Plants as a source of insect growth regulators for crop protection
1987
Chiu Shin-Foon (South China Agricultural Univ., Guangzhou (China))
The potential of Azadirachta indica, Melia toosendan, and M. azedarach (family Meliaceae), Tripterygium wilfordii and T. hypoglaucum (family Celastraceae), and Tephrosia vogelii (family Fabaceae) as a source of insect growth regulators was evaluated in laboratory and field experiments. Fifty instar Pieris rapae larvae topically treated with 20 % neem oil at 2 microliter/larva developed poorly and died after pupation. In field trials, spray application of a 0.3 % neem seed extract (AZT-VR-K) was effective against P. rapae larvae for almost 21 days. The extract was also effective against Plutella xylostella. Azadirachtin disrupted the growth of corn borers and other pests. A 1% methanol extract of seed kernels of M. azedarach caused 80% feeding inhibition in first and second instar Mythimna separata larvae which developed to third or fourth instar stage only. Toosandanin, extracted from M. toosendan, bark was a strong antifeedant, stomach poison, and growth inhibitor against P. rapae larvae and controlled the fifth instar larvae when sprayed in the field at 500 to 800 ppm. Morphogenetic effects were observed in pupae, if larvae consumed toosendanin-treated leaves. Topical application of a 0.5% acetone-extract of T. vogelii leaves at 2 microliter/larva caused 89% failure in pupation, while treatment with a 0.1% acetone-extract of T. vogelii leaves killed 98% of P. rapae eggs.
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