Bad Wood-Boring Insects

By: Anthony C. Arnoldi, Board Certified Master Arborist WI-0102B

Summer 2007 Newsletter in Adobe PDF format Most borer species attack weakened trees. Proper diagnosing and proper treatment are essential in their control.

Doctor Wayne Sinclair, one of the foremost plant pathologists, when presented with a sample from a sick tree that defied identification, exclaimed, “There’s something inherently evil in that tree!”

The same may be said of wood-boring insects. If anything “could cause fear in the hearts of trees and shrubs,” it would be this group of villains. Borers feed inside the trunks, branches, twigs or roots. Any plant part large enough to contain their bodies is susceptible to attack. Injury is usually long-lasting, with moderate to heavy infestations resulting in the death or disfigurement of the tree.

Every tree or shrub has borer species that attack it. Some are beetles, while others are moths or even flies. In every case, the larvae or “worm” does the actual damage. Over the course of their development, the damage created by eating their way through the wood and bark starts out small but soon becomes more serious as their bodies get larger. Most larvae are legless, whitish to yellowish in color, and are soft and fleshy. They spend from several months to two to three years in the tree, depending on the species. This is when frass, a mixture of sawdust and excrement, can often be seen coming from the bore holes.

Most borer species attack primarily weakened trees. The extended drought of the past 10+ years (now eased?) has been the main reason so many trees have become infested. The drought weakens tree defenses, and borers can then successfully finish their life cycle to adulthood. This has meant a large, growing population to attack more and more trees. When stresses continue, borers are able to attack more than just their “preferred” tree species list. They can then expand their attack on other trees. Conditions over the past several years have enabled all of this to happen. Borers have appeared on many sites. Oaks, maples, birches, honeylocusts, pines and crabapples are some of the worst hit species.

Borers can be controlled, if diagnosed early enough. In many cases, very specific materials and timing, used with consistency, will do it. If incorrect methods are used, control will be delayed or will not be effective in saving the tree. If your arborist has indicated a borer problem, then this needs to be a priority in decision-making, so that treatment or removal will prevent further injury.

Borers are not easy to control, and a competent Certified Arborist, with understanding of both the biology of the tree and pest, should evaluate the situation. Do not take chances with your valuable trees. Trust your Wachtel Certified Arborist to develop a management plan to protect them.

© Copyright 2007 – Wachtel Tree Science & Service, Inc.

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