Beet Leaf Spot
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Beet Leaf Spot  Beet leaf spot is caused by a fungal disease which overwinters in residue from diseased plants or on seed. It is spread by rain splash, wind, insects, tools, and by hand. High humidity and warm temperatures encourage beet leaf spot. Susceptible Plants- Red beet, spinach beet, and sugar beet. Symptoms- Individual leaf spots initially occur on older leaves and then progress to younger leaves. Individual lesions are approximately one-eighth inch in diameter with ash-colored centers and purple to brown borders, and are circular to oval shaped . Cercospora leaf spot is distinguished from other leaf diseases (Alternaria, Phoma and bacterial leaf spots) by their smaller size and shape, and the presence of black These structures are easily seen as black dots with the aid of a hand lens (10X magnification). During periods of high humidity the black dots will be covered with colorless fuzzy masses of spores resembling cobwebs, which serve as the source for secondary infections within gardens and fields that season.
As disease progresses, heavily infected leaves initially turn yellow. Individual spots may coalesce and form larger areas of dead tissue, causing severely infected leaves to wither and die Severely diseased plants can be viewed at a distance when dead or dying leaves appear above the canopy, giving a burned or scorched appearance.
Disease often is unevenly distributed in fields usually being more severe in protected areas adjacent to windbreaks formed by trees or taller crops, or other areas that may result in higher levels of humidity. Prevention and Control- Clear up crop debris, use fresh seed. Initial inoculum potential depends on the survival of the fungus spores and Under favorable conditions in mid-summer, inoculum levels continue to increase and the life cycle of the disease may be completed within 10 days. Whenever beet leaf spots are observed, infection has taken place sometime in the previous 7-10 days, thus total infection present during favorable conditions is greater than what would be visible for up to 7 days. Fungicidal Control- Sulfur or copper based fungicides such as Liquid Copper Fungicide
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