Title: Effects of Chemicals on the Population of Amblyseius womersleyi SCHICHA (Acari: Phytoseiidae) and Tetranychus Kanzawai KISHIDA (Acari: Tetranychidae) When the tops and the Inside of Tea Bushes Were Sprayed
Abstract: The effects of chemicals on the population of the predatory mite Amblyseius womersleyi and its prey Tetranychus kanz-awai were evaluated when the tops or the inside of tea bushes were sprayed. The population densities of both species were counted from April to November in 1997, and chemicals were sprayed six times during the experiment. The densities of both species in the plot where the tops of the bushes were sprayed were the same as those in the untreated plot. The density of T. kanzawai in the plots where the tops and the inside of the bushes were sprayed was significantly higher than that in the untreated plot. Chemicals sprayed on the plucking surface did not significantly affect the predatory mite population, but spraying inside the leaf layer had significant effects. However, A. womersleyi controlled the population of T. kanzawai quite well even in the plot with inside spraying. Since the leaf layer of the tea bushes effectively blocked the penetration of chemicals, the.bush below the plucking surface is very important as a refuge for natural enemies.