Economic Injury Levels and Economics of Control of the Mustard Aphid, Lipaphis Erysimi (Kalt.) on Mustard in Tarai, India

The economic injury levels (EIL) of the mustard aphid, Lipaphis erysimi on mustard, Brassica juncea were evaluated in field trials in Tarai, India, during the winters of 1986/87 and 1987/88. The EIL values ranged between 37 and 4, and 48 and 6 aphids per 10 cm terminal shoot per plant during the 1986 / 87 and 1987/88 trials respectively. A one-day increase in crop exposure to the aphids led to a significant reduction in seed yield per plant, 1000-seed weight, number of siliquae per plant and number of seeds per siliqua. The highest benefit-to-cost ratio was obtained at 3 weeks of exposure, when initiation of insecticide application was most economical