If there are borers in a tree or shrub, you will rarely see them. Borers are the larval, or worm stage, of many kinds of beetles and moths. They range in length from 1/2 inch to more than 2 inches. Usually they are white or pink with brown heads. Different borer insect species specialize in certain plants, laying eggs at different times and often several times a season. Consequently they may be active somewhere in your yard throughout the year. They feed on tissues inside the branches, roots, trunks and stems of all kinds of plants.
Borers burrow into target plants, forming tunnels inside their trunks and stems, where they live during this stage of their lives. The only visible signs of borers are small holes in tree or shrub bark and maybe some telltale sawdust, or frass, accumulated around the outside of the holes. Borer damage from tunneling weakens trees and shrub branches and drains plant vigor. Borers sometimes introduce diseases. Most woody plants are potentially vulnerable to one sort of borer or another.
Their Growth Stages
Eggs deposited on or just under the outer bark or stem surfaces by adult beetles or moths typically hatch tiny strong-jawed worms. They promptly burrow inside the plant stalks or the trunk wood and lurk beyond the reach of pesticide sprays. Typically, these worms pupate (go into a cocoon stage) in the plant or the ground near the plant before emerging in the spring as adult insects or moths to start the cycle all over again. Many wood-boring species require 2 to 3 years to fully develop into adults.
Some Common Borers
In the buttons on the left we have offered some brief descriptions of some of the most common borers found in the home landscape. The treatment for all these pests is the same which is described later in this file on Solutions.