Did you know it is almost impossible to tell if a tree has Emerald Ash Borer (EAB) when the population is low in the tree? Symptoms usually do not appear until
years later, after the insect has become established in the tree. With Kenosha, Racine and Milwaukee counties under quarantine, your ash trees could be at risk.
Now is the time to protect your trees from EAB.
||There are two systemic insecticides that have shown to provide up to 90% or more control for EAB, emamectin benzoate and
imidacloprid. The first insecticide, emamectin benzoate, is a relatively new insecticide compared to imidacloprid and comes
under the trade names of TreeAge and ArborMectin. These products work great when there is borer activity in the tree. Both
products are injected into the tree by drilling numerous holes in the trunk around the base. But, the ArborMectin requires a
smaller hole, 15/64”, compared to TreeAge which needs a 3/8” hole. The down side of any injection is it wounds the tree which
could become pathways for other ash pests in addition to causing damage to the water and nutrient conducting system of the tree.
| The second insecticide is imidacloprid which is the most widely tested soil-applied insecticide for the control of EAB.
Because it is injected into the soil, within 18” of the trunk, there is no damage to the tree. Imidacloprid is best used as a
preventative, before EAB is established in the tree. To be effective, the insecticide needs to be applied annually. Another
imidacloprid treatment option is a Mauget trunk injection, however, this method requires drilling numerous 5/16” holes in the
trunk at the base of the tree, and once again, the disadvantage is wounding the tree. As with the soil applied imidacloprid, the
Mauget needs to be done annually.
Of course there are other treatment options available; however, they are not as effective. Basal trunk sprays require spraying the lower 5’ of the trunk
with a systemic insecticide. However, the basal trunk spray needs to be done annually and there will only be 50% to 70% control. Protective cover sprays, which
require spraying the entire tree with an insecticide, are the only treatment that targets the adult beetle and is the least effective. Because EAB is upon us, treatment
to help protect your high value ash trees should be done now. When deciding on a treatment option, think of the purpose of the treatment, the efficacy of the product
and the long term damage to the tree. There may be situations where you may only be able to do a certain treatment. In those cases, the benefits may out way the negatives.