Woolly elm aphid

The woolly elm aphid (Eriosoma americanum) is an aphid native to North America, found where Saskatoon (Amelanchier alnifolia) and American (Ulmus americana) elm trees are established.

Woolly elm aphid
Several young adult woolly elm aphids emerging from wool, with multiple undeveloped white round eggs present
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hemiptera
Suborder:	Sternorrhyncha
Family:	Aphididae
Subfamily:	Eriosomatinae
Genus:	Eriosoma
Species:	E. americanum
Binomial name
Eriosoma americanum (C.V.Riley, 1879)

Elm leaf infested with woolly elm aphids in different stages of development

The aphid feeds on the Saskatoon elm in late spring through fall, and the American elm during both early spring and late fall.[1]

Symptoms of American elm infestations include curled elm leaves, later accompanied by masses of visible dark areas and cottony masses. As with other aphids, honeydew may be found on infected leaves, excreted by the aphids after feeding on the plant's sap.

American elm leaves with woolly elm aphid infestation. Curled elm leaves are characteristic of the effects of the aphids, even prior to cottony masses being apparent.