Developing a method of beech sawfly control by trunk injection of dinotefuran for conserving beech forests

Abstract

We investigated the effect of trunk injection of dinotefuran at different time points (before and after the leaf opening period when eggs were laid) and distances (15 and 25 cm intervals on perimeters). In addition, the residual effectiveness after a year was investigated. The effect on eggs was significantly higher when the chemical was injected before the leaf opening period than after it or when the chemical was not injected or injected in the previous year. Additionally, the effect on larvae was significantly higher when the chemical was injected before or after the leaf opening than when it was injected in the previous year or not injected. Feeding damage was suppressed to under 10% by the chemical injection, irrespective of timing and interval distance, even though the density of eggs laid was high. To maintain a high effect of injection while reducing injuries on the tree trunk, a 25 cm-interval injection might be appropriate. The influence against nontargeted insects utilizing beech leaves was possibly limited to a single year.