A relentlessly-destructive pest, the Emerald Ash Borer (EAB), is killing ash trees in the eastern half of the United States and is spreading to the west. Sadly, this pest has forced homeowners to remove millions of dead or dying ash trees, while many still must make decisions on how to cope with infestations.

Ash trees are extremely common in yards and along streets throughout the country. The EAB, which kills all 16 U.S. native ash species, originally arrived from China to the Detroit area in 2002. As of 2015, reports of the beetle had spread to most Midwestern and east coast states and west to Colorado. Researchers expect the beetles will kill nearly all ash trees wherever their infestations spread.

These pests, which are dark green in color, are approximately ½-inch long and 1/8-inch wide as adults. They kill a tree when the larvae of the beetle bore under the bark, creating tunnels as they eat and slicing through the channels that transport water from the tree’s roots to the leaves. Once infested, unable to take up water, the tree dries out and dies.

What should you do if you live in an area infested by EAB?  First, identify if any of your trees are ashes.   If so, you have some decisions to make.

  • Consider protecting prime trees. One option is to try to protect the tree by treating it with a systemic insecticide that will destroy the borers when they eat the wood. Only certain insecticides are likely to hold off the borers. The product will need to be applied every year or two indefinitely, depending on the formula, the size of the tree, and the method of application. Treating a tree to deter EAB will become a yearly expense, but it may be worth it for an especially large, well-shaped tree that brings beauty, shade and value to a yard. It’s important, however, to start treatment while the tree is still healthy; insecticides will not save a tree that has already been significantly damaged by the borers. You should consult an arborist, a tree-care expert, to assess the condition of a tree before deciding whether to try to protect it. 
  • Wait for trees to die. Some homeowners decide not to treat ash trees. Instead, they replace the trees once the borers have killed them. An infested tree may take one year or several years to die, depending on a variety of factors including the amount of rainfall and the tree’s condition. Dead trees should be removed promptly as they can quickly become a hazard. The trees die by drying out and their wood becomes brittle; branches and entire trees break and fall. Some municipalities levy fines if trees are left standing.
  • Or give up on ashes. Another option is to cut down an ash tree in a heavily infested area even before it shows signs of damage. That way, you can plant a new tree—not an ash—and begin watching it grow and enjoying it instead of waiting for the inevitable destruction of the ash tree.

If you have an ash tree, it’s best to call in a landscape professional or arborist to discuss your options as soon as EAB is reported in your area. Having good information will help you decide on a strategy and plan for the expense of treatment or removal.

EAB is the most destructive forest pest ever to live on American soil.  Researchers are exploring how to fight against the infestations and the damage caused by the pest but in the meantime, homeowners with ash trees should be on alert and understand the problems they can expect if EAB take up residence in their communities.

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