Thursday, May 10, 2018

Trying to Save a Tree from Emerald Ash Borer

The ash tree (left) in my side yard
This spring when I walked my garden assessing the winter and storm damage from the past two years I noticed the D shaped exit holes that are the signs of Emerald Ash Borer infestation on the ash tree on the side of my house. I love that tree and want to save it. Fortunately, I noticed the infestation while there is still hope.

Over the past few years the woods covering the back 7 acres of my land had become infested with Emerald Ash Borer. I noticed the damage first the summer before last when I was cleaning out trash from the river. The trees in my wood cannot be saved, but maybe there is still hope for the big ash on the side of the house. I called an arborist at “SavATree” to see what could be done. Pesticides can be applied to individual trees to protect them against Emerald Ash Borer and reportedly can save an ornamental lawn tree. For the pesticides to work the trees must be healthy and have at least 30% of their leaf canopy remaining. There is more than that on my ash.

The Emerald Ash Borer was first found in Prince William County in 2010. In the following years it spread across the county. At this point many ash trees in the county show the symptoms of infestation; epicormic branching (water sprouts), canopy die back, woodpecker damage, and bark splits. To tell if you have Emerald Ash Borer in your trees look for the 1/8th inch diameter D shaped exit hole and larval galleries that are the signs of Emerald Ash Borer infestation.

According to the Forest Service, protocol in areas were groundwater is used for drinking water is for either emamectin benzoate or a specific formulation of imidacloprid to be injected directly into the base of the tree trunk. The insecticide is transported within the vascular system of the tree from the roots and trunk to the branches and leaves- if it works. This reduces hazards to groundwater and to other plants from drift and protects the applicator from exposure, and has less impact on beneficial insects and other non-target organisms (like me).

Imidacloprid is not particularly soluble in water. The pesticide profile presented in the Extension Toxicology Network Pesticide Information guide concluded there is generally not a high risk of groundwater contamination when products are used as directed and appropriate precautions are taken. Similarly, the Canadian Water Quality Guidelines for the Protection of Aquatic Life noted that when imidacloprid is used correctly, it does not characteristically leach into soil layers leaving the groundwater unimpacted.

Drilling through the outer bark of the ash tree creates a wound in the tree. The response of the tree to these wounds is affected by factors such as the size and depth of the hole and the health of the tree. In recent studies, the injury associated with drilling holes and injecting two insecticide products into trunks of ash trees was examined. In nearly all cases, ash trees that were relatively healthy and properly injected showed little evidence of damage. New, healthy wood was produced over the injection sites and there was no evidence of pathogen infection, decay, or other signs of serious injury.
The ash tree is very near my well head

These injections should take place in late spring when the canopy is full. That should be in a couple of weeks or so. It is reported by the Forest Service that tree injections are tolerated in healthy green ash trees, especially if treatments are applied once every two years, small volumes of product are injected, and injection holes are small and shallow. That is the plan.

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