Abstract
The dynamics of insect pests and the impact of the management system on commercial village farms were investigated over several years. Damage to the cotton crop by bollworms in the polycrop system increased with the advancement of crop growth, with greater application of nitrogenous fertilizers and irrigation and with reduced planting distances between the conventional varieties. The activity of the adults of Helicoverpa armigera, Spodoptera litura and Pectinophora gossypiella in this crop system was at its peak during the middle reproductive phase of the cotton crop, and subsequently declined. The foliaceous, tall growing hybrids and varieties with heavy canopies had greater infestations of the adults of the leaf-feeding insect, S. litura. Investigations carried out over several years on commercial village farms show that the insect management system was lethal to the insect complex in the cotton system. De-topping of the growing terminals of plants greatly reduced oviposition by insecticide-resistant populations of H. armigera. The manual collection of larvae and affected plant parts resulted in the reduction of bollworm infestation on the village farms by 3–90%. Liberation of Trichogramma achea in great numbers reduced the population of different species of bollworms on the village farms. This system has reduced environmental pollution with insecticides by 35–59% and contamination of labourers' and farmers' blood and female workers' breast milk by 35–76%. Increased productivity of varieties and hybrids has been maintained over an observed range (according to growing conditions) from 870 to 2,220 kg/ha of seed cotton. The population of native natural enemies of cotton insects was increased several fold and had inverse density-dependent effects on the host insects. The pest management system has been adopted in cotton-growing states with financial assistance from the government of India since 2000.
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