Most people know about carpenter ants and carpenter bees, but how many have heard of a carpenterworm? We have had several cases of carpenterworms affecting our customers’ trees. Carpenterworms are common but is rarely seen in its larval form and the adult form is nocturnal. This pest is most common in riparian zones, however, they can also be found in landscape settings. Carpenterworms feed on deciduous trees including oak, birch, ash, black locust, elm, maple, willow, cottonwood, pecan, and some fruit trees. The two instances we found this last summer were both oak trees.

How to Identify Carpenterworm

Plant Health Care Carpenterworm
Red circles are carpenterworm holes in the base of an oak tree. Red arrow shows frass (sawdust) at the base of the tree.

The signs of carpenterworms include large holes up to 1/2in diameter with frass (sawdust) visible in and around the hole. The gallery is vertical except for the entrance of the hole. Larvae are found in the trunk and branches of the tree but we typically find them in the trunk. Look for signs in crevices, in the bark, or in branch crotches of the tree. The larvae itself is greenish white with a brown head 2-3 inches long when mature. The large moth is black and gray mottled coloration with a wingspan of 3in.

Damage and Control

PHC Carpenter Worm Emporia Topeka
Carpenterworm damage in an oak tree. Chap-stick tube for size reference.

Carpenterworm boring can cause extensive damage to branches if the infestation is high. Large limbs may be girdled and killed, while live limbs may be weakened, making them more susceptible to storm damage. The entire canopy may appear to be in decline if the worm is present in high numbers around the base of the tree. Carpenterworms are attracted to stressed trees and rarely attack healthy trees, therefore the best way to alleviate carpenterworm damage is to prevent it from happening by keeping your tree healthy. This means avoiding root damage and trunk damage from mowers and string trimmers, proper watering, proper planting, mulching, and general maintenance.

If it is too late for prevention, mechanical or biological control options are available. Kill the larvae by taking a piece of wire and probing the holes to rupture the caterpillar. A nematode (Steinernema feltiae or S. carpocapsae) can be purchased in a spray and injected into the carpenterworm holes. The nematodes kill the worms.

If you suspect carpenterworms or some other insect is in your tree contact us.

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