Key Features
- Discolored or black foliage
- Cankers on stems
- Shoot blight
Symptoms
Phythophthora is a group of soil-borne, fungus-like plant pathogens that cause disease on many host species. Only a few generalizations can be made about symptom development. Foliar infections result in greenish-brown sunken spots on leaves. These spots can progress back the leaf and form a reddish-brown sunken canker on stem tips. Leaves on affected branches wilt and turn brown. When viewed from a distance, symptoms can range from a few darkened stems to entire dead stems. Conditions that permit Phytophthora blight also favor Phytophthora root and crown rot.
Biology
Spores are splashed from soil to leaf surfaces. Poorly drained soil or wet sites favor disease survival and spread.
Management Recommendations
Avoid sprinkler and other forms of overhead irrigation. Drip-lines eliminate splashing which spreads the disease. Prune out cankered branches, cutting a few inches below the canker. Thin dense plantings to increase air circulation. Increase soil drainage and decrease soil wetness to reduce the spread of the pathogen in the soil. Irrigate when necessary to reduce drought stress. If symptoms appear, the application of fungicides labeled for Phytophthora control will prevent new infections.
Effective Pesticides
Active Ingredients include: Copper salts, Phosphorous acid salts
Resources
