Why Does My Cotoneaster Look Unhealthy?

Have the leaves, flowers, and branches blackened?

Are the leaves wrinkled and discolored?

Are the leaves pale and mottled?

Are the leaves yellow, stems and leaves are covered with small bumps?

Have the leaves been skeletonized and the branches webbed?

Are the leaves stippled with yellow and the foliage is webbed?

Do the leaves have brownish blisters on their undersides?

Fire blight is a fungal disease that causes new shoots to wilt suddenly, turn dark and die back. The disease eventually spreads, killing the whole plant. Prune out diseased tissue, cutting back at least 6" beyond the discolored area: destroy or dispose of prunings. Disinfect pruners after each cut in a 10 percent bleach solution. Spray copper or Bordeaux mix the following spring during flowering.

Aphids can be abundant on the undersides of leaves, secreting copious amounts of honeydew. These tiny insects can vary in color, green, pink, black, gray to completely white. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations. Ladybugs are their natural enemies.

Lace bugs are flat, dark-colored insects with lacelike wings that feed on the undersides of leaves. They cause leaves to turn yellow, then brown and eventually die. Treat plants with a commercial pyrethrin spray or dust if the damage is severe. Prevent problems by covering plants with row cover until they blossom.

Yellow leaves covered by small bumps are caused by scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

Cotoneaster webworms are yellowish-green to brown caterpillars that feed on leaves and spin silken webs around leaves and stems. Young plants may die and the older ones can be seriously weakened. Break up and remove the webs and spray plants with BTK.

Spider mites often cause problems for cotoneasters shrubs. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap or pyrethrin.

Pear leaf blister mites are microscopic mites that live and feed on the tissue inside leaves. They overwinter on buds and infest new leaves in spring. Spray plants in late winter with dormant oil or lime-sulfur.

If the trunk or branches have small holes in them and the limbs die or break off the culprits are borers. Numerous borers attack woody plants, mining the inner bark and wood of branches and trunk. Prune off borer-infested branches. If you see borer holes in your trees, probe into them with a flexible wire or inject a solution of parasitic nematodes. After treatment, seal holes with putty.