gummosis from borer insects in cherry tree

Sap and gummosis on a cherry tree trunk, symptoms of a borer infestation. Photo: Ellen Hartranft

Updated: February 28, 2023

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

emerald ash borer adult
Emerald ash borer adult. Photo: Debbie Miller, USDA Forest Service,

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. 

peach tree borer insect
Peachtree borer (Synanthedon exitiosa). Photo: Joseph Berger,
peachtree borer larvae
Lesser peachtree borer larvae. Photo: Clemson University - USDA Cooperative Extension Slide Series ,


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.

Rev. 2020