa armigera(Hub.) chick pea was planted in 0.5 hac.of the Cotton Research Station of Hashemabad, Gorgan (about 1% the total cotton acreage of this station) in early Mars of 2006- 07. Samplings in chick pea were started with the beginning of the pest activity and continued every 5-7 days.The trap crop was ploughed in mid June to eliminate the existed larvae and pupae of H. armigera.To compare the density of the pest in the succeeding crops a tomato field in the neigbore of the station ( only in 2007) and four plots of cotton inside the station (both years) in distances 5, 100, 200 and 300 meters from trap crop were selected, and weekly samplings were done on them. The results showed that in chick pea the mean larval density of H. armigera per plant in 2006-07 were 0.3 and 0.32 respectively . The peak larval number of H. armigera in this two years were 0.52 and 0.62 respectively. The number of eliminated larvae of H. armigera in chick pea in 2006-07 were 43000 and 51000 respectively. which is a considerable number for the tested region because H. armigera female has high fecundity and its population increases sharply from one generation to the succeeding generation. In tomato mean larval density of H. armigera was 16 times less than chick pea. In cotton mean larval density of H. armigera in 2006 were 16.6, 10.7, 5.4 and 13 times and in 2007 were 12.6, 5.8 9.1 and 4.9 times less than the density of the pest in chick pea in the same year in distances 5, 100, 200 and 300 meters from trap crop respectively .In cotton insecticide was used only one time in some plots for H. armigera control in both years which was less than the average anual amount of insecticide useage against this pest in the region (between 2-3 times). Overall it is concluded that planting chick pea as trap crop and killing the attracted population of H. armigera could be a suitable method in Integrated Management of H. armigera in cotton.