The most common type of worm found around oak trees is the green worm. Kept in check these worms are not a significant problem; if the population is not controlled the infestation can range from mild to serious depending on the health of the oak tree. Understanding how to identify these worms and when to look for them will help control infestations when they occur.
Green worms have various types. Identifying marks include the number of legs, stripe patterns, behaviors and location or size of the nest. Nests can be found at various locations in the tree. Nests can be of various sizes and the number of nests can tell how large the infestation is. Research into the type of markings and behavior found can tell what type of green worm is in the tree.
Green worms are common to the continental United States. Green worms are found on hardwood trees such as oak.
The main threat of the green worm is defoliation. Green worms eat leaves and portions of leaves. Severe defoliation of a tree by green worms is rare but possible; usually this is from a large infestation of worms in a single tree. Viewing large or multiple nests in a single tree is an indication of the size of the infestation.
Green worms are found mainly between May and June but can remain active until August. Annual infestations can occur in a single tree up to a decade in length with single outbreaks lasting up to three years. Because of this time range treatment should be ongoing after first sighting an infestation.
There are no preventive measures for green worms. Most control methods of worms are initiated by nature in the way of various natural enemies. Birds and wasps feed on green worms and can eliminate most of the problem. Extensive problems are treated with standard insecticide during the active period of the year for the specific type of green worm.