University of Maryland Extension

Borers - Trees

clearwing borer gummosis on cherry
Gummosis from peach tree borer infestation

Key Points

  • Many different species of borers attack trees and shrubs.
  • They may be beetles or caterpillars (clearwing borers). Beetle borers include bark beetles, long horned beetles (locust borer) or round headed borers (red headed ash borer larva), and metallic wood borers (bronze birch borer or flatheaded appletree borer) or flatheaded borers.
  • Beetle borers usually only attack stressed trees. Symptoms include branch dieback and exit holes. Healthy trees are usually not attacked. The best control for beetle borers is to keep trees healthy and well watered.
  • No sprays are effective for control.

Emerald ash borer

Clearwing borers

They are the larvae or caterpillars of clearwing moths. The moths resemble wasps in appearance. Common examples are peach tree, lesser peach tree, dogwood, lilac, and ash tree borer. Larvae of these borers are creamy colored with brown heads. Signs of damage include holes in the bark, reddish frass in bark crevices or around the bottom of the tree and branch dieback. In the case of peach tree and lesser peach tree borer in flowering cherries, gummosis may be present. 

Management

To help prevent borers, especially in Prunus (cherry, plum), keep mulch away from the base of the tree. Keep trees well watered during dry periods. Avoid wounding the trees, especially with lawn mowers and string trimmers. Beneficial nematodes may be used to control these caterpillar borers as long as there is no gummosis. Follow package directions and spray in the evening.

peach tree borer damagepeach tree borer adult
Signs of damage from clearwing          Adult peach tree borer
borers (peach tree borer) include
holes in the bark, reddish frass in
bark crevices or around the bottom
of the tree and branch dieback

peach tree borer larvaash borer adult
Peach tree borer larva. All clearwing    Ash tree borer
borer 
larvae look very similar

bronze birch borer with exit holebronze birch borer
Birch borer and "D" shaped exit      Bronze birch borer larvae with frass
hole

bronze birch borer hole
D- shaped exit hole made by bronze
birch borer

Carpenter worm larva and damage.
Carpenterworm caterpillar and damage

dogwood borer adultflathead apple borer
Dogwood borer and pupal case           Flatheaded appletree borer

locust borer
Locust borer

 Rev. 2020

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