Borers In Ash

Just because the Emerald Ash Borer has not been found in your area, doesn’t mean you are in the clear of damage from Borers on Ash in your area.

Emerald Ash Borer is a wood-boring beetle that only feeds in the cambium layer, just inside the bark of the tree. Borers that feed in this area are killed by theuse of the Systemic Insect Drench.

Another borer common to Ash trees, in the long-horned beetle family of borers, is the Redheaded Ash Borer. Systemic Insect Drench does work on them as well.

Ash/Lilac Borer  is a wood-boring caterpillar. These caterpillars feed in the cambium layer, but they also feed in the sapwood and heartwood, migrating in and out. Since they do not only feed in the cambium layer, the Systemic Insect Drench, does not work.


Ash/Lilac Borers  are technically a clearwing moth that resembles a wasp. They are active from late-April through May, maybe even into June depending on your area and the season. One University says they appear about one week AFTER full bloom of: Lilac, Flowering Dogwood or Sargent Crab.

This is when you want to apply your first application of 38 Plus. Spray the lower branches and trunk and up to 6 foot around the base of the tree or lilac. Spraying the leaves offers NO protection.

Repeat application 3 weeks later. On these first two applications, use the higher rate of 4 teaspoons per gallon and use Spreader Sticker to improve coverage and adhesion.

When the infestation is bad, repeat again in 4 weeks at the lower rate of 2 teaspoons per gallon with Spreader Sticker.


On both Lilacs and Ash Trees this borer is attracted to; older canes, damaged areas and stressed plants. Maintain vigor with Tree & Shrub Food and use Pruning Seal on any damaged or pruned areas.

Immediately remove any dead or dying branches every year, these are what attract the adults to the plant.

Protective sprays will be required every year if an infestation has occurred.