Abstract
Effects of insecticides on the biodiversity in paddy fields were investigated in Tohoku district. Test paddy field (10a) was divided into four areas, i.e., (A) control area; (B) imidacloprid applied area; (C) imidacloprid and cycloprothrin applied area; (D) imidacloprid, cycroprothrin, and ethofenprox applied are Imidacloprid, cycloprothrin and ethofenprox were applied on 26 May, 25 June and 29 July in 1998, respectively. Population density of aquatic organisms and natural enemies decreased by the insecticide applications. Particularly, that of C and D areas was affected significantly. On the contrary, the density of pests was siginificantly decreased even in B area. The results suggested that single insecticide application such as imidacloprid is preferable for protecting the biodiversity (natural enemies and aquatic organisms) in paddy fields. if we are forced to control pests by insecticides.
