Alternaria Leaf Blight Common This Year

From Clemson Extension Plant Pathologist Tony Keinath.

During the 2019 Cantaloupe Disease Survey, Alternaria leaf blight has been found in several fields. It was more common in fields that had not been sprayed recently than in fields sprayed on a regular schedule. It also was found in a field rotated only one year out of cantaloupe.

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Alternaria leaf blight lesions on cantaloupe leaf.

The FRAC Group 11 fungicides (Cabrio, Quadris, Flint) are the recommended fungicides. Although the gummy stem blight fungus is resistant to this group of fungicides, they still are very effective against Alternaria leaf blight on cantaloupe and anthracnose on watermelon.

Downy Mildew found in SC

From Clemson Plant Pathologist Dr. Tony Keinath:

The first SC report of cucurbit downy mildew this year came on June 6 from a crop consultant, who found it on cucumbers in Bamberg County. Growers should spray all cucumber and cantaloupe crops to prevent or manage downy mildew. The cheapest downy mildew fungicide is Ranman. It can be tank-mixed with chlorothalonil, mancozeb, or tebuconazole to add protection against fungal leaf spots, like gummy stem blight and anthracnose, that will start to spread with the rain. Another option is Orondis Opti, a pre-mix of Orondis and Bravo (chlorothalonil). Watermelon growers should be spraying with protectants, as downy mildew has been spotted on watermelon in south Georgia.

Downy mildew lesions on cucumber leaf. Note how they are delineated by the veins in the leaf. Photo from Dr. Tony Keinath.

For more info on downy mildew management in cucurbit crops, refer to this fact sheet.

Testing What Controls Downy Mildew in Cucumbers – and What Doesn’t

From Clemson Plant Pathologist, Dr. Tony Keinath.

Small growers can manage downy mildew on slicing cucumber and increase yields by growing a partially resistant cultivar, like Bristol, and spraying weekly with moderate-cost fungicides, like chlorothalonil rotated with Ranman. Trellising doesn’t help manage downy mildew. Read Dr. Keinath’s full article about testing cultural and chemical controls for downy mildew here.

The cucumbers ‘Speedway’ (front) and ‘Bristol’ (back) in non-trellised plots with foliage yellowing due to downy mildew on June 23, 2017. Photo by Anthony P. Keinath

American Foulbrood Found in Bee Hives in SC

The Department of Plant Industry (DPI) is informing the South Carolina Beekeepers Association (SCBA) Members that we have official confirmation from the Clemson DPI Bee Lab in Pendleton of American Foulbrood (AFB) in Pickens County. To be more specific, AFB was found near the town of Pickens and the positive AFB hives were removed from a small apiary there. We hope beekeepers will notify the Department if they are experiencing problems, especially in the affected area. This cooperation is very important since South Carolina does not require beekeeper registration.

In addition to the SCBA notification, the surrounding local associations in the affected area have been notified as well.

Below is a map of the affected area. Beekeepers should email or call if they are experiencing any issues.

AFB found in hives near the town of Pickens, SC.

This notification is provided to protect the beekeeping industry of South Carolina.

  • Clemson University
  • Department of Plant Industry Apiary Inspection
  • Brad Cavin
  • scavin@clemson.edu
  • 864-596-2933 ext.113