Holly (Ilex spp.)-Sooty Mold

PNW Plant Disease Image

Lower older leaves have sooty mold which is growing on the excrement from the small long white cottony scale insects.

PNW Plant Disease Image

Many black lower leaves on this holly tree.

Cause Fumago vagans, a nonpathogenic fungus that grows on the honeydew (excrement) of scale insects.

Symptoms A dark-green-to-black layer on the upper leaf surface.

Cultural control

  • Wipe off leaves if mold is on only a few branches.
  • Control scale insects. See the latest edition of the PNW Insect Management Handbook for current recommendations.

Reference Hughes, S.J. 1976. Sooty moulds. Mycologia 68:693-820.