How to Manage Pests

UC Pest Management Guidelines


Stemphylium Leaf Spot

Pathogen: Stemphylium botryosum

(Reviewed 3/17, updated 3/17)

In this Guideline:

Symptoms and signs

A tan center and a dark border around an irregularly shaped lesion distinguish Stemphylium leaf spot from other leafspot diseases. Once the border is formed, the spot ceases to get larger in size. New spores will form in the center of the leaf spot.

Comments on the Disease

Stemphylium leaf spot is a cool-season foliar disease. Cool temperatures (60–70°F) and moist weather favor infection and spread. The disease is usually found in first and second cuttings. Because defoliation occurs only under heavy disease pressure, Stemphylium leaf spot is not considered as serious as some other leaf spot diseases.


No known control measures are used. Early harvest is an option with severe infestations. Some varieties may have more levels of resistance than others, but companies do not commonly report resistance to this disease.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Alfalfa
UC ANR Publication 3430


R. M. Davis, Plant Pathology, UC Davis (Emeritus)
C. A. Frate, UC Cooperative Extension, Tulare County (Emeritus)
D. H. Putnam, Plant Sciences, UC Davis

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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