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Phytophthora crown and root rot (Phytophthora spp.) is caused by a soilborne water mold pathogen that favors wet conditions. Phytophthora infects roots and crowns (bases) of vines. Often, symptoms appear after a rainy season; disease is more prevalent in heavy or poorly drained soils. Newly planted vines are especially susceptible. Root loss and/or crown decay result in disruption of water uptake, and symptoms resemble drought stress. Leaves become chlorotic and plants become stunted; plants may die back slowly or may die abruptly. Wet conditions initiate spore production (sporangia containing zoospores); spores are transmitted via running water or infested soil. The pathogen overwinters as oospores in infected roots and crowns.

Phytophthora crown and root rot symptoms.

(Photo: Dean Volenberg, University of Missouri)

Management:

• Begin with clean stock.
• Improve internal drainage.
• Plant onto raised beds.
• Avoid movement of infested drain water or infested soil.
• Destroy infected plants before disease spreads to nearby vines.
• Specialty fungicide drenches help suppress disease as long as applications are made; these products do not cure disease.

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