RAGHAVAIAH, GVENKATESWARLU, P2016-07-302016-07-301988http://krishikosh.egranth.ac.in/handle/1/70319Experiments were conducted during 1987-88 in the department of Entomology and at the Agricultural College farm, Bapatla to know the effect of neem oil on certain lepidopterous pests of blackgram. Under laboratory conditions among the concentrations of neem oil (0·5 to 16.0%) tested, 8.0 and 16.0 per cent e xh ib ited cent per cent repellency and antifeedant property against both s. littu-·a and!:.!._ r·icini· The ov i position of b oth the insects was deterred as the concentration of neem oil i n creased ( 0.5 to 16-0% ) but, complete deterrency was ob serv ed at 16 per cent neem oil· The growth a n d development in r espect of adult eme r gence, g r owth index, length of larva, weight of larva and p upa decreased while the develo p menta l period increased as the concentration of neem oi l i n c l-·ease d f r om o . 5 to 4 -0%. Bu t at 8 a n d 16 per cent t he g r owt h a nd d evelopment of bot h t h e insects was complete l y supp r essed . . ' The hatchability of both s. litura and P . ricini eggs was inversly proportiona l to neem oil's concentration. Neem oil at 0.5 and 1.0 % lost its antifeedant property by 5th day and by the 6th day of treatment at 2-0% when exposed to sunlight. Neem oil at 8 and 16 per cent exhibited phytotoxic symptoms but the percentage of leaf area affected was more on castor leaves than on blackgram. Both endosulfan 0.07% and monocrotophos 0.04% were superior over neem oil in causing larval mo1··tal i ty of s. 1 it til·· a and H. a1··mi ger·a. Insecticides exhibited synergistic effect, when used along with neem oil· Under field cond itions also, endosulfan 0.07% + neem o il 1-0% recorded highest per cent reduction ( 76 -6,77-5 and 70-1%) of pod bo r er complex of blackgram (S . litur·a, H. armigera and M· testulalis) with correspon di ng i n crease i n yield (369-44 Kg/ha) compared to neem oil and i n secticides when used alone. But based on economics of treatments , endosulfan 0.07% recorded maximum net profit of Rs . 508.12/ha with net incremental cost benefit ratio of 1 Neem '- . oil 0.5 and 1.0 per cent (1 : 0-79 and 1 superior over neem oil 1-0% + endosulfan 0 -07% (1 (> . 50) and neem oil 1·0% + monocrotophos 0-04% (1 : 0 - 49) . All the treatments applied twice at 15 day interval r ecorded maximum net profits with highest cost benefit ratios than the treatments applied thrice at 10 day intervalenEFFECT, NEEM OIL, CERTAIN, LEPIDOPTEROUS, PESTS,BLACKGRAM,Thesis