Emamectin benzoate 9.7% SL as a new formulation for a trunk-injections against pine wood nematode, Bursaphelenchus xylophilus

Abstract

In this study, we investigated the preventive effects of emamectin benzoate 9.7% SL, which was newly developed to reduce the injection volume and number of injection holes required to protect against pine wood nematode. None of the Pinus thunbergii trees injected with emamectin benzoate 9.7% SL at 0.3 mL/cm diameter at breast height (DBH) died within 2 years of inoculation with pine wood nematodes. Emamectin benzoate 9.7% SL injected at 0.6 mL/cm DBH resulted in no tree mortality for 3 years. Mean residue of emamectin benzoate 9.7% SL in pine twigs injected with 0.3 mL/cm DBH was 0.490 μg/g at 1 year after injection and 0.303 μg/g after 2 years. These residues values are greater than 0.031 μg/g, previously determined IC95 value for emamectin benzoate against the pine wood nematode. Our field experiment and residue analysis showed that emamectin benzoate 9.7% SL could be a substitute agent for emamectin benzoate 2.15% EC, which is widely used to prevent pine wood nematode in the field and that injection volume and number of injection holes can be greatly educed using this new formulation, which will reduce injury to the cambium, interruption of water movement, and infection of inoculation wounds by wood-decay or blue stain fungi.