To treat or not to treat: Diminishing effectiveness of emamectin benzoate tree injections in ash trees heavily infested by emerald ash borer
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Urban Forestry & Urban Greening
Emerald ash borer (EAB), a non-native invasive tree-boring beetle, is the primary agent behind thewidespread mortality of ash trees (Fraxinus spp.) in both natural forests and urban areas of North Amer-ica. While a variety of insecticide options have been adopted for protection against EAB attacks, little hasbeen reported on the success of insecticide treatments on EAB-infested trees. This is particularly impor-tant because EAB is difficult to detect in early stages of its infestation and protective treatment may beundertaken on trees already in decline. Here, we investigated the effectiveness over a four-year period ofbiennial emamectin benzoate injections in trees exhibiting different initial EAB infestation levels (esti-mated using visual ash canopy condition metrics) in an ash forest in central Ohio. Results indicate thatemamectin benzoate treated trees exhibited less canopy decline relative to non-treated control trees overthe course of the experiment. In fact, all untreated trees died over the course of the four-year experiment,while on average treated trees did not exhibit a significant decline. Furthermore, initially healthy andmoderately EAB impacted trees treated with insecticide either maintained or improved their canopy con-dition, while initially heavily EAB impacted trees stabilized, declined slightly, or died. Our results suggestthat by using trunk injections of emamectin benzoate, private and public landowners may effectively beable to preserve lightly or moderately EAB infested trees or delay the replacement of ash trees at varyinglevels of EAB infestation.
KeywordsCanopy decline; Fraxinus; Insecticide; Invasive species; Urban forestry
Flower, Charles E.; Dalton, Jennifer E.; Knight, Kathleen S.; Brikha, Marie; Gonzalez-Meler, Miquel A. 2015. To treat or not to treat: Diminishing effectiveness of emamectin benzoate tree injections in ash trees heavily infested by emerald ash borer. Urban Forestry & Urban Greening. 14(4): 790-795. https://doi.org/10.1016/j.ufug.2015.07.003.