Holly: Phytophthora leaf & twig blight

categories: Holly Holly Diseases Ornamentals Shrubs

revision date: 2022-12-02 12:00

Holly Phytophthora leaf and twig blight.
Holly Phytophthora leaf and twig blight
Photo by: J.W. Pscheidt

Biology

Leaf and twig blight of holly is caused by a different Phytophthora species than is associated with root rots. Symptoms first appear in the fall and winter during wet, cool weather. Leaves develop purple to black spots and may drop from the plant. Twigs develop cankers and die back. The disease begins on the lower portions of the plant and progresses upward through the winter. Disease development usually stops in the warm, dry weather of summer. Phytophthora leaf and twig blight is mainly a concern in nurseries and holly orchards.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • Space plantings and prune to provide good air circulation.
  • Avoid overhead watering.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • Make the first application before fall rains begin.
  • Additional applications after harvest or severe winter storms may be useful.
  • Homeowners should not make foliar applications to trees over 10 ft tall.
  • Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.