COMPARISON OF INSECTICIDE SUSCEPTIBILITY BETWEEN FALL WEBWORM, HYPHANTRIA-CUNEA (LEPIDOPTERA, ARCTIIDAE) AND ITS PARASITOID FLY, EXORISTA-JAPONICA (DIPTERA, TACHINIDAE)

The insecticide susceptibility of the Fall Webworm, Hyphantria cunea a nd its parasitoid fly, Exorista japonica, was studied. Larvae of H. cu nea were hardly susceptible to organophosphorus insecticides, such as fenitrothion (LD50 = >100 mu g/larva) and isoxathion (LD50 = 54 mu g/l arva). However, adults of H. cunea were quite susceptible to fenitroth ion (LD50 = 1.4 mu g/male and 2.2 mu g/female). Adults of E. japonica emerging from pupa of H. cunea were very susceptible to fenitrothion ( LD50 = 0.082 mu g/adult). The results suggest that a judicious choice of insecticide is necessary to control H. cunea, if E. japonica is use d as a biological control agent, too.