By Marcia Anderson
I was recently in a conference of certified tree experts to discuss the invasion and progressive devastation of our nation’s ash trees by a creature known as the emerald ash borer. While much of the country has already suffered the death of their ash trees, New England has time to react.
Think back. First, it was Dutch elm disease. Later, chestnut blight, the gypsy moth, followed by the Asian longhorn beetle. Now, the emerald ash borer is approaching and has already ravaged much of the nation. While common in cities across much of the US, native ash trees (Fraxnus sp.) have little natural resistance to this pest. In addition, the Asia native has no natural enemies in the US.
A major problem with an emerald ash borer infestation is that most people do not see it is coming, and by the time the trees show signs of decline, it is too late. Some 95 percent of ash trees hit with it will be dead within five years. The only way to save your favorite ash trees is to prepare.
Ground zero for the invasion was near Detroit in 2002. The borer has already swept through the midwest and devastated almost every ash tree in its path. It is now in 34 states and 2 Canadian provinces. It has not yet reached New England.
At the conference I attended in New Jersey Dr. Jason Graboski of Rutgers University said some parts of New England that are not yet affected can benefit from the lessons learned by Michigan, Ohio and Pennsylvania.
If trees are within 20 miles of an infestation, they are at risk. That is when to take action. By the time people notice thinning in the canopy, the borer has already caused considerable damage.
There are three options for managing urban ash trees: removal and replacement; treatment with insecticides until they can be removed; and treatment with insecticides for the duration of the infestation.
An Integrated Pest Management program reduces both pests and unnecessary pesticide use. This approach stresses monitoring, maintenance, and sanitation. But pesticides, when needed, can also be used. Treating for the borer falls into this “when-needed” category, in lieu of removing all ash trees. Even large ash trees can be protected by insecticides. Milwaukee, Wisc., saved most of its trees by using pesticides
The emerald ash borer attacks trees of all sizes, starting with large trees, devouring the insides of every ash tree in its path. It first attacks stressed trees. The females lay 30 or more eggs in the cracks of bark, which hatch leaving larvae that bore into and feed on the phloem that conducts nutrients throughout the tree. Gradually, the infestation moves into inner layers of the tree. The larvae spend one or two years feeding inside the tree before emerging as adults in spring. Once you see exit holes at eye-level, the infestation has probably been there several years. Symptoms that aid in early detection are yellowing leaves, loss of leaves or death in the canopy, and eventually a dying tree.
The borer is often found near highway rest stops. One once landed on my windshield at a rest stop. It was the first time I had seen one, and I marveled at its size and metallic green color. They easily hitchhike on trucks and rail cars so are commonly dispersed along railroad and other transportation thoroughfares.
New Jersey, New York, and the New England states are now the latest targets of this pest.
There are a few ways to prevent the spread of the borer. 1) First and foremost quarantine all ash wood, including firewood. 2) Replace all ash trees with a diameter of 12 inches or less even if it is not infested. If your community decides not to treat with pesticides, those ash trees will die, and become hazardous. You can remove them now or later at a higher cost. 3) Infected trees should all be removed, the largest first. The wood should then be chipped or kiln dried. Ash makes good pellets for wood burning stoves and can be used in furniture and baseball bats.
The important thing is to prepare ahead, before the emerald ash borer is already doing its deeds.
Marcia Anderson, who has a doctorate in environmental management, works with EPA’s headquarters on issues related to pest management in schools. She formerly worked in pesticides for EPA Region 2 and has a home in Lyman, Maine