Phytophthora fruit rot on cucumber

Phytophthora capsici

In cucumber fields, Phytophthora capsici primarily causes fruit rot and on rare occasions, when the weather is favorable, it can infect cucumber seedlings. Sporangia are formed on infected fruit and have a powdered sugar appearance. Sporulation is favored by rain and warm temperatures. Water management has a high impact on disease development. In the presence of water sporangia can differentiate into swimming zoospores. 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. Phytophthora fruit rot affects all cucurbit crops.

Diagnostic Resources

• A Diagnostic Guide for Phytophthora capsici Infecting Vegetable Crops
  by: Camilo H. Parada-Rojas, Leah L. Granke, Rachel P. Naegele, Zachariah Hansen, Mary K. Hausbeck, Chandrasekar S. Kousik, Margaret T. McGrath, Christine D. Smart, and Lina M. Quesada-Ocampo
  Plant Health Progress (2021) Vol. 22, No. 3
• Cucumber Disease Key – Smart and McGrath Labs at Cornell Vegetables
• MyIPM for Vegetables – An App developed by the Southeastern Vegetable Extension Workers
• Plant Disease Clinics

Disease Control Information

• Are your cucurbits infected with Phytophthora capsici? Quesada Lab at NC State
• Managing Mildews and Phytophthora Blight Successfully in 2019 Cornell Cooperative Extension
• Phytophthora Blight – Smart Lab at Cornell Vegetables
  Infección de Phytophthora – Spanish translation, 2017
• Phytophthora Blight and Its Management in Cucurbit Crops and Other Vegetables – McGrath Lab at Cornell’s Long Island  Vegetables
• Phytophthora Blight in Cucurbit Crops – Long Island Horticultural Research & Extension Center at Cornell University
• Plant Pathology Disease Factsheets – Hausbeck Plant Pathology Research Lab at Michigan State University
  Managing Phytophthora on Cucumber
  Manejo de Phytophthora en Pepino – Spanish translation
• Vegetable Diseases Caused by Phytophthora capsici in Florida (2018, 2021) UF/IFAS Electronic Data Information System