Abstract
The control threshold and the tolerable injury level for the rice leaf beetle, Oulema oryzae KUWAYAMA, an important rice insect pest in northern Japan, were studied from 1974 to 1977 in Akita, Japan.Adults of the rice leaf beetle oviposited egg-masses on rice leaves in early June, and larvae injured leaves from mid to late June. The relation between damage and rice yield was examined in experimental paddy fields. From these experiments, the tolerable injury level was set at 20% injured leaves in late June. From surveys on egg-mass density and percentage of injured leaves in various paddy fields, the control threshold was estimated at 0.5 egg-masses per hill in early June.If this control threshold is adopted in Akita Prefecture, insecticide applications for the rice leaf beetle can be reduced.
