What Is Eating My Tree Trunk? How to Deal with Tree Borers

Tree-boring insects are a likely culprit when wondering what is eating your tree trunk. Many varieties of these pests exist, and nearly any type of tree can fall victim if the circumstances are right. Learn how to deal with tree-boring critters, discover tree-saving methods, and prevent insects' return.  

What Are Tree Borers, and Why Are They Eating My Tree Trunk?

Tree borers are highly destructive to trees and shrubs. Their larvae do most of the damage after adult insects start the process. Wood-boring insect species lay eggs inside the tree, and when the young are born, they eat the tree fibers under its bark until they emerge as adults. 

Tree borers are destructive because they tend to destroy the most crucial part of the tree directly under the bark. Another reason is their activity can go unnoticed until it's too late to save the tree or repair the damaged tree trunk.  

Types of Tree-Boring Insects

Dozens of insect species qualify as wood borers, and it often takes an expert to discern which precise type is infecting your tree. Here are a few of the most common types. 

Round-headed borers

Round-headed wood borers also go by the name of long-horned beetles and typically attack trees already suffering from other stressors. The larvae of these beetles do damage by consuming the inner bark of limbs, trunks, and roots. 

Flat-headed borers

Flat-headed borers are similar to round-headed relatives in that their larvae consume the tree's flesh directly underneath the bark. Flat-headed species often have an iridescent appearance, giving them their alternate name, metallic wood borers. 

Moths

Clear-winged moths that look like wasps and other moth varieties are wood borers that generally attack specific types of trees in various conditions depending on the species. While the adults are harmless to trees, the larvae cause damage quickly.

Wood wasps

As the name implies, wood wasps are simply wasps that develop nests under the bark or into the flesh of distressed trees, from which their larvae consume the delicate fibers for up to two years before emerging as adults. 

Carpenter ants

Carpenter ants are somewhat different from other wood borers. While destructive when they attack cut wood in homes, finding carpenter ants in a living tree isn't always cause for alarm. Ants don't eat wood. Instead, they remove dead portions of it to make room for nests. Carpenter ants won't harm healthy tree parts. Their only interest is getting dead tree material out of their way.

How to Identify Tree Borer Activity

Identifying tree borer activity is quite different from diagnosing tree fungus types. Instead of looking for evidence in the leaves and dying branches, discovering tree borer presence is a matter of noticing signs in and around the tree's trunk. 

Adult insects must make their way deep into the tree's bark. This activity can create small amounts of sawdust-like material around the tree's base. Another word for the sawdust-like stuff is frass, which can serve as a first sign of trouble. The next signs of infestation are finding small oval or round holes where larvae emerge from after doing their damage and becoming adults. These holes may leak sap or oozing substances. 

How to Get Rid of Tree Borers

Success in eliminating tree borers can depend on how soon you discover the situation. If the tree isn't too far gone, there are several steps you can take to save the tree.  

1. Use Pesticides

Several types of pesticides exist that can treat or eliminate wood borers in the early stages of infestation. However, the use of some of these chemicals is highly regulated and only available to professional exterminators or arborists. Pesticides can be effective by applying them to the tree or surrounding soil, but you’ll need to hire a professional exterminator to do so.

2. Prune the Tree

In some cases, tree-boring insects may primarily attack tree branches. If that's the case with your tree, strategic tree pruning and trimming can reduce or eliminate the pests, slowing or stopping the damage. Be sure to consult a tree trimming specialist about the best pruning methods to use to avoid further damage or disturbances to the tree.

3. Use Manual Methods 

In some infestations, especially with moths that create relatively large holes for laying their eggs, you can insert a stiff wire into each hole made by an adult and kill the larvae hidden within. While tedious, this method avoids the use of chemicals or tree cutting.  

4. Replace the Tree

All too often, by the time tree-borer infestations make themselves known, the damage is too much for the tree to handle. Homeowners must frequently kill the tree and remove it if its death is imminent. 

How to Prevent Tree Borer Damage

While there are several ways to manage tree borers, prevention is the best method of protecting your trees. Try these prevention methods to help keep these destructive insects away. 

• Mulch and fertilize around tees and maintain proper seasonal watering schedules for the species.

• Consider regular preventative chemical treatments.

• Avoid pruning or trimming your trees when adult wood-boring insects are active and breeding. 

• Maintain healthy trees and protect them from injuries.

DIY Tree-Borer Management vs. Hiring a Pro

Controlling or getting rid of wood borers once your tree suffers an infestation is difficult at best. While DIY options for managing or eliminating the problem are available in the form of pesticides or manual removal, an expert's touch is almost always necessary. 

Your local tree maintenance professional can identify the infesting insects to develop and implement a plan to give your tree the best survival chance. Your professional can also offer other services that are tricky to DIY, such as straightening a leaning tree or providing a tree removal cost estimate if that becomes necessary.