Category: Cucurbits
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Urgent: Powdery Mildew Found on Watermelon in Charleston, SC
From Clemson Plant Pathologist Tony Keinath. Powdery mildew was found on three cultivars of seedless watermelon at the Clemson Coastal REC on May 23, 2023. All watermelon crops in South Carolina should be 1) scouted for powdewry mildew and 2) if found, sprayed to prevent powdery mildew from reducing yields by up to 40%. When…
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2023 Fusarium Wilt on Seedless Watermelon Experiment – Week 5 Observations
From Clemson Plant Pathologist Tony Keinath This year’s Fusarium wilt experiment includes 3 seedless cultivars, 3 fungicide treatments applied via drip irrigation, and grafting. (This experiment is supported in part by a USDA SCRI grant.) Transplants were set April 5 in a field infested with Fusarium races 1 and 2. Right on schedule, symptoms of…
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Cucurbit Downy Mildew Found in SC
Prepared by Rob Last, Justin Ballew, and Tony Keinath. Cucurbit downy mildew was identified in South Carolina on 5/12/23. The identification came from butternut squash grown in a sentinel plot at the Coastal REC in Charleston. The same strain that affects butternut squash also affects watermelon and summer squash. Now that downy mildew has been…
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2023 Fusarium Wilt on Seedless Watermelon Experiment – Week 3 Observations
From Clemson Plant Pathologist Tony Keinath This year’s Fusarium wilt experiment includes three seedless cultivars, three fungicide treatments applied via drip irrigation, and grafting. This experiment is supported in part by a USDA SCRI grant. There also is a side experiment with SP-7 pollenizers grafted onto ‘Carolina Strongback’ rootstock and non-grafted SP-7 supported in part…
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Pythium Damping-Off of Seedless and Pollenizer Watermelons
From Clemson Plant Pathologist Tony Keinath. Stand loss in transplanted spring seedless watermelons is usually not a serious issue in South Carolina, due to relatively sandy soils in the major production areas. Two pathogens that can cause post-transplanting damping-off and plant death are the fungus Fusarium and the water mold Pythium. Fusarium can kill seedlings…
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How Seedless Watermelon Cultivars React to Fusarium Wilt: Average Results of 2021 and 2022 Trials
From Tony Keinath, Extension Vegetable Pathologist. As part of a large USDA Specialty Crop Research Initiative grant, I have been working with Dr. Jonathan Schultheis, Horticulturist at NCSU, to evaluate seedless watermelon cultivars grown in plots naturally infested with the Fusarium wilt fungus. The South Carolina trials were done in my Fusarium-infested field at the…
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2023 Gummy Stem Blight Control for Watermelon Growers: Early is on Time
From Tony Keinath, Extension Vegetable Pathologist. The recent freeze in the lower part of South Carolina more than ended the 2022 watermelon season. It’s not too early to plan for gummy stem blight control in 2023 to allow time to buy the right fungicides in case of shortages. As the saying goes, early is on…
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Charcoal Rot Showing Up in Cantaloupe
From Clemson Extension Agent Rob Last and Plant Pathologist Tony Keinath. Charcoal rot was identified in a cantaloupe crop in South Carolina this week. The fungus responsible for the disease is Macrophomina phaseolina, a soil-borne fungus that survives as microsclerotia. The fungus affects more than 800 host plants. These range from corn and soybean to…
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Resistance to Tebuconazole is Widespread in the Gummy Stem Blight Fungus in South Carolina
From Clemson Plant Pathologist Tony Keinath. Cucurbit growers should reduce the use of tebuconazole to manage gummy stem blight as the pathogenic fungus has become moderately resistant to this very commonly used fungicide. Seven watermelon fields were sampled in 2019 (six fields) and 2021 (one field) in Beaufort, Bamberg, Barnwell, and Hampton counties. Of 229…
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Downy Mildew Spreads to Charleston, SC
From Clemson Plant Pathologist Tony Keinath and Extension Agent Zack Snipes. Downy mildew was found on non-sprayed “sentinel” cucumbers at Coastal REC, Charleston, SC, on June 1. Two susceptible slicing cultivars (Silver Slicer and Poinsette) had 5% leaf area diseased, while the resistant cultivars Citadel pickling and DMR-NY401 slicing and the moderately resistant Bristol slicing…
The South Carolina Grower 