Prunus rust mite

On cherry plum trees in Western Washington, look for upward-curled mature leaves with brown or bronze undersurfaces; young foliage may show small yellow spots followed by shothole damage. These tiny mites feed on leaf surfaces, and while damage is rarely severe on vigorous trees, young unsprayed specimens can show noticeable leaf deformation and chlorotic flecking. The mites are barely visible without magnification.

Rust mites are seldom a management concern on established trees. Maintain vigor through proper irrigation and avoid stress. On young trees with significant leaf damage, apply dormant oil in early spring to target overwintering mites. Chemical control is typically unnecessary on healthy plants.