Insecticidal activity of a trehalase inhibitor, validoxylamine A, against the green peach aphid, Myzus persicae.

We investigated the insecticidal activity of a trehalase inhibitor, validox ylamine A (VAA), against insecticide susceptible (S) and resistant (R) stra ins of the green peach aphid, Myzus persicae. Four methods, leaf dipping me thod, two methods to determine the systemic activity using plants with root s (root soaking) and without roots (stalk-tip soaking), and parafilm method , which allows the aphids to suck artificial diet solution containing VAA t hrough the parafilm membrane, were adopted for the tests. Mortality of firs t instar nymphs 2 d after treatment by leaf dipping method with 100ppm VAA was about 10% in both S and R strains. The stalk-tip soaking method, howeve r, showed strong effects of 100% and 88.5% against S and R strains, respect ively, at 100ppm VAA. At 20ppm VAA in the root soaking method, 57.4% (S) an d 49.9% (R) of female adults were dead within 7 d. The production of nymphs by the treated female was strongly suppressed. By the parafilm method, 20p pm VAA caused complete mortality in female adults within 5 d. These results suggest that concentrations of VAA at the sucking site of the aphid was lo wer than that around the root where treatment occurred. For practical usage of these chemicals as insecticides, chemical modification is needed to imp rove the systemic characteristics.