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A genus of fungi that is generally a root and crown rot pathogen. This is a common disease in periwinkles that are being grown using synthetic fertilizers and pesticides. Beneficial microbes in healthy organic soil will normally keep this disease organism under control. Lilacs, rhododendrons, azaleas, and some hollies are sometimes infected by Phytophthora fungi. Plants suffer shoot dieback and develop stem cankers. Prune to remove infected branches and to increase air movement. Add compost and rock powders to the soil. In healthy soil, plants rarely have this problem. On peppers, potatoes, and tomatoes, Phytophthora infection is known as late blight. The first symptom is water-soaked spots on the lower leaves that enlarge and are mirrored under the leaf with a white downy growth. Dark-colored blotches sometimes like sunken lesions penetrate the flesh of tubers. During a wet season, plants will rot and die. Phytophthora overwinter on underground parts and in plant debris. To control, dispose of all infected plants and tubers, presoak seed in a disinfecting solution such as hydrogen peroxide and plant resistant cultivars. Sprays of potassium sulfate can help control outbreaks during wet weather. This is the disease that has greatly reduced the use of periwinkles as a bedding plant. Healthy soil through the use of compost, natural organic fertilizers, and rock powders will help control the pathogen. Good drainage is critical. Whole ground cornmeal in the soil and cornmeal tea on the tea are both effective on this disease.


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