Heavy infestations often give limbs a gray, encrusted appearance. Wood under infested bark often has reddish-purple spots or streaks where tissue has been killed. Infested trees exhibit a loss of vigor, terminal die-back, and eventually die if the scale is not controlled. The Forbes Scale resembles the San Jose Scale in appearance and damage. Leaves are skeletonized, folded and webbed together.
Fruits are shallowly scarred, especially where they are in contact with infested leaves.
The rosy apple aphid is purplish or rosy brown to brownish green with a long antennae. Apple aphids are green, black legged, with short antennae and cornicles. The apple grain aphid is light green with green legs and dark green bands on the abdomen. When high populations are present, especially of the rosy apple aphid, aphid feeding causes leaves to curl and stunting of the stems. They may also cause some distortion of fruit and a reduction in fruit size.