Various willows are commonly infested by eriophyids. The situation is rather complex because the taxonomy of both the mites and the galls is uncertain. The galls on different willows are usually distinguished by form, color, position, density, and texture. Aculops tetanothrix belongs to a complex of gallforming eriophyid species that induce galls on different willows; consequently, the galls are varied. The galls caused by A. tetanothrix are 2-3 mm in diameter, beadlike, and irregularly rounded. They are often coalesced and scattered randomly or clustered alongside the midrib and in between lateral veins on the upper surface of the leaf blade. They vary from yellowish green to pinkish or reddish brown and purple. The exterior of the gall may appear roughened and shiny or covered with fuzzy fine hairs as on pussy willow leaves. Galls may be so numerous that they cover the entire leaf blade.

Phytoptus sp. [tentatively assigned to A tetanothrix]

Willow, Mass. May. Elevated, irregular masses," single or compound; on upper side of leaf and more rarely below. Both positions on same leaf. Green or red according to host willow.

[Fritz et al report a higher prevalence of Aculops tetanothrix on Salix eriocephala than on Salix sericea or hybrids of Salix eriocephala and sericea]

[Barbour reports finding Aculops tetanothrix galls on Salix hookeriana planted in a common garden experiment in northern California]

?Eriophyes aenigma

Salix
Capsule or pocket galls, plant mites, spring and summer

A number of other capsule or pocket galls are produced by undescribed species of Eriophyes

Aculops tetanothrix
Bead-gall mite
[Page 217]

This mite induces irregularly rounded bead galls on both sides of leaves of several species of willow from Utah and Arizona to California.