Conservation Biological Control of Aphids in Potato Fields with Reduced Use of Insecticides in Hokkaido, Japan.

The possibility of reducing insecticide use for controlling direct sucking damage to potatoes by Aphis gossypii was investigated under field conditions. A laboratory experiment was also conducted to determine the possible cause of resurgence in A. gossypii treated with acephate. The susceptibility of A. gossypii to this insecticide was much lower than that of two other inhabiting aphids (Myzus persicae and Aulacorthum solani) and predators (Harmonia axyridis and Orius minutus), indicating that the resurgence of A. gossypii was probably caused by the elimination of natural enemies and competitors by this insecticide. In the field plot without insecticide application, there was no outbreak of A. gossypii (or other aphid species) observed due to suppression by indigenous predators (ex. ladybirds, lacewings, Orius bugs); e.g., the density of A. gossypii did not exceed 10 insects per compound leaf, and no other insect pests were conspicuous. Consequently, both the tuber yield and the starch value were comparable to those in the insecticide-treated plot. The indigenous predators inhabited the environment around the field over a wide area during the potato-growing season. These findings suggested that there is a possibility of realizing potato Cultivation without the application of insecticides.