EAB Insecticide Treatment

When applied correctly, insecticides can protect a healthy ash tree against EAB.  Insecticides used for EAB fall into one of two general categories:
  • Those available to homeowners, and
  • Those available only to certified arborists or professional pesticide applicators who are certified and licensed to handle regulated use insecticides.
To ensure protection against EAB, an insecticide must be applied for several years. Nobody knows yet exactly how long that could be for our area. Soil-applied insecticides available to homeowners must be applied once a year. Trunk-injection insecticides available to certified arborists and professional pesticide applicators can be applied every two to three years, depending on the insecticide.

Most insecticides available to homeowners are applied to the soil around the tree base, either diluted as a drench or as granules. One product is applied as a spray, either to the trunk bark or the leaves. But this product is not recommended because (a) adequate research on its effectiveness against EAB has not been carried out and (b) misapplication can result in airborne drift that poses health risks to the person spraying, to other people and pets exposed to it, and to any nearby surface water.

Research has found that soil-applied EAB insecticides available to homeowners, if applied correctly, can be effective for an ash tree with a trunk circumference up to 48 inches (measured at 4.5 feet above ground). An ash tree larger than that should be treated with an insecticide injected into the trunk of the tree by a certified arborist or professional pesticide applicator.

If Your Tree is Showing Signs of EAB

If you wish to treat an ash tree infested with EAB, insecticide treatment can work if the infestation is detected early enough. Insecticide treatment is not recommended for trees with greater than 50% canopy thinning. If your ash tree shows signs of an infestation and you want to treat it, contact a certified arborist to determine whether insecticide treatment is a viable option.
  1. Hire a Professional
  2. Homeowner Treatments
If you decide to hire a certified arborist or professional pesticide applicator to treat your ash tree for EAB, the City recommends getting two estimates. List of Area Certified Arborists

Here are some reasons why you should consider hiring a professional to treat your tree:

A professional can treat your ash tree with a trunk-injection EAB insecticide. This is widely considered the most effective way to protect an ash against EAB. The tree can more reliably disperse a trunk-injected insecticide than a soil-applied one to provide the needed, year-round, systemic protection against EAB on two fronts: (1) the larvae, which hatch from eggs laid by adult beetles and burrow inward to feed mostly on phloem cells, which conduct food manufactured by the leaves and (2) the adult beetles, which feed on ash leaves during the summer and then lay eggs and die.

Although the initial cost of professional treatment is more than that of applying an insecticide on your own, the long-term cost may turn out to be far less. Trunk-injected insecticides certified professionals have access to need to be applied only once every two or three years, depending on the insecticide. Soil-applied insecticides available to homeowners, on the other hand, must be applied every year. Homeowners can make costly mistakes that result in poor protection and leave an ash susceptible to attack by EAB. Possible mistakes include incorrectly measuring the trunk circumference of the tree (which determines the correct amount of insecticide to apply); applying insecticide too early or late in the year; applying insecticide to soil that is too dry or too wet; and applying the insecticide prior to a major rainstorm. Any ash tree incorrectly treated for EAB eventually will be attacked and die. A homeowner could then be faced with the additional expense of paying for the removal of a dying or dead tree.

Potential for Groundwater Contamination
An EAB insecticide injected to the trunk by a professional stays within the tree. It does not pose any potential threat to groundwater. In comparison, soil-applied insecticides available to homeowners can leach through soils to groundwater in certain situations. The most obvious case would be an over-application of insecticide into dry, sandy soil overlaying a shallow groundwater table. Ashes are common landscape trees in yards in Fitchburg, Madison, Oregon, and Verona, numbering well into the thousands. Over-application by homeowners and other property owners of soil-based insecticides, even of small amounts, throughout Fitchburg and surrounding areas could lead to their gradual buildup in groundwater supplies. Several homeowners in a neighborhood located over a shallow groundwater table treating ashes in their yards with soil-applied EAB insecticides each spring, over time, could inadvertently cause some contamination.