Black Spot and Production Guide Updates

Ernie NeffDiseases

black spot
Orange infected with citrus black spot
Photo by Megan Dewdney

Megan Dewdney recently provided information about positive results from fungicide trials for citrus black spot, as well changes to the new Citrus Production Guide. Dewdney is a plant pathologist with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), working at the Citrus Research and Education Center.

Dewdney conducted the fungicide trials for black spot in a 20-year-old Valencia orange grove with Ozgur Batuman, a fellow UF/IFAS plant pathologist at the Southwest Florida Research and Education Center. The scientists performed treatments with 10 different products.

All products but one worked better at controlling black spot than an untreated control. Dewdney said that one product may not have worked as well because the block it was in had more disease than other blocks that were treated.

“Just about everything else had far better disease management than the untreated control,” she said. “That means that probably growers are able to select just about anything that we have registered and they all will manage black spot pretty well. We saw the same results looking at the number of dropped fruit. The majority of the treatments had a reduction in the number of dropped fruit as well. So that’s an important part of black spot management — making sure that the fruit stays on the tree. The more disease you have, the fewer fruit will remain on the tree.”   

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Learn more about the black spot field trials, including the products tested, in Dewdney’s interview in the September episode of the All In For Citrus podcast, a joint project of UF/IFAS and AgNet Media. Listen to the full podcast.

Regarding the new UF/IFAS Citrus Production Guide, Dewdney discussed changes made to sections on canker and citrus tristeza virus. She said products recommended in the guide must go through at least two years of field research by credible scientists.

Dewdney and fellow UF/IFAS scientists Lauren Diepenbrock and Tripti Vashisth edit the production guide.  

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Ernie Neff

Ernie Neff

Senior Correspondent at Large

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