Q I saw a billboard along a road directing me to a website to arrange for treating ash trees to prevent emerald ash borer. Is this a good idea? Should ash trees be treated now to prevent infestations?
A Before deciding to treat a tree, the Minnesota Department of Agriculture (MDA) suggests that you ask yourself these questions:
Is it an ash? It sounds strange, but some trees can be mistaken for ash. The emerald ash borer (EAB) attacks only ash trees.
Is it within 15 miles of a confirmed infestation? Hold off on treating any tree until there's a confirmed EAB infestation within 15 miles of your land.
Is it the right time? Timing matters. Insecticide chemicals need to be in the leaves before the adult EAB becomes active and feeds, which is June through August. That means mid to late spring is the best time to treat an ash tree. Treatment in mid to late autumn may not be as effective.
Is it worth it? Treatments cost $50 to $200 and, once you start them, must be done every year or two. Trees of high value, such as those providing critical shade or aesthetic value to a property, are the ones to treat. It would be better to remove smaller trees or those not of high value.
Be aware that some treatments are injected into the tree, while others are applied near the base. How effective any treatment is depends on what is used, how it's done, the age of the tree and how badly the tree is infested. Experts say that once it's more than 30 to 40 percent infested, the damage is so great that there's no way to save the tree.
"We aren't aware of any infested trees in Minnesota now," said Mike Schommer with the Minnesota Department of Agriculture. "The 67 infested trees found in St. Paul have been removed." He added that those trees had been infested for three to five years, so it's fairly likely there are other infested trees that haven't shown any symptoms yet.
