Phytophthora capsici:
In squash fields, Phytophthora capsici causes wilting, crown, root, and fruit rot, plant stunting and death. Since the disease results in a range of symptoms in squash it is often referred to as Phytophthora blight. Sporangia are formed on infected fruit and have a powdered sugar appearance. P. capsici is favored by rain and warm temperatures, and in the presence of water sporangia can differentiate into swimming zoospores. Water management has a high impact on disease development and surface irrigation water can be a source of zoospore spread. The pathogen has two mating types, A1 and A2, that form a survival thick-walled structure called the oospore when they come into contact. The oospore can overwinter in the soil and persist in infested soil for as long as 10 years. Watermelon and cucumber vines are typically less susceptible to P. capsici than squash. However, all fruits are highly susceptible, especially if they are in direct contact with soil.
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- Symptoms of Phytophthora blight on pumpkins include fruit rot. Image provided by Chris Smart, Cornell University.
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- Symptoms of Phytophthora blight on squash include wilt. Image provided by Chris Smart, Cornell University.
Factsheets
- Managing Phytophthora on Summer Squash and Zucchini, Michigan State University, 2016
Manejo de Phytophthora en Calabaza de Verano y Calabacín , Spanish translation, 2017 - Managing Phytophthora on Winter Squash and Pumpkin, Michigan State University, 2016
Manejo de Phytophthora en calabaza de invierno y en calabaza, Spanish translation, 2017 - Phytophthora Blight Factsheet, Cornell University, 2021
- Infección de Phytophthora, The Facts about Phytophthora Blight Spanish translation, Cornell University, 2017
- Are your cucurbits infected with Phytophthora capsici?, NC State, 2013
More information about Phytophthora blight
- Managing Mildews and Phytophthora Blight Successfully in 2019, Cornell Cooperative Extension
- Vegetable Diseases Caused by Phytophthora capsici in Florida
- Photo Gallery: Phytophthora Blight on Cucurbit Crops, Cornell University
- Phytophthora Blight and Its Management in Cucurbit Crops and Other Vegetables, Cornell University, 2022
- Phytophthora Blight of Cucurbits, Cornell University, July 2020
- Reduced tillage for Managing Phytophthora Blight and Other Soil-Borne Pathogens
