Control strategy of bean aphid with predator, Menochilus sexmaculatus (F.) and insecticides.
Field trials were conducted on the response of the predator, M. sexmaculatus [Cheilomenes sexmaculata], and insecticides to control bean aphid, Aphis craccivora during the bean [Lablab purpureus] growing season in Bangladesh. The predation rate and controlling efficacy were based on the population of aphids in lablab plants. Five larvae of C. sexmaculata caused 73-95% suppression of infesting bean aphids at high densities (490-640) and 86-100% reduction at low densities (105-180) on caged bean plants in 7 days. C. sexmaculata larvae (10 or 15 individuals) were able to control 97 and 100% aphids at a density below 500 per plant. Spraying of diazinon and malathion (at 0.002% active ingredient) controlled 80 and 87% aphids, respectively. The efficacy of 15 larvae of C. sexmaculata per bean plant was significantly greater than the 2 insecticides in controlling bean aphid and increasing yield.