Several kinds of woody plants in this area are subject to attack by borers. Young flowering dogwood trees are commonly killed by them, and older ones are reduced in vitality with dead and dying branches. Birch and peach trees also suffer severely from borer infestations. Now is the time to do something about them.
The adults of most kinds of borers are moths - the adult bronze birch borer is a beetle - that emerge in late spring and early summer over a period of two or three months. They lay eggs that hatch into borers (worms), which tunnel under the bark of trees. Once inside, they're hard to get at, and the following spring they emerge as adults.
Spraying the tree's bark at appropriate times may destroy the adults before they can lay eggs, or the young borers before they can do damage. Specialists recommend the use of endosulfan (Thiodan) or Methoxy chlor, but Thiodan should not be used on birch trees or where it can get on geraniums, some other flowers or Concord grape vines. It's important to read all the directions and warnings on the label and follows them closely. To be effective, springs must thoroughly wet the surface to be treated, or come into contact with the insects.
For dogwood borers, treat the trunk and main limbs in mid-may to late May, and again about a month later, for peach-tree borers, treat the trunk and soil around the base in late May and repeat at three-week intervals; for bronze birch borers, treat all bark surfaces, especially in the uppermost part of the tree, in mid-May, early in June and again in mid-to late June.
One thing borers have in common, according to Dr. John A. Davidson, University of Maryland extension entomologist, is their absolute preference for weakened plants.
Two or three years of low rainfall are often followed by large numbers of borers. Newly transplanted trees are especially susceptible to attack until they establish good root systems. Wrapping the trunks with heavy paper provides a lot of protection.
Young trees and shrubs grown in partial shade and moved into full sun may become vulnerable. Improper pruning, wounds caused by lawnmowers, wind damage, snow and ice injury - all provide attractive sites for the moths to lay eggs.
Heavy construction may change grades, alter water tabl es, compact soil and mechanically damage trees and shrubs. These result in stressed plants attractive to borers. High concentrations of air pollution from cars, salts applied to roads in winter, fumes from factories - all contribute to poor plant health and reduced vigor.