Efficacy of Cypermethrin, Neem Extract and Bacillus thuringiensis for Controlling Insect Pests of Vegetable Soybean

Field experiments were conducted during dry and wet seasons (1999-2000) at Kamphaeng Saen Campus of Kasetsart University, Nakhon Pathom, Thailand to evaluate the efficacy of cypermethrin 10 EC, neem extract (Azadirachtin 0.1%) and Bacillus thuringiensis var. kurstaki (53,000 SU/mg) in controlling the major insect pests of vegetable soybean. Melanagromyza sojae, Spodoptera litura, Spodoptera exigua, Helicoverpa armigera, Lamprosema indicata, Etiella zinckenella and Bemisia tabaci were the most abundant species in both seasons. Insecticides were sprayed at 10 days interval until harvest. Cypermethrin showed significantly better control among the treatments. Neem extract moderately suppressed the insect pests with statistically significant efficacy over the control. B. thuringiensis var. kurstaki showed less efficacy than neem extract but exhibited statistically significant efficacy over the control in most cases. Highest yield was recorded in cypermethrin treated plot (9.83 t/ha) followed by neem extract (8.39 t/h), B. thuringiensis var. kurstaki (7.98 t/ha) and control (6.22 t/ha) in dry season whereas yields were 5.83, 4.83, 4.0 and 2.83 t/ha for cypermethrin, neem extract, B. thuringiensis var. kurstaki and control in wet season, respectively. Additionally, Menochilus sexmaculatus and spider were found less in cypermethrin treated plots whereas in other treatments they were significantly higher in number.