Do Tiny White Worms Live in Trees?

Round-Headed Borers

• Round-headed borers mature into long-horned beetles, named for their long antennae and round bodies. They create holes and tunnels that match their shape, round or slightly oval. Most larvae have three small legs just behind the head and push digested wood fibers, called frass, out of their holes. The frass and dark sap stains are visible on the outside of the trunk, indicating infestation. Two common examples are the red-headed ash borer and twig girdler.

Flat-Headed Borers

• Flat-headed borers mature into beetles with short antennae called metallic wood borers for their metallic green, blue or bronze coloring. The larvae have a large flat head, bigger than the rest of their body. The holes and tunnels they create in trees are flat ovals, much wider than they are tall. Examples are the bronze birch borer and flat-headed apple-tree borer.

Bark Beetles

• Bark beetles tunnel just under the surface of the bark, leaving hidden trails at the surface of the wood. The larvae have no legs and leave large numbers of small exit holes, giving the appearance that buckshot has hit the tree. Sap flowing from the holes can create small masses that, mixed with frass, extend out from the tree. Examples include the southern pine beetle, ips engravers and the Asian ambrosia beetle.

Weevils and Caterpillars

• Weevils are beetles with a distinctive long snout. Few weevils are wood borers, and the larvae, rather than chewing out tunnels, will live in hollowed-out cavities under the bark. Wood-boring caterpillars include carpenter worms and clearwing borers. Carpenter worms live in a tree up to three years before maturing into large moths with spotted wings. Clearwing borers, like the peach-tree borer, develop into moths with clear wings that look superficially like wasps.

Insecticide Controls

• Insecticides are unable to reach worms inside the tree, so treatments are aimed at adult insects before they crawl under the bark. Always follow the instructions on a product label to see if it is permitted to use against a specific pest. Permethrin is used as a preventative spray to affect adults when they land on the tree, but few permethrin products are labeled for use against borers. Soil drench products, like imidicloprid and dinotefuran, are effective on a limited number of species.