Effect of two microbial bioagents on the tomato borer, Helicoverpa armigera (Hubner) (Lepidoptera:Noctuidae)

The polyphagous insect, Helicoverpa armigera has become a serious pest in the recent years causing extensive damage to several crops in many parts of India. In view of its reported development of resistance to insecticides and the hazards of pesticide residues in vegetables, an attempt was made to study the effectiveness of two microbial bioagents, Bacillus thuringiensis and Nuclear polyhedrosis Virus, against the tomato fruit borer for their suitability in the Integrated Pest Management. The LC50 value for Bacillus thuringiensis var Kurstaki against the third instar larvae of H. armigera was found to be 230 ppm. Spraying the crop with 1000 ppm of the commercial formulation (Delfin) gave 90% mortality whereas a crude extract of nuclear polyhedrosis virus of H. armigera at 1500 LE/ha resulted in only 40% mortality of third instar larvae of the pest.