Diseases of onion and garlic (
Stemphylium leaf blight and stem rot
Stemphylium leaf blight is caused by the fungus Stemphylium vesicarium. Small, light yellow to brown and water-soaked lesions develop on leaves. These small lesions grow into elongated spots that frequently coalesce resulting in blighted leaves. Lesions usually turn light brown to tan at the center and later dark olive brown to black as the spores of this pathogen develop.
Stemphylium vesicarium normally invades dead and dying onion tissue, such as leaf tips, purple blotch and downy mildew lesions, injured tissue, and senescent tissue. Infection usually remains restricted to leaves and does not extend into the bulb scales. Lesions generally occur on the side of the leaf facing the prevailing wind. Long periods of warm wet conditions encourage disease development.
The cultural and fungicide practices suggested for control of purple
blotch are also effective for control of Stemphylium leaf blight and
stalk rot.
August 3, 2011