Insecticidal activity of methanol extracts from Tephrosia purpurea

Insecticidal activity of methanol extracts from every part of Tephrosia purpurea was reported for the first time. The result showed that T.purpurea possessed insecticidal activity against the 4th instar larvae of Aedes albopictus Skuse, the 3rd instar larvae of Prodenia litura, the 3rd instar larvae of Pieris rapae (L.), and adult of Phyllotreta striolata (Fabricius). The LC_ 50 value of methanol extracts from the seeds, the stem bark, the root bark, the bean-pod, the branch, and the leaf against the 4th instar larvae of A. albopictus were 22.1, 97.7, 36.6, 142.6, 165.6, and 618.3 mg·L -1 at 24 h after treatment,respectively. The xylem of trunk did not present insecticidal activity. The methanol extracts from the seeds,the stem bark, and the root bark possessed contact toxicity against the 3rd instar larvae of P. rapae,with corresponding LC_ 50 value of 232.1,206.3,and 236.7 mg·L -1 at 24 h after treatment. The methanol extracts from the seeds, the stem bark, the root bark, the branch, the leaf, and the bean-pod exhibited stomach toxicity against the 3rd instar larvae of P. rapae,with respective LC_ 50 values being 192.6, 168.4, 249.7, 524.5, 1 001.0, and 510.7 mg·L -1 at 24 h after treatment. Reduction of food consumption and growth inhibition for the 5th instar larvae of P. rapae were sublethal effect after the insect pest contact or eat leaf disc with extracts from active part. The findings suggested as follows: every part of T. purpurea except xylem of trunk exhibited insecticidal activity. The action mode were stomach action and contact action.