What diseases can affect bulb crops? Listed below are several diseases that most frequently occur on bulb crops. Symptoms are described briefly. Colored pictures of disease symptoms can be seen in the publication "Identifying Diseases of Vegetables" available from the Penn State Publication Distribution Center, or from extension offices.
Leaf spots and blights: Spots appear on leaves and the leaves die. Control: Grow bulb crops in a sunny, well-drained area. Practice at least a 2-year rotation. If needed, especially for storage onions, use of fungicides as labelled will help.
Storage rots: Dry and wet rots develop in storage. Control: Grow bulb crops in a sunny, well-drained area. Practice at least a 2-year rotation. To allow adequate pre-storage drying of onions, promote early maturity by planting early, provide adequate space to grow the plants, and avoid excessive nitrogen fertilization. For onions, use of labelled fungicides for control of leaf spots and blights may help. At harvest time, undercut onions and later windrow until neck tissue is dry. If necessary, dry onions in artificial heat (90-120 degrees Fahrenheit for 2 or 3 days); then, if possible, use thick-necked bulbs immediately, and store adequately dried bulbs in an area that is dry and cool (32-34 degrees Fahrenheit).
Dr. Alan A. MacNab, Professor, Plant Pathology
Penn State College of Agricultural Sciences
211 Buckhout Lab, University Park, PA 16802
Loaded: June, 2003; AAM
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