Excerpt from the article “Resurgence of Perennial Phytophthora Canker Disease of Almonds” by Mohammad Yaghmour, UC Cooperative Extension, Kern County, Greg Browne, USDA-ARS, Department of Plant Pathology, UC Davis and Brent Holtz, UC Cooperative Extension, San Joaquin County on the San Joaquin Valley Trees and Vines website.
Many species of Phytophthora continue to cause serious losses in California almond orchards. Collectively, these pathogens affect almond trees of all ages, causing decline and death in young orchards in their first few years of development as well as in bearing and fully mature orchards in their prime. As almond acreage continues to expand onto heavier ground and finer textured soils in the Sacramento Valley that can have difficulty with drainage, it is critical to understand the many forms Phytophthora symptoms can take, how infections occur, and how to avoid them.
See this article on San Joaquin Valley Trees and Vines to learn more about infection and management of Phytophthora.