Trunk Microinjection of Plant Protection Products to Protect Apple Trees (Malus domestica) from Apple Rosy Aphid (Dysaphis plantaginea)

Conventional axial sprayers are poorly suited to orchards located in sensitive contexts (near water bodies, frequented by bystanders) or to large-volume trees. The result is often poor distribution within the canopy leading to more or less effective disease or insect control, off-target drift leading to environmental pollution and economic inefficiency. Trunk microinjection of plant protection products (PPPs) as a target-precise delivery system could greatly reduce the drift and improve the PPPs application. This study investigated the efficacy of five PPPs (flonicamid, spirotetramat, azadirachtin, lambda-cyhalothrin and deltamethrin) microinjected into the trunk of apple trees in 2022, 2023 and 2024 for managing Apple Rosy Aphid (Dysaphis plantaginea). Observations focused on aphid colonization and residue dynamics in buds, leaves and fruits. Under the conditions of the experiments, azadirachtin microinjection significantly reduced autumn infestation from 87 to 100% and spring infestation from 88 to 97%. The results obtained with flonicamid showed greater variability: from 50 to 80% fall infestation reduction and from 26 to 89% spring infestation reduction depending on the strategy and year. Spirotetramat and the two pyrethroids tested did not provide satisfactory control of populations. Residue levels varied by injected compound and the analyzed tissues. This study demonstrated that trunk microinjection could be an effective delivery method for existing PPPs, depending on the active ingredient, for controlling rosy apple aphids in orchards.