Joint toxic action of chitin inhibitor (lufenuron) and insecticides in the management of Plutella xylostella Linn. infesting mustard

The joint toxic action of a new chitin inhibitor, lufenuron, in combination with certain insecticides was studied against the diamond back moth, Plutella xylostella Linn., infesting mustard during 1995–96. The crop was sprayed twice at 18-day interval. The number of larvae/10 plants was recorded one day before spraying and on 2, 7, 12 and 17 days after spraying. Polytin C (0.066%) was the most effective two days after spraying, followed by cypermethrin (0.02%). After 7, 12, and 17 days, the combination, viz., lufenuron (0.025%) + cypermethorin (0.01%) was the most effective, followed by various combinations with lufenuron. Among the treatments, Bacillus, thuringiensis (0.15%) and neem oil (1%) were less effective consistently. Lufenuron (0.05%) was less effective on 2^nd day after spraying but its efficacy improved by 7^th day. The overall efficacy indicated that the combinations of insecticides with lufenuron were more effective, besides being less toxic to the natural enemies.