Leaves of butternut are often seen with large patches of
erineum, similar in general appearance to that caused by
Eriophyes erineus (Nalepa) on leaves of English walnut
{Juglans regia L.). The erineum growths are conspicuous on
the underside of the leaf blade, consisting of coalesced
patches of dense felted hairs lying alongside the midrib, usu-
ally filling the area between the lateral veins. On the upper
side, the leaf blade with erineum patches appears swollen and
puckered. The growth ranges from light brown to reddish
brown.

[photo pg. 113]

- Hartford Keifer,Edward Baker,Tokuwo Kono,Mercedes Delfinado,William Styer: (1982) An Illustrated Guide to Plant Abnormalities Caused by Eriophyid Mites in North America^©