Ash trees can be protected with a chemical insecticide treatment. Treatment can happen as a preventative measure before trees are infested with EAB or if the infestation is caught in the early stage, affecting 30 percent or less of the canopy.
By the time ash trees show the signs and symptoms of EAB such as woodpecker activity, bark splits and crown dieback, treatment may not be an effective option. Trees showing more than 30 percent crown decline are not good candidates for treatment. Consider treating ash trees that are larger than 10” in diameter and in good physical condition.
Treatments are injected at the base of the trunk and trees must be re-treated every two years. The cost is based on the size of the tree to be treated and the overall number of trees being treated on the property. This is an ongoing cost, and research has indicated you can protect a tree for 20 years for the cost to remove and replace an ash tree.
Be sure they are a licensed pesticide applicator. The Minnesota Department of Agriculture tree care company checklist can help you determine the best tree care company for you.
If you opt to treat the trees yourself, be aware that the available chemical treatments at homeowner and garden centers are not concentrated enough to protect an ash tree with a diameter greater than 15” (48” circumference) and are not as effective when EAB populations are high like they are currently in Farmington. Soil-applied insecticides can get taken up by nearby flowering plants and kill pollinators. In addition, soil applied treatments should not be used within twenty-five feet of a storm drain or water resource such as a wetland, creek or lake.
