Phytophthora is a genus of water molds in the oomycete group that causes destructive root, crown, stem, fruit, and foliar diseases in many ornamental and edible plants. Though often treated like fungi, they are fungus-like organisms more closely related to algae than true fungi.
In gardens and containers, Phytophthora commonly causes root and crown rot, where tissues become brown, soft, and unable to move water effectively. Symptoms often include wilting despite wet soil, leaf yellowing, dieback, cankers, fruit rot, or sudden collapse depending on the host plant and species involved.
These pathogens spread through contaminated soil, splashing water, irrigation runoff, infected nursery stock, and poorly drained conditions. Management depends on drainage improvement, sanitation, resistant varieties where available, and removing infected material.
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