[Bioactivity of azadirachtin and its field efficiency against Spodoptera litura].

In this paper, the effects of varying concentration azadirachtin on tobacco cutworm Spodoptera litura were investigated in both laboratory and field. The results showed that azadirachtin exhibited a wide range of bioactivities, including anti-feeding, growth inhibition, larval toxicity, and oviposition deterrent. This compound could significantly reduce pupal weight and pupation and eclosion rates. After treated with 12 microl x L(-1) azadirachtin for 5 and 7 days, the third instar larvae only weighted 36.8% and 14.5% of the untreated ones, and their development took approximately 6 days longer, with a 27.79% pupation rate and a 37.23% emergence rate, significantly lower than the control by 85.66% and 82.11%, respectively. Azadirachtin was more efficient for the low instar larva than the old ones. Field experiments confirmed that after 7 days application, azadirachtin could effectively control Spodoptera litura, being more efficient than the chemistry pesticide, 10% Chu-Jin SC.