POTENTIAL FOR BIO-MANAGEMENT OF HELICOVERPA ARMIGERA HÜBNER ON TOMATO THROUGH COMBINATIONS OF MICROBIAL AGENTS

Abstract

The present study was aimed at evaluating the insecticidal efficacy of different microbial agents against Helicoverpa armigera, the voracious pest of tomato. The study comprised of the series of experiments conducted to determine the extent of field evolved resistance in H. armigera against conventional and new chemistry insecticides, to evaluate the endophytic capacity of Beauveria bassiana into tomato plants, to evaluate the lethal action of B. bassiana, B. thuringiensis and HaNPV under laboratory, green house and field conditions against H. armigera. Finally the effect of microbial agents was determined on the survival of natural allies, and the economics of application of microbial agents was calculated from yield harvested. Endophytic colonization of B. bassiana not only lowered the damage infestation of H. armigera but also improved the plant health. Synergistic effect (CTF≥20) on the mortality was observed when larvae were exposed to simultaneous application of higher concentration of B. bassiana and lower concentration of B. thuringiensis both in case of second and fourth instar H. armigera larvae. Lower concentration of B. bassiana yielded additive effect in combination with Bt. Higher concentration of NPV also integrates synergistically with lower concentration of Bt. Lower concentration of NPV works independently with higher and lower concentration of Bt. Percent pupation, adult emergence and egg eclosion from surviving individuals was found inversely correlated to toxic level of microbial agents. Increase in larval and pupal duration while decrease in pupal weight and adult duration was recorded depending upon the lethal action of the applied agent. The toxic nature of microbial agents also influenced the weight gain, frass production and diet consumption. Foliar application of B. bassiana and B. thuringiensis was found significantly persistent up to 12 days and mortality of second and fourth instar larvae was decreased with the time. Microbial agents in simultaneous application are proved to be effective in lowering the larval density of H. armigera and hence lowering the yield losses. Microbial agents are relatively safe to natural enemies of H. armigera and hence proved to be eco-safe agents. Maximum marginal return was obtained in combined application of microbial agents than their individual application