University of Connecticut

Dogwood Borer

The dogwood borer is one of the most serious pests of flowering dogwood in Connecticut. Very young trees are frequently killed and older ones are left reduced in vitality and with dead and dying branches. Other plants attacked by this insect include flowering cherry, apple, mountain ash, willow and oak.

Borer-infested trees begin to show swollen, knotty, calloused or gall-like areas on the trunk, just at or immediately below the ground surface or between the ground surface and the branches above. Injuries also occur at the union of the trunk and branches or smaller twigs and branches. Young dogwoods are attacked mostly at the crown.

Life History

The adult dogwood borers are clear-winged moths which begin emerging in late May and may continue to do so until September. They reach their greatest abundance during late June and July. The moths mate and the females lay their eggs on bark, usually near an injury. The eggs hatch and the larvae wander about until they find an opening in the bark, since they cannot chew through uninjured bark. Upon finding an opening, they tunnel into the cambium of the older bark. They are not known to feed in sapwood. Borers in various stages of development can be found at the edge of bark wounds throughout the year. The larvae over winter in the tree and usually pupate there before emerging the following spring.

Control Measures

It is important to maintain the best possible health and vigor of dogwoods by fertilizing, pruning and by watering during dry seasons. Maintaining a mulch layer around the plant to aid in keeping the soil cool and moist should help in keeping the plant healthy.

Avoid wounding the trunks and branches. Lawn mower and line trimmer injuries afford excellent places for borers to enter. Mulch around the base to avoid these injures.

A fine wire can be inserted into the entry hole and pushed up the feeding channel to kill the larva. Recent research has found that beneficial nematodes can be an effective control measure for the dogwood borer.

For pesticide recommendations, call UConn Home and Garden Education Center at 877-486-6271.

Originally written by: Milton G. Savos, Extension Entomologist Emeritus, University of Connecticut,

Revised by: Edmond L. Marrotte, Consumer Horticulturist, Department of Plant Science,

Revised by Carol Quish, UConn Home and Garden Education Center, 2005.

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate. The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.