- Weeping cankers
- Blighted shoots
- Death of individual branches
Phytophthora 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. Blight progresses slowly resulting in multiple years of dieback if untreated. When viewed from a distance, symptoms can range from a few darkened branch tips to entire dead branches. Conditions that permit Phytophthora blight also favor Phytophthora root and crown rot.
Spores are splashed from soil to leaf surfaces. Poorly drained soil or wet sites favor disease survival and spread. Phytophthora blight is not likely to kill the entire plant, however, is an indicator that the plants are at risk of Phytophthora root or crown rot infections.
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, application of fungicides labeled for Phytophthora control will prevent new infections.
Active Ingredients include: Copper salts, Phosphorous acid salts
