What Is Wrong With My Hawthorn?

Are the leaves curled and distorted?

Are there any brown blotches on the leaves?

Are there any chlorotic flecks on the upper leaf surfaces, the lower sides of the leaves are covered with small, brown, sticky flecks?

Have the leaves, flowers, and branches blackened?

Are there any small reddish-brown spots on the leaves which may run together?

Are there any orange or rust-colored spots on leaves leading to early defoliation?

Distorted and curled leaves are caused by aphids. These tiny insects cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

The leafminers don’t kill hawthorns, but an attack can leave the foliage looking charred and dead. They do leave the tree very vulnerable to attack by the Aphids. Prune off and destroy all infested leaves. Remove debris in fall because it might contain overwintering leafminers. Introducing parasitic wasps is a very effective method of controlling leafminers.

Lacebugs are only about one-eighth inch long and hard to see. The bugs feed by sucking sap from the underside of the leaves, and their excretions characteristically create many small, shiny spots. Treat plants with a commercial pyrethrin spray or dust if the damage is severe.

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.

Fungal disease leaf blight often attacks hawthorn leaves and twigs. Prune off all infected leaves and twigs to stop the disease from spreading. Thin plants to increase air circulation and allow sunlight to reach inner branches. Rake and destroy all fallen leaves and fruit.

Cedar-hawthorn rust is a fungal disease that spends part of its lifecycle on red cedar trees. The fruits and twigs of hawthorn are also attacked. Cut off and destroy all infected parts before early spring. Avoid planting Eastern red cedar (Juniperus virginiana) and its cultivars close to hawthorns.

San Jose Scale often attacks hawthorns. Clusters of these sucking insects cling to the bark and appear as small gray bumps that can be easily scraped off with a fingernail. Control them with late winter application of dormant oil spray.