boxelder pouchgall mite

Spring through fall

Boxelder

Boxelder pouchgall mite is 7 ⁄1000″ (180 microns) long, about as long as a human hair is wide, and 21 ⁄10000″ (55 microns) wide. The human eye cannot see particles smaller than 50 to 60 microns, so this mite is probably invisible to most people. It is most easily identified by the type of growth (gall) it produces and the plant species on which it is found.

Boxelder pouchgall mite is found exclusively on boxelder (Acer negundo). In the spring, the mite forms a hollow, dull tan or gray pocket on the under surface of the leaf. The pocket is covered with a mass of felty whitish hairs. On the upper surface, it appears as an irregular, blister-like bump. The galls are solitary, though there are usually many galls on a single leaf.

This is the only mite that causes bladder galls on boxelder leaves.