Black Spot Management Strategies Updated

Ernie NeffDiseases

CBS

The title of Megan Dewdney’s Citrus Expo presentation was, “Shorten the skirts? Whether skirting improves citrus black spot fungicidal management.” The answer was “no,” based on trials she conducted to make that determination. But while skirting doesn’t appear to improve citrus black spot (CBS) fungicide programs, she pointed out that “there are other good disease management reasons to skirt.” Dewdney is a University of Florida Institute of Food and Agricultural Sciences plant pathologist at the Citrus Research and Education Center in Lake Alfred.

Dewdney noted that CBS can cause up to 60% yield loss in severe situations with no management, while a 10 to 20% loss is more common in minimally managed blocks.

The disease is now found in five Southwest Florida counties: Charlotte, Collier, Glades, Hendry and Lee. But Dewdney said Hurricane Irma in 2017 likely spread the disease to the north. Although undetected so far, it’s possible it is now also in DeSoto, Hardee, Highlands, Polk and maybe other Central Florida counties. She added that growers in those areas should be scouting regularly for CBS symptoms. Any spread caused by Hurricane Irma would be in addition to normal disease spread, she noted.   

Dewdney presented the following management recommendations:

  • Apply fungicides, alternating copper with a strobilurin, a minimum of monthly. “Start May if dry in April, otherwise start applications in April” through the fall, a slide indicated. It added that coverage is key, so at least 125 gallons per acre should be applied slowly.
  • Determine if CBS is in your grove or area.
  • Manage leaf litter.
  • Remove as much dead wood as possible and destroy it on site.

Dewdney reminded growers that if they reduce or eliminate CBS management, the disease will return.

See Dewdney’s full presentation, which includes more information about results of her CBS field trial and additional details about CBS management.

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About the Author

Ernie Neff

Senior Correspondent at Large