茶園におけるナミテントウのカンザワハダニ捕食と発生生態

抄録

Adults and larvae of Asian lady beetle, Harmonia axyridis (Pallas), were discovered preying on the spider mite, Tetranychus kanzawai Kishida infesting leaves of tea shoots in an unsprayed tea field in 1992. When H. axyridis was given tea leaves infested with T. kanzawai in the laboratory, predation of spider mites by H. axyridis was observed. Furthermore, consumption of the adult female T. kanzawai prey by H. axyridis was investigated. Adult H. axyridis preyed on 41.5 spider mites per day when given 71 spider mites per leaf disk (diameter approx. 33mm), and larva preyed on 38.7 spider mites per day when given 40.7 spider mites per leaf disk. The three species of lady beetles, H. axyridis, seven-spotted lady beetle Coccinella septempunctata Linne, and Propylea japonica (Thunberg), were observed on the plucking surface of the tea bushes before the harvest of the first crop of tea. Adult H. axyridis were mainly observed. However, only a few larvae were on the plucking surface of the tea bushes in the tea season of the first crop, which is from the beginning of May until the middle of May. The number of adults increased after the middle of May. However, adults almost disappeared in June, whereas the number of larvae increased rapidly after plucking tea shoots in June.