Insecticide dose and seasonal timing of trunk injection in apples influence efficacy and residues in nectar and plant parts

Abstract

Background: Trunk injection is an established method for delivering pesticides in ornamental and shade trees, but further research is needed to determine efficacy and pollinator safety in tree fruit crops. Apple trees were injected in 2013 and 2014 with the insecticides emamectin benzoate, imidacloprid, dinotefuran, spinosad, chlorantraniliprole, or abamectin. Additional emamectin benzoate and imidacloprid injections were performed in the spring and fall of 2015. Nectar and pollen were sampled in the following spring to compare the effects of application timings on insecticide loading into flowers.

Results: Neonicotinoids reduced Empoasca fabae density in the field. Emamectin benzoate, chlorantraniliprole, and abamectin resulted in moderate to high mortality and reduced Choristoneura rosaceana feeding in bioassays. Imidacloprid was not detected in nectar or pollen when injected in the spring, and was detected at 0.39 ng g^-1 in pollen when injected the previous fall. Emamectin benzoate was not detected in nectar or pollen when injected the previous fall, and was detected at 7.36 ng g^-1 (nectar) and 1.15 ng g^-1 (pollen) when injected in the spring.

Conclusions: This study identified a broader list of possible trunk-injectable pesticides for apple trees. This study also shows that managing the seasonal timing of injection can reduce the risk of insecticide exposure to pollinators. © 2018 Society of Chemical Industry.

Keywords: Choristoneura rosaceana; Empoasca fabae; nectar; neonicotinoid; pollen; trunk injection.