BRONZE BIRCH BORER

The Bronze Birch Borer is a insect that can infest, primarily, varieties of white birches. In its larval stage, the borer looks like white grub that is about three-fourths of an inch long. It tunnels just underneath the bark of the tree feeding on the living cambium layer. This tunneling results in feeding galleries which can, in effect, girdle the trunk and branches.

The first symptom of borer infestation appears in the leaves. Foliage near the top of the tree turns yellow and thins out. Swellings or raised ridges begin to appear on trunks and branches above the feeding galleries. Small "D"-shaped exit holes can be detected in late spring or summer. As the infestation becomes worse, branches and, eventually, trunks die off.

Borers are more likely to attack trees under stress than those that are healthy and vigorous. We make some specific recommendations about care and culture in our publication entitled "Birch Tree Care".

Schwarz Nursery recommends that purchasers of birch trees select either Whitespire or River Birch for inclusion in the residential landscape. Whitespire is more resistant to the borer than other white birch varieties; River Birch appears to be the most resistant birch cultivar.

An annual spring application of the systemic chemical Cygon is recommended, and this should be done around Memorial Day. Apply the undiluted Cygon in a 6-inch band around the circumference of each main trunk below the lowest horizontal layer of branches. CAUTION: Cygon, like many other pesticides, is a strong chemical. Keep children and pets away from the tree for at least a day or two after application. Refer to manufaturer's recommendations on the label, and carefully dispose of the brush or applicator used.