The efficacy of trunk injections of emamectin benzoate and phosphorous acid for control of obliquebanded leafroller and apple scab on semi-dwarf apple

Abstract

Trunk injections reduce pesticide inputs and environmental contamination, and recent work has addressed apple production systems. Insecticides and fungicides have been demonstrated for apple tree injection, however combinations of the two have not yet been tested. Trunk injections of the systemic insecticide emamectin benzoate and systemic acquired resistance (SAR) fungicide phosphorous acid were performed on mature apple trees to combine management strategies for foliar insect pests and apple scab (Venturia inaequalis). Injections of emamectin benzoate followed by phosphorous acid into the same set of injection ports resulted in higher mortality of Choristoneura rosaceana larvae and lower incidence of apple scab compared to the control. Scab incidence on trees in which phosphorous acid was injected into the same set of ports before emamectin benzoate were not different from control trees early in the growing season. Injections of emamectin benzoate and phosphorous acid into the same holes in either order showed higher mortality and reduced larval feeding in C. rosaceana bioassays compared with products injected into separate holes. This study demonstrates that two pesticides can interact dynamically within the vascular system of a tree, which has important implications for expanding the utility of trunk injection for fruit tree management.