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Posted 10 April 2009. PMN Crop News.

Pesticides Can Protect Valuable Trees from Emerald Ash Borer

Purdue University.

West Lafayette, Indiana (April 6, 2009)--Homeowners in or near areas infested with emerald ash borer can protect their ash trees from the invasive insect by applying pesticides in April.


If applied properly, these pesticides can protect healthy ash trees from emerald ash borer (EAB) infestation for an entire year.

"For healthy trees, pesticides provide effective protection against EAB," said Jodie Ellis, Purdue University entomologist. "For ash trees 45 inches in circumference or less, homeowners can purchase products at their local garden centers and do the application themselves."

Homeowners should use products in the form of a soil drench that contain a formulation of 1.47 percent imidacloprid.

"Pesticides sprayed on the tree leaves have little effect on EAB because EAB larvae, the immature wormlike stage of the insect, feed under the tree's bark," Ellis said. "Therefore, the goal is to distribute the pesticide under the bark so that feeding larvae will be killed. With a soil drench, the pesticide is mixed in a bucket with water and then poured around the base of the tree. The tree's roots uptake the chemical and spread it through its vascular system."

To mix and apply a soil drench, homeowners should follow label instructions based on the tree's circumference in inches. For healthy ash trees larger than 45 inches in circumference, not enough product gets beneath the bark to protect against emerald ash borer. In these situations, a professional arborist can protect the tree.

"Larger trees will need stronger formulations of pesticides injected directly into the tree," Ellis said. "A certified arborist will have access to both the special equipment and the pesticides necessary to provide effective EAB protection."

On smaller trees professionals can use imidacloprid, which should be applied annually. On larger trees they may use a newer product called emamectin benzoate, which can be applied every two years.

When determining whether or not a tree is a good candidate for protection, Ellis said there are a few signs to look for.

"Because of the cost and effort involved, it's not usually possible to protect all the ash trees in a wood lot," Ellis said. "But homeowners can protect individual ash trees that are valuable to their landscapes. These should be healthy trees that don't have thinning canopies or dead limbs."

As an alternative or supplement to treatment, homeowners whose trees are mostly ash might want to consider planting some different species, Ellis said.

"If you're in or near an area where EAB has been confirmed, replant your landscape with a different species before EAB kills off the ash," she said. "By the time the unprotected ash trees are dead there will be established trees in place to lessen the shock of losing the ash."

For more information on tree protection options and a list of replacement tree species, visit the Purdue emerald ash borer Web site at Questions also can be directed to Ellis at (765) 494-0822,

Jodie Ellis