Sooty Mold on Beech

Question: What is this strange growth on my Beech tree? It starts out white and then turns a sooty black color.

Answer: The sponge-like growth on this branch and leaf collected from a beech tree is an unusual type of sooty mold. Sooty molds are entirely superficial saprophytes that get their nourishment from honeydew-like secretions from insects such as aphids, soft scale, and mealy bugs. The beech tree was infested with a woolly aphid species and thus this specific sooty mold fungus, known as Scorias spongiosa, is feeding on the honey dew excrement from the woolly aphid.

-Gail Ruhl, Senior Plant Disease Diagnostician, Interim P&PDL Director, Purdue University