borer, which occurs throughout the eastern United States, is probably
the most destructive pest of established flowering dogwood trees.
Young trees may die completely and older trees may be left with
dead or dying branches. Damage by this insect severely limits the
success and attractiveness of dogwood.
trees show swollen, knotty, calloused or gall-like areas on the
trunk. Dogwood borer adults, which are clear-winged moths, make
irregular burrows under the bark on the trunk, especially at ground
level and around the base of limbs or at the edges of wounds or
scars on the bark. Fresh sawdust-like borings are usually present
on the bark near active borer sites. In young trees, the crown is
attacked, resulting in wilting and die-back.
overwinter as immature larvae (caterpillars) in tunnels under the
bark. Full-grown larvae are 25 mm (1 inch) long and white to cream
in color with reddish-brown heads. Larvae change to pupae during
spring and adults begin to emerge by early June.
borer adult (left) and caterpillar.
Photo by Dr. Jim Baker, North Carolina Extension Service
most abundant in July, though some emerge throughout the remainder
of the summer months. Adults are clear-winged moths, active during
daylight hours. They have blue-black bodies with a yellow stripe
on the second and fourth segments of their abdomen; the legs also
have yellow bands. The wings are narrow and transparent. Female
moths lay eggs on smooth or rough bark. On older trees, they lay
eggs in scars and rough areas of bark on the trunk and larger branches.
hatch in 8 to 10 days and wander around the bark until an opening
is found for their entry into the cambium; the larvae are unable
to chew through bark. Once inside, they are well protected and difficult
to control. Larvae feed in this protected area throughout most of
the year. One generation occurs each year.
prevalence of dogwood borers and the ease with which they penetrate
injured bark makes control difficult. Preventative control measures
physical injury to the tree by unnecessary cutting or bruising.
Be careful in use of mowers near the base of trees.
newly transplanted trees to protect against strong winds.
cases, wrapping the trunks of new trees will reduce egg-laying of
non-native dogwood varieties less susceptible to dogwood decline,
since trees affected by this disease are more likely to be attacked
by dogwood borers. See GreenShare Factsheet on Dogwood
Diseases for more information.
optimum growing conditions for trees and remove dead or cankered
branches in dry weather.
are difficult to control once the larvae have gained entry under
the bark of a tree or branch. A residual insecticide applied in
June may help reduce damage and reduce the number of adults which
lay eggs on host trees, but coverage of trees is often expensive
from the Delaware Cooperative Extension, 1999