Study on the use of neem seed extract formulated by DOA for the control of beanfly in mungbean

Beanfly is one of the most important pests of mungbean seedlings, which frequently causes death of seedlings or reduced growth and obtainable yield. The seeds of Thai neem tree, Azadirachta indica var. siamensis Valeton contain Azadirachtin (Aza) the chemical substance showing insecticidal effects to many insect pests. The preparation of aqueous neem seed kernel extract for spraying is generally not simple for many Thai farmers. Thus, the neem seed kernel extract formulated by Department of Agriculture (DOA neem) was produced for mixing with water to spray instantly and easily. The objective of this study was to investigate the efficacy of the DOA neem for the control of beanfly in mungbean. Field study was conducted at Chai Nat Field Crops Research Center in dry season 1999. The DOA neem containing Aza A 100, 80, 60, 40, 20 ppm concentration were sprayed in mungbean plots in every 4 day interval for 3 times starting after emergence at the stage of the unifoliate leaves are unfolded and begin expanding (VC stage). All treatments were compared with the spraying of triazophos 40 percent EC at the dosage of 40 ml/20 litres of water in every 7 day interval for 2 times starting at the same stage and with the untreated control. The experiment was in RCB with 3 replications. The results revealed that the mungbean plots sprayed with DOA neem with Aza A 20-100 ppm had average beanfly, Ophiomyia phaseoli (Tryon) at 3 weeks after emergence 0.0-1.7 larvae and pupae (L+P) / 40 plants and had average damaged plants 0.8-9.2 percent which were considerably low and not significantly different from those of the mungbean plots sprayed with triazophos which had no L+P / 40 plants and had average damaged plants only 2.5 percent. Instead, the untreated mungbean plots had average 32.3 L+P / 40 plant and had average damaged plants average 80.8 percent which were entirely high. Then, it may be generally concluded that the spraying of the DOA neem with 40 ppm Aza A and over in mungbean plots showed high efficacy for controlling beanfly (O. phaseoli) as that of the triazophos 40 percent EC at the dosage of 40 ml/20 litres of water. Besides, it was found that the DOA neem had repellent effect to adult beanflies. Nevertheless, the spraying of the DOA neem with 40 ppm Aza A caused 27 percent phytotoxicity to mungbean leaves which was not significantly different from that caused by the spraying of triazophos.