Black Leaves on Ornamental Pear: Sooty Mold from Aphids

An ornamental pear has black leaves. The owner fears the tree is dead and asks if it must be cut down.

Diagnosis

Scrape bark on a high twig: green underneath means the tree is alive. The black coating is sooty mold growing on honeydew excreted by aphids or other sucking insects.

Treatment

• Control the insects → sooty mold disappears.
• Systemic soil drench: imidacloprid (Bayer Advanced Tree & Shrub Insect Control) applied to root zone.
• Foliar sprays: acephate (Orthene), bifenthrin, malathion, etc.—difficult on large trees.

Do not cut the tree. Treat the insects; the mold will weather off.