Phytophthora blight

Phytophthora diseases are caused by fungus-like organisms of the genus Phytophthora. In tomatoes, Phytophthora infestans causes late blight, the development of which is favored by cool, damp weather. Other species of this genus can cause root rot and stem-base rot. These diseases develop primarily in the presence of free water in the soil, and some are also favored by higher temperatures. The conditions for development and the symptoms therefore depend on the pathogen species and the site of infection. First, determine which type of Phytophthora disease the symptoms indicate; until a diagnosis is made, it is advisable to limit watering, improve drainage, and isolate heavily infected plant material.