Skip to main content
ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #315454

Title: Epidemiology and control of spinach downy mildew in coastal California

item CHOUDHURY, ROBIN - University Of California
item KOIKE, STEVEN - University Of California - Cooperative Extension Service
item SUBBARAO, KRISHNA - University Of California
item Klosterman, Steven
item MCROBERTS, NEIL - University Of California

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/21/2015
Publication Date: 8/1/2015
Citation: Choudhury, R., Koike, S.T., Subbarao, K.V., Klosterman, S.J., McRoberts, N. 2015. Epidemiology and control of spinach downy mildew in coastal California. Phytopathology. Available:

Interpretive Summary:

Technical Abstract: The most serious threat to global fresh market spinach production is spinach downy mildew, caused by the obligate biotrophic pathogen, Peronospora effusa. Downy mildew causes yellow chlorotic lesions on spinach leaf tissue, often accompanied by abundant sporulation on the undersides of leaves. Very little is known about the environmental parameters that affect spinach downy mildew development and how the pathogen disperses within a growing region. Spore traps linked to a species-specific qPCR assay were set up at four sites throughout the Salinas Valley in 2013 and 2014. Disease ratings were conducted in fields nearby the spore traps to link disease incidence with inoculum levels and weather conditions. Results from the spore trap study suggest there is a periodicity to the spore density in the air. Disease ratings in the vicinity of traps show a high correlation between disease incidence and airborne spore density. Logistic regression analysis suggested that cool temperatures and high wind result in increased airborne spore density. Commercially available biofungicides were compared for efficacy in field studies. Several products showed activity against downy mildew and may be useful for disease control. Results from a single trial suggested cultivar mixtures did not give disease control sufficient for commercial use.