Effects on the Bioactivity of the Extracts from Myoporum bontioides Against Imported Cabbage Worm (Pieris rapae)

The significant antifeeding action and poisoning of the extracts from Myoporum bontioides against Pieris rapae L. were reported in this paper. The antifeeding rate with 1% methanolic extract andpetroleum ether extract from leaves and stems were above 90% against 3rd instar lareae, and 80% ~86% and 46% ~ 65% against 4th and 5th instar larvae of the insect pest in no-choice tests, respectively. After treatment with methanolic extract and petroleum ether extract in 72h, 86. 1% and 88. 5% ofmertality were obtained, respectively. The LC50 of the extract partitioned with chloroform and methanolfrom methanol extract against 4th instar larvae were 0. 63% and 1. 39%, respectively. In four days aftertreatment, with 1% chloroform extract partitioned from methanol extract, the average weight of 5th instarlarvac was 38. 05% of that in control, and the emergence rate of adult was 4.00% and the rate of growthinhibition was 88. 89%.