We investigated the occurrence of pearleaf worm larvae in an unsprayed apple orchard in Morioka City,Iwate Prefecture, over four years using double-sided adhesive tape traps. Most of the larvae were captured from mid-July to early August, with a peak in late July. The peaks corresponded to a temperature accumulation from 660.6 to 757.3 degree-days at a base temperature above 10 ℃ from March 1.
