Green Worms on Oak Trees

Protect oak trees from green worms.

The green worm is the most common type of pest in oak trees. Left unchecked, these pests can range from mild annoyances to serious threats to your tree's health. Careful maintenance of your oak trees, and a sharp eye for these pests, is needed to protect them and keep them healthy.

Time Frame

You will see the most green worm activity at the end of spring to early summer, May through June, although activity into August is not uncommon. Depending on the pest, outbreaks may be an annual occurrence or can occur in time frames as long as a decade, with the outbreak itself lasting two or three years. This makes identifying the specific type in question important to choosing what types of control are needed.

Identification

To identify the type of green worn, you'll need to get a sample of one by trapping it in a clear container. Look for any unusual physical features about the worm: the number of legs, any distinct stripe pattern, any specific behaviors it may engage in. Finally, inspect your tree for the nest. Note where the nest is located in the tree, what it looks like, and how many there are. This should make finding which green worm is infesting your tree easy to find online.

Geography

Most green worms found on oak trees will occur across the continental United States. They are extremely common and aren't unusual to find on oaks or other hardwood trees. As climates change and animals are introduced to different areas, new types of green worms may appear.

Significance

The more dangerous pests to your tree are rarely green. Most likely any green worm you're seeing is a Linden Looper, a Fall Cankerworm, or a Spring Cankerworm. These worms eat the tree's foliage, leaving holes in the leaves, and have unsightly nests. While occasionally these pests can severely defoliate trees, such outbreaks are rare and take many worms. This doesn't mean you shouldn't keep an eye on the health of your tree, simply be aware of the problem and be ready to act if necessary.

Prevention/Solution

While there are no prevention options, most outbreaks of green worms are best controlled by Mother Nature. These caterpillars have many natural enemies, such as birds and wasps, which will take care of the problem for you. If you have a more extensive problem, consider spraying your tree with a standard insecticide. This can be found at any hardware store, especially during the summer months when these pests are at their most common.

References

• Mississippi State University: Details on Common Green Worms
• US.. Forest Service: More Information on the Cankerworms and Linden Looper