NC State Extension Publications

Description and Biology

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Redheaded ash borers, Neoclytus acuminatus, breed in newly planted living trees and dying or dead hardwood trees and even felled logs that still have the bark intact (debarked logs are safe from this beetle). These relatively slender beetles are 1/2 to 5/8 inch long and have reddish heads and thoraces. The wings are dark and are crossed by four narrow, yellow bands. The two middle bands are chevron-shaped. The middle and hind legs are noticeably long and reddish. The antennae are about half as long as the body. The grubs are pale and legless and eventually grow to almost 1 inch long. This insect spends the winter inside a host tree probably in the pupal stage. Adult beetles emerge as the weather warms up in spring and are active until the weather cools off in autumn. Females chew notches in bark and lay their eggs under the bark. The newly hatched grubs feed on the sapwood and later tunnel into the heartwood and may turn the heartwood almost completely into powder. We have two or three generations per year in North Carolina. These borers may emerge from firewood kept indoors. There they are harmless but can be a nuisance.

Redheaded ash borer

Redheaded ash borers have four yellow bands across their wings.

Redheaded ash borer grub

Redheaded ash borer grubs are pale, legless, and slender when mature.

Redheaded ash borers pupa

Redheaded ash borers pupate in their tunnels.

Host Plants

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Redheaded ash borers can attack nearly all dying and dead hardwoods, but seem to prefer ash, hackberry, hickory, oak, and persimmon. Fruit trees and even grape vines may be attacked. Unseasoned logs of ash, hickory, and oak with the bark intact are especially attractive. In saplings, the larvae work in the inner bark and summer wood both horizontally and vertically through the trunk. Infested trees may break off during high winds.

Young redheaded ash borer grubs tunnel just beneath the bark.

Young redheaded ash borer grubs tunnel just beneath the bark.

New redheaded ash borer adults emerge through round holes.

New redheaded ash borer adults emerge through round holes.

Residential Recommendations

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There is no control recommended for redheaded ash borer larvae already inside living trees. Permethrin or another pyrethroid can be used to prevent further infestation by this pest if an infested tree is still sufficiently alive to try to save. Not much more that can be done other than pruning out dead and dying branches, mulch, water during dry spells, and perhaps fertilizing and liming ACCORDING TO A SOIL TEST. Fertilizer should not be applied without guidance as too much nitrogen can make trees even more attractive to borers. For example, redheaded ash borers are sometimes pests in young nursery stock where the saplings receive plenty of water and nitrogen.

References

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For assistance with a specific problem, contact your local Cooperative Extension center.

This factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology & Plant Pathology

Publication date: Sept. 29, 2017
Revised: Oct. 11, 2019

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