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Protect Your Cherry Trees

Tree trunk borers will get them if you don’t watch out

While I was diagnosing why trees were dying at one Deale home, a neighbor complained of the loss of a flowering cherry. The tree had flowers very heavily last year, then died this spring.
    A quick examination of the dead trunk showed that tree trunk borers had killed the tree.
    Two different kinds of trunk borers attack cherry trees: the flat-head borer and the peach tree borer. Both borers prefer stems two or more inches in diameter. The peach-tree borer does most of its damage during the months of June and July, while the flat-head borer does most of its work in mid-August to mid-September.
    The entry holes made by the borers have a diameter approximately equal to that of the lead of a pencil. To the untrained eye, the holes are not noticeable.
    In a healthy tree, the entry holes created by both borers are marked by globs of reddish gummy resin, which prevents the borers from penetrating deeply. However, as the tree becomes weaker, its ability to produce the resin decreases.
    The year before the tree dies from borer damage, it will produce an extra-heavy load of flowers. This is because the many borer entries prevent some of the food manufactured by the leaves from reaching the roots. The result of this blockage in the stems is a large accumulation of metabolites, resulting in heavy flower bud set.
    If you have flowering cherries in your yard, keep them healthy by not allowing the grass to grow under the drip-line of the branches. If you are going to mulch, use compost and not bark or wood chip mulch. Irrigate the tree well during periods of drought. Examine the large stems and tree trunk for small holes or globs of reddish resin. If either are visible, spray all stems two inches or thicker with a tree trunk borer spray. These materials are changing almost every year; ask your garden center for recommendations.

Ask Dr. Gouin your questions at frgouin@erols.com. All questions will appear in Bay Weekly. Please include your name and address.