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Purple Blotch
(fungus - Alternaria porri): The fungus usually infects dead or dying leaf tissue. The first symptoms are small, white, sunken lesions. These lesions develop purple centers and enlarge [Picture]. The infection can encompass much of the leaf, leading to the death of tissue above the lesion [Picture]. The disease can be controlled with fungicides. In the Rio Grande Valley of Texas, the need to apply fungicides can be determined by monitoring leaf wetness during the growing season. Leaf wetness occurs as the result of dew, fog or rain. The action threshold is 12 hours of continuous leaf wetness.

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