The Town of Williston has created a plan preparing for the arrival of the Emerald Ash Borer, which will be referred to as the EAB from here on.  Links to the official plan and ash tree inventory are available at the bottom of this site, and a summarization of the different sections of the preparedness plan is provided below.

Purpose

The EAB preparedness plan was developed with assistance from the Williston Conservation Commission, Town of Williston Public Works, Chittenden County Forester, and the Vermont Departments of Forests, Parks, and Recreation.  The purpose of the EAB preparedness plan is to mitigate the effects of the pest when it arrives in Williston.  This involves addressing public safety concerns and minimizing the impact on the towns’ budget and public works manpower.

Emerald Ash Borer Background Information

The EAB is a half-inch long, bullet-shaped, metallic green beetle that feeds on ash trees.  Adult beetles lay their eggs on the ash trees, and upon hatching their larvae tunnel through the bark and into the cambium, eventually feeding on the phloem, a vital part of the trees circulatory system.  This attack on the trees circulatory system can kill it in as little as 2-5 years.  This insect is native to Asia, where ash trees have co evolved with it, thereby allowing the trees to build a resistance to the bug.  In North America the ash trees have no genetic resistance to the insect, and this is why the mortality rate for infected trees is almost 100%. 

The EAB was first discovered in the United States in Southeastern Michigan in 2002 and has since spread to 22 states and 2 provinces, killing 150-200 million ash trees in the process. Though not yet discovered in Vermont, EAB infestations have been confirmed North, South, East and West of Vermont in Concord, NH, Dalton, MA, Albany, NY, and just 30 miles North of the Vermont border in Quebec.  For this reason it is not a matter of if the EAB reaches Vermont, but rather when it reaches Vermont. Williston is at a particularly high risk of impacts from the EAB as 43% of publicly owned trees and 51% of street trees in Williston are ash, with some neighborhoods such as Wildflower Circle and Harvest Lane consisting of over 90% ash.

Identifying Signs of Infestation

To identify infected ash trees it is first important to be able to identify ash trees.  Ash trees can be identified by their compound leaves, opposite branching pattern, and tight bark with diamond-shaped ridges. 

Very early signs of infestation are difficult to detect, but the earliest visible sign is increased woodpecker foraging.  The first easily detectable signs are dieback in the upper canopy of the tree, cracking bark, and new growth sprouting at the base of the tree.  D-shaped exit holes and serpentine under-bark galleries are also telltale signs of infestation.  Infested trees will lose foliage from the top down until they are unable to produce leaves. 

Management Strategies

Ash Tree Removal

Ash tree removal can be done two ways, either proactively or reactively.  As with many management strategies there are positives and negatives to both.

The proactive removal of trees is often used as a way to prepare for the EAB especially in towns with a large number of ash trees.  The reason for this is that when the EAB arrives it could kill almost all of the ash trees in an area within 4 years, creating a massive burden on a towns budget and manpower as they are forced to remove hundreds of dead ash trees that are not only unsightly but also pose a public health hazard as they rot and become unstable. 

The reactive removal of trees can cause towns to run into the budget and manpower issues that the proactive strategy avoids, but the upside is that it allows for the healthy ash trees to be enjoyed for their aesthetic and ecosystem services value for as long as possible.  An additional concern involving the removal of dead ash trees is that the nature of cutting dead wood, including the unpredictable nature of the wood and the added strain on equipment makes it more expensive than live tree removal.

Preventative Treatment

It is possible to save ash trees from the EAB by biannual insecticide injections into the tree.  These injections must be done before the EAB is present as they rely on the trees circulatory system being healthy.  These treatments are expensive however, and that is why they are often reserved for trees that are particularly important for cultural or aesthetic reasons.

Williston’s Ash Management Plan

The management plan in Williston uses each of the techniques mentioned above.  It is currently planned to conduct proactive cutting of trees within the town right-of-way.  This plan will allow for ten percent of the towns ash trees within the right of way to be removed within ten years of the start of the plan.  The trees will be replaced with a variety of species to increase the diversity of Williston’s tree population so that this situation might be avoided in the future should another species specific pest or disease emerge.

Preventative treatment is planned for the large trees on public property near the town library.  These trees are impressively large and beautiful and serve as excellent specimen trees to be preserved.  This treatment will begin prior to the EABs arrival.

Ash trees in town parks and on conserved lands will be left alone.  As the trees die during the infestation they will fall naturally and decompose.  Trees near public paths will be monitored and if the become a danger to the public they will be removed. 

Williston Ash Inventory