Sour Cherry Tree Decline: Lichens, Borers, and Oozing Sap

A 10-year-old sour cherry tree near a wooden fence shows green growth on the bark, dead branches, and sap-oozing knots. The owner sprayed fungicide, but the problem worsened. Here's what's really happening.

The Green Growth: Lichens, Not Disease

The greenish coating on the trunk and fence is lichen—a symbiotic organism of fungus and algae. Lichens are harmless; they don't parasitize trees. Their presence actually indicates clean air. Do not attempt to kill them.

The Real Culprit: Peach Tree Borers

Dead branches and sap-oozing knots point to borer infestation, specifically peach tree borer or lesser peach tree borer. These insects attack the upper trunk and branches of cherry, plum, and peach trees.

Identification & Life Cycle

• Larvae: White with brown heads, ½–¾ inch long.
• Adults: Metallic blue-black with pale yellow abdominal markings.
• Cycle: Larvae overwinter in bark, feed in spring, adults lay eggs in summer/fall. One generation per year.

Control Measures

• Timing: Treat in September–October or April for best results.
• Homeowner option: Bayer Advanced Garden Tree & Shrub Insect Control (imidacloprid) applied as a soil drench.
• Professional help: Contact a certified arborist for additional treatment options.

Always read and follow pesticide labels carefully. With timely intervention, the tree can often be saved.