Effects of insecticide-free potato cultivation on the occurrence of aphids, their predators and tuber yield.

The effectiveness of insecticide-free cultivation for controlling the direct sucking damage of aphids in the potato field was investigated for five years under field conditions in Hokkaido, Japan. In the field plot without insecticide application, indigenous predators, such as ladybirds, minute pirate bugs, lace wings and syrphid flies, were observed and there were no outbreaks of Aphis gossypii (or other aphid species); i.e., the density of A. gossypii did not exceed 10 insects per compound leaf. Furthermore, there were no other harmful insect pests. As a result, both the tuber yield and starch value were comparable to those in the insecticide-treated plot. There were no differences in these findings by year, region, or potato cultivar.