An ash protected with a once a year systemic soil drench is treated every 12 months, ideally in the fall or early spring, year after year. Trunk injection follows a stricter limit, with holes drilled no more than once a year and in no more than two years in a row.

Why does emerald ash borer protection need repeating?

Because a systemic insecticide, one the tree carries through its own tissues, wears off. Systemic treatments stay effective for one to three years depending on the product, while emerald ash borer keeps laying eggs on healthy and stressed ash alike.

How often is a soil drench applied to an ash?

Once every 12 months. Each fall or early spring, Once A Year Insecticidal Drench w/Merit is mixed and poured at the base at 1 oz of concentrate for every inch of trunk circumference, measured at chest height, so protection is renewed before the growing season.

How many years does an ash need protection?

For as long as emerald ash borer is active in the area, because untreated ash in an infested area are expected to die within about 10 years and damage can keep increasing even with insecticide. An arborist can judge whether a tree is still a good candidate for treatment, as the ash fertilizer guide advises.

Frequently Asked Questions

How often can an ash be injected instead?

Once a year at most. Holes for the Multi Insect Killer Tree Injection Kit are drilled at the root flare, where the trunk widens at ground level, no more than once a year and in no more than two consecutive years.

How soon after the yearly drench is the ash protected?

After about 3 weeks. That is how long the roots normally take to carry the insecticide through the tree.

What happens if a yearly treatment is skipped?

The tree is left exposed. The drench protects for 12 months, so once that window closes the borers can attack again.

Is yearly treatment worth it for every ash?

Not always. Insecticides are typically considered only for high value trees in urban areas near an infestation.