Taphrina populisalicis

Taphrinaceae

Taphrina

Populus fremontii

Arizona

California

Idaho

Nevada

New Mexico

Texas

Utah

Populus trichocarpa

Taphrina populi-salicis

Causing golden-yellow convex-concave spots on leaves of Populus fremontii  [and] P. trichocarpa ...


A monograph of the genus Taphrina

Taphrina populisalicis
[Page 58]

Hosts: Populus balsamifera subsp trichocarpa, fremontii, Salix laevigata

Convex, light green bumps correspond to yellow depressions on the opposite side of the leaf.

Range: worldwide

Plant Galls of the Western United States

When Mix first described Taphrina populi-salicis in 1947, he listed Salix laevigata as a host. But in 1956 he concluded that the willow-like leaf that led to the "-salicis" part of the name was actually a Populus trichocarpa leaf -- possibly var. hastata--that was long and narrow and looked very much like willow.

See pg 468 of Mix, Notes on Some Species of Taphrina. Transactions of the Kansas Academy of Science (1903-), Vol. 59, No. 4 (Winter, 1956), pp. 465-482
https://www.jstor.org/stable/3626314. 

"The specific epithet of the fungus becomes an unfortunate misnomer," he wrote.

Gallformers ID Notes