Holly: Phytophthora leaf & 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 canker 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
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
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: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- 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
If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.