Category: Disease
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Grafting Reduces Southern Blight on Tomato by 83%
From Clemson Plant Pathologist Tony Keinath. Southern blight has become more common on tomatoes grown without fumigation throughout the southern United States. A joint project between the University of Georgia and Clemson University looked at grafting as a management option. In the 2021 trial in Charleston, SC, grafting reduced the percentage of diseased plants from…
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Timely Diagnosis
From Clemson Plant Pathologist Tony Keinath. Plants are a rich source of food for microorganisms—for aggressive plant pathogens, for weak pathogens, and for common saprophytes (the 90% of microorganisms that feed only on dead plant parts). Once a pathogen kills parts of leaves or side roots and we see dark brown spots, things change. The…
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Fog and Downy Mildew on Collards
From Clemson Plant Pathologist Tony Keinath. Foggy fall mornings are nature’s warning that conditions are favorable for brassica downy mildew to get started on collard and kale. Remember that because downy mildew affects the harvested, edible portion of the crop, control practices must be very effective to increase yields. Use the following practices to maximize…
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Not Planting to Manage Phytophthora Blight by Reducing Disease Risk
From Clemson Plant Pathologist Anthony Keinath and Clemson Agricultural Economist Felipe Silva. After an absence of several years, Phytophthora blight reappeared in South Carolina in July 2021 on three farms. As expected, the outbreaks were on two of the three most susceptible vegetable crops: 2 cases on pepper and 1 case on pumpkin. (Summer squash…
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Accidentally Infesting Fields by Moving Soil on Equipment or How to Exclude Soil Pathogens from Fields
From Clemson Plant Pathologist Tony Keinath. Most growers probably have heard that it’s possible to infest a “clean” (pathogen-free) field by moving soil on equipment. The question is how much infested soil is too much. The answer depends on the pathogen and where the soil is deposited. Some pathogens are present in soil at very…
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Preparing for Gummy Stem Blight in Fall Cucurbit Crops
From Clemson Plant Pathologist Tony Keinath. Gummy stem blight is more common and more severe on fall cucurbit crops than crops grown in the spring. The cooler weather and longer dew periods in the fall provide an ideal environment for the fungal pathogen to grow and spread. Gummy stem blight is most common on watermelon…
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What is NOT Proper Crop Rotation
From Clemson Plant Pathologist Tony Keinath. There seems to be some confusion about what is a proper crop rotation to manage diseases caused both by pathogens that survive a few years in soil and pathogens that survive in soil longer than anyone can measure. Here are some rotations I have heard about that are not…
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Downy Mildew on Watermelon Found in SC
From Clemson Plant Pathologist Tony Keinath. Downy mildew was found on watermelon this week in Allendale and Barnwell counties. Although downy mildew does not infect fruit, it reduces sugar content once 1 in 4 leaves (25%) are infected. All watermelons should be sprayed with a fungicide effective against downy mildew. See pages 214-215 in the…
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Cucurbit Downy Mildew Found In SC
Cucurbit downy mildew was found in SC this week in Bamberg, Barnwell, and Calhoun Counties. In each case it was found on cucumbers and for now severity seems low. This is about two weeks earlier than in the past couple years. If not already doing so, all cucumber and cantaloupe growers in SC should begin…
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Fusarium Wilt in Watermelon
From Clemson Plant Pathologist Tony Keinath. Fusarium wilt is showing up in watermelon fields and in research plots at Coastal REC in Charleston. The most telltale symptoms are wilting of a few leaves at the crown of the plant, wilting of one vine on a plant, or wilting without yellowing of a small plant. A…
The South Carolina Grower 