Trunk Injection for Arthropod Pest Management in Woody Plants: A Comparative Perspective Under Greenhouse and Field Conditions

Woody plants in managed and natural ecosystems are increasingly exposed to arthropod pest pressure, posing challenges for sustainable plant protection. This study evaluates trunk injection as a pest management strategy in woody species, with emphasis on plant-mediated processes shaping interactions between host plants and herbivorous arthropods. Two experimental systems were investigated: a greenhouse experiment with Gleditsia triacanthos and a field experiment with Quercus petraea. Systemic active ingredients (acetamiprid and abamectin) were applied using both experimental and professional injection devices, and their effectiveness was assessed against Tetranychus urticae and a complex of foliar-feeding insects. In the greenhouse experiment, trunk injection reduced T. urticae populations compared with untreated controls and soil drench treatments, with reductions of 55.6–58.4% for larvae, 65.7–67.5% for eggs, and 28.7% for adults, although foliar application achieved higher suppression (up to 81.2% for eggs). In the field experiment, treatments reduced leaf discoloration (from 16.3% in control to 1.45–3.80%) and skeletonization (from 15.1% to 9.95–12.7%), with more moderate effects on defoliation. Differences among feeding guilds suggest that responses to systemically distributed compounds depend on feeding behavior and canopy position. Both pressurized and non-pressurized methods enabled uptake and translocation of active compounds within plant tissues. Localized injuries were observed at injection points, including internal necrosis. Overall, trunk injection represents a viable approach for pest management in woody plants, highlighting the role of plant-mediated processes in shaping treatment outcomes under contrasting conditions.