Interactive Effect of Chickpea Genotypes and Nuclear Polyhedrosis Virus on the Management of Helicoverpa armigera (Hubner)

The gram pod borer, Helicoverpa armigera (Hubner) is the major pest of chickpea in India. Reduced efficacy of chemical insecticides against H. armigera in the recent past encouraged workers to consider alternatives for managing this pest. Malic acid found in exudates of chickpea leaves and pods, was reported to be a marker for resistance to H. armigera. Other workers observed that the activity of nuclear polyhedrosis virus reduced under highly acidic conditions. Therefore, to understand the interactive effect of chickpea genotypes in context with different levels of malic acid, and nuclear polyhedrosis virus on H armigera management, an experiment was taken up during two post rainy seasons of 1989–90 and 1990–91. Weekly observations were recorded on 20 plants per plot to estimate the population level of H. armigera larvae. Two sprays were applied when the pest population was at one larva per plant. The data on pest counts were also collected at three, seven and 15 days after each spray. The individual or combined applications of H. armigera nuclear polyhedrosis virus (HaNPV) @ 250 LE ha⁻¹ or/and endosulfan @ 0.07% proved more effective in controlling H. armigera on the susceptible genotypes than on the resistant ones. Application of synthetic malic acid (3%) on plants did not reduce the effectiveness of HaNPV, but did not cause much additional reduction in larval populations. When treated with HaNPV (@ 250 LE/ha) plus endosulfan (0.07%), the susceptible cvs PG 5 and Annigeri recorded higher yield than the resistant cultivars ICC 506 and AKG 35. Yields progressively reduced with the applications of endosulfan, HaNPV. HaNPV plus malic acid, HaNPV after water-wash, malic acid alone and control.