WSU Extension

Hortsense

Linden(Tilia) : Leaf galls
(revision date: 6/11/2014)


Biology
Leaves of linden or basswood trees (Tilia sp.) may be infested by eriophyid mites. These tiny, worm-like or spindle-shaped mites feed on leaf tissues and cause galls to develop. Damage may appear on the upper or lower surface of leaves. Elongated, pimple-like galls (often called nail galls, nipple galls, or fingergalls) are most commonly seen on the upper leaf surface. They are slender, with a round or pointed tip. Generally about 1/5 to 1/2 inch long, these galls may be greenish-yellow, pinkish, red, or brown in color. These nail galls typically appear around June and mature by July-August. Some lindens develop felt-like masses of tiny hairs on the back of the leaf instead of the protruding nail galls. Known as erineum, this damage is also caused by eriophyid mites. The erineum may be yellow to brown in color, and the damaged areas may appear on the upper leaf surface as discolored patches. Eriophyid mites on linden do not cause serious injury to trees; the damage is mainly aesthetic.
Management Options

Non-Chemical Management
  • Hand-picking severely damaged leaves may improve the appearance of very small trees.
  • These leaf galls do not have a great impact on plant health. No management is needed.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images
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Caption: Leaf galls caused by linden gall mite
Photo by: J.R. Glass, WSU
Caption: Erineum on littleleaf linden caused by linden gall mite
Photo by: J.R. Glass, WSU
Caption: Leaf damage caused by linden gall mite
Photo by: M. Zubrik, Forest Research Inst, bugwood.org