Woolly Beech Aphids: White Fluff, Honeydew, and Sooty Mold

In SE PA, beech trees have white fluffy coating on branches, sticky discharge killing undergrowth, staining ground, attracting bees. Owner asks if it's insects, mites, or fungus.

Diagnosis: Woolly Beech Aphids

Pale yellow aphids covered in waxy wool form dense colonies on shoots and leaf undersides. Honeydew drips, feeding sooty mold and attracting wasps/ants.

Impact

• Large trees tolerate heavy populations with little injury.
• Cosmetic: distorted tips, sooty mold, sticky surfaces.
• Photosynthesis reduced if mold covers leaves extensively.

Control (if desired)

• Hard water spray dislodges aphids.
• Insecticides: acephate (Orthene), imidacloprid (Merit), insecticidal soap.
• Systemic soil drench (imidacloprid) best for large trees.

Often no treatment needed; natural enemies regulate populations.