Locust borers are black, long-horned beetles with bright
yellow bands across the body. The legs and antennae are reddish yellow.
These beetles are about 3.4 inch long. There is no description of the eggs,
but the immature stage is a plump, white grub with six tiny legs near the
head. The grubs grow to about 1 inch long.
Locust borers are found throughout the United States, and black locust
is the only host tree. Locust borers damage black locust by boring into
the inner bark and later into the heart wood. Heavily infested trees break
apart due to extensive tunnels in the heart wood. Trees growing on poor
sites are especially susceptible to locust borer infestations.
Adult locust borers feed on pollen and are often common on the flowers of goldenrod
in August and September. Females lay eggs in crevices of the bark and around
wounds. Newly hatched larvae tunnel into the inner bark where they spend the
winter. Growth resumes in the spring and the grubs begin to tunnel into the
heart wood . The larvae maintain openings to the outside through which they
push granular frass (waste products). There is one generation per year. Locust
borers tend to attack black locust trees that are young or under stress. Healthy,
dominant trees are often unaffected.
Spray trunks and larger limbs with a pesticide from the table below. The
first application should be made about mid August and a second 2 or 3 weeks
later. Insecticides are generally not very effective, however.
If the borers are already inside a tree, fumigate using aromatic solvent
such as fingernail polish remover. Put the solvent into an oiler or some
device that will squirt the solvent into the grub holes. After fumigation,
sealing the tunnels with wax or putty helps to hold in the fumes.
Remove and destroy badly infested trees in late fall or early spring.
Select a good site for black locust trees and keep them healthy.
Do not allow livestock to graze in locust plantings.
Locust borer not specifically mentioned on label. See label for sites
and application information. Not currently labelled for nursery use. Use
other permethrin product.
(Merit & others)
Imidacloprid has been found helpful in reducing impact of other longhorned beetles. It can be applied as a soil drench at the base of the tree or possibly as a trunk injection. (Imicide)
(Dursban Pro, Pageant)
Not for use on or near residential. 22.2% emulsifiable concentrate
50% wettable powder or water soluble granular
* Home owners may find permethrin containing products available in stores. Check label for "borer" recommendations.
For assistance with a specific problem, contact your local North Carolina
Cooperative Extension Service personnel.
Published by North Carolina Cooperative Extension Service Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people regardless
of race, color, national origin, sex, age, or disability. North Carolina
State University at Raleigh, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating.