Beech Wooly Aphids and Sooty Mold

Author: Pamm Cooper
Pamela.cooper@uconn.edu

Reviewer: Heather Peracchio, UConn Extension
Publication EXT201 | March 2026

DOI Pending

Introduction

During the fall wooly aphid activity may be found on beech and other hardwoods. Particularly on American beech in the Northeast, the native beech blight wooly aphid, Grylloprociphilus imbricator, may be found by the hundreds actively feeding on branches and twigs well into November. 

Wooly Aphid Indicators

The wooly aphid can be seen easily as leaves fall, because their bodies are covered with white filament. These aphids feed on newer woody tissue and not on the beech leaves. This aphid is found only on American beech (Fagus grandifolia).

A photo of a branch with orange leaves of an American Beech, with a white fuzzy material on the branch. The words "Copyright Pamm Cooper" are written in the bottom right corner.
Beech blight aphids on a branch of native American Beech (Pamm Cooper)

A closeup of the brown branch of an American Beech, with a white fuzzy material on it. The words "Copyright Pamm Cooper" are written in the bottom right corne
Beech blight aphids on a branch of native American Beech (Pamm Cooper)

To Control or Not Control

These aphids are nicknamed boogie woogie aphids for their dance-like movement, especially when they are alarmed, or it is windy. While they form large colonies and seemingly cover smaller branches, tree health has not been determined to be negatively affected to a point where control measures are needed. On smaller trees with less biomass and more tender branches, appropriate control products may be used, if damage seems severe.

Aphids and Sooty Mold

An indicator that these aphids are on a tree is the development of a singular sooty mold caused by the pathogen, Scorias spongiosa. This spongy black mold develops on honeydew excrement that drips down as it is excreted by the aphids feeding above. It can cover leaves with a thick, black fungal growth that can completely cover leaves and twigs, in some cases looking like a black version of Spanish moss. Sometimes large blobs of sooty mold, several inches long or thick, are found on the lower parts of infested trees. This mold is more an aesthetic issue than harmful to the tree, as leaves are ready to fall at that time of year.

A photo of a stick in the woods covered by a black substance. The words "Copyright Pamm Cooper" are written in the bottom right corner.
Leaves and twigs of American beech covered in sooty mold (Pamm Cooper)

A photo of a hand holding a small twig with a large mass of black material on it. There are other trees and snow on the ground in the background.
A glob of sooty mold on beech twig (Pamm Cooper)

Resources

Boggs, Joe (September 20, 2021) Beech Blight Aphids are Jitterbugging Across Ohio OSU.EDU Beech Blight Aphids are Jitterbugging Across Ohio | BYGL (osu.edu). 

Childs, R. (2016, October 26). Beech Blight Aphid. Center for Agriculture, Food, and the Environment. https://ag.umass.edu/landscape/fact-sheets/beech-blight-aphid

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