Physiological Response of Ash Trees, Fraxinus spp., Infested with Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), to Emamectin Benzoate (Tree-Äge) Stem Injections

Street- and park-planted ash (Fraxinus spp.) trees infested with emerald ash borer (Agrilus planipennis Fairmaire) ranging in size from 30 to 55 cm (11.8 to 21.7 in) dbh and 10 to 20 m (32.8 to 65.6 feet) in height were measured over two sites. The first group was treated with an emamectin benzoate stem injection at 10 ml/2.54 cm dbh (0.4 g ai) in June 2014, and the second group was left as an untreated control. Chlorophyll concentration and fluorescence was measured to assess plant fitness and vitality over three summers. Trees treated with emamectin benzoate showed improvements in chlorophyll concentration and plant fitness and vitality over the course of the study with peak improvement occurring in the second year. The untreated control trees showed continued signs of decline in each year of the study. This work demonstrates the utility of chlorophyll fluorescence for detecting plant stress related to forest health threats and could potentially inform managers on both short-term and long-term management options.