Study on the efficacy of neem oil and neem-extracted substances on the rice leaf-hopper, Nephotettix virescens (Distant)
1987
Unchalee Songkittisuntorn
The goal of this study was to make the most out of neem seed. In the first step, neem oil was extracted by hexane, after which the remainder was then extracted by water as to be the main solvent. The other solvents were used to increase the effectiveness of the extract as well. The investigation on the repellent property of neem oil at 10 % concentration up found such property to increase along with the increasing of neem oil's concentration. However, it was also noticed that neem extract by distillating method was more efficient to the female green leafhopper than the neem oil. The comparison of the efficacy of N1 extract, N2 extract, NIM extract and extract with pure water indicated that N1 extract showed the best result and the next in line were NIM extract, N2 extract and extract with pure water respectively. Neem oil at 7 % concentration and up was observed to reduce the population density of treated 3 rd instar nymphal green leafhopper to more than 50 %. When 0.1 % synergist piperonyl butoxide was added to 5 % neem oil, the efficacy of neem oil apparently increased by causing 42.5 % mortality more to the 3 rd instar nymphal green leafhopper. The study on the efficacy of N1 extract, NIM extract and extract with water to the 3 rd instar nymphal leafhoopper found NIM extract to give the best result with N1 extract, and extract with pure water were the next in line respectively. It was also noticed that neem oil was better than neem extract by distillation method in reducing the nymphal production of the insect and N1 extract was more efficient than NIM extract, N2 extract and extract with pure water respectively. 1.67 % N1 extract and 25 % neem oil were found to decrease mortality of female green leafhopper to lower than 50 % after 6 days of tested extract spraying
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