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Stemphylium leaf spot in spinach

First reported occurrence of this disease on Long Island was June 2019.  Symptoms were light gray to tan leaf spots ranging in size from about 1/16th of an inch to 1/2 an inch with larger spots being irregular in shape.  Spots initially can be gray-green, and with age they dry up and become papery in texture.

Favorable conditions are prolonged periods of leaf wetness when temperatures are moderate (64-75 F).  There were frequent rain events during spring on Long Island in 2019.

Symptoms of Stemphylium leaf spot were found throughout this small, transplanted planting, likely reflecting that disease development and pathogen spread started in the greenhouse when seedlings were in close proximity.  The pathogen can be seed transmitted.  Symptomless young leaves in the field pictures, which were taken a week after the picture of individual leaves, may reflect a preceding rain-free period.  The grower commented unaffected young leaves were not evident the previous week.  Older leaves are also considered more susceptible.  Diagnostic spores of Stemphylium were observed on a few spots after the leaves were incubated overnight under high humidity in a plastic box.

This occurrence in 2019 is the second confirmed report of Stemphylium leaf spot in the Northeast.  Reports of suspect occurrences are requested to obtain better understanding of its occurrence in the region and thus need for implementing management practices.

See also: Stemphylium Leaf Spot – New Disease of Spinach for Northeast Region

Stemphylium leaf spot in spinach

Stemphylium leaf spot in spinach

Stemphylium leaf spot in spinach

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