We’ve been planning for EAB for almost a decade now, and have proactively starting our work before we’ve seen the pest on campus grounds.

The insect was discovered on the Middlebury Town Green in 2021 in a state monitored trap. EAB can fly anywhere from 100 yards to 1 mile per year based on Ash population density, and at this rate is probably already on Middlebury land, just not at a discoverable population size. Statewide, Ash make up about 10% of our forest population, and our tree canopy both on campus and on outside lands seem to match this, with considerable variation in some locations.

There are few options for control of EAB. Biological controls  have been introduced in the United States by the USDA, and these show some promise on an ecosystem scale, but reliance on these are not recommended in Urban or target locations. Chemical

Our plan for dealing with the EAB threat on campus has two primary approaches: treatment of Ash for preservation, and pre-emptive removal and replanting of other species.

Treatment options to exist for combating this pest. We are using trunk injections of Emamectin Benzoate, derived from a soil bacterium. This pesticide is injected into the root flare of the tree in late spring, and is effective for two years. We treat about 40 Ash, 20 per year. We chose the trees based upon location or health. Three spectacular trees on the north side of Forest Hall are preserved, as are most Ash in the two main quads in the center of campus. Other locations include a stretch of Porter Field Road next to the track, and the basketball court/ park west of the HMKL Dorm complex. Ash in those two locations are densely planted monocultures, with no room to plant replacements nearby.

For the injection to be effective, however, the tree needs to be healthy and vigorous. A sick tree will not take up the insecticide. Ash have many native pests and diseases, and our tough conditions here on campus means many of our trees struggle, including Ash. Therefore, most of our work is focused on removal and replanting. We are beginning with our highest risk trees-trees that when dying may fall on buildings, powerlines, or roads, interfering with emergency services. We’ve mapped and prioritized all of our ash, and have begun in 2023 with three major Ash that were overhanging Wright Theater.

Once the tree has been removed, the leaves and branches are chipped and either used as mulch in our landscape, or composted and brought back to our soils. The wood is either used for heating in our staff’s woodstoves, or brought to our woodchip supplier and returned for use in our biomass plant.

Replanting and replacing our urban tree canopy is a continual process, and we have a goal of planting two trees for every one removed. Mainly native species are planted, but with diversity as a main goal for our tree population, naturalized and proven introduced species may be used in some locations.