Apple Scab

jul_3Apple-scab, Venturia inaequalis, is a fungal disease that affects leaves, fruit, and twigs of edible and ornamental crabapples, mountain ash, cotoneaster, pear, and hawthorn apples as well. Apple scab can diminish the aesthetic quality of an apple tree by early defoliation and unsightly blemishes on leaves and fruit. In some cases branch dieback can occur as the disease progresses. The disease rarely kills, but it can severely affect the health of the tree by reducing growth, vigor, and fruit production. Repeated infections can weaken the tree and make it a susceptible host to other diseases and or pests.

Noticeable Signs

Common signs of Apple scab tend to show:

  • brown to olive lesions on leaves in late spring eventually turning black.
  • heavily infected leaves turn yellow and then defoliate.
  • fruit can also display similar symptoms as to those on leaves.
  • Lesions on fruit will unevenly mature, crack, and turn brown and corky.

Treatment/Management

Reducing the chance of infection can be accomplished by raking and proper disposal of leaves in fall, watering at ground level, and proper pruning for better air circulation.

Two to three fungicidal spray applications in the spring, starting at bud break and continuing can also produce positive results. If wetter conditions exist a forth spray may be necessary.

Informational Packet (PDF)