A new University of Florida-developed forecasting system could help citrus growers control postbloom fruit drop this winter, despite the predicted El Niño weather pattern that’s expected to bring more rain and moderate temperatures.
With an El Niño, forecasters expect above-average rain this winter and early spring. Increased rain improves the chances of fungal spores splashing from flower to flower in citrus groves, researchers with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) say. Those fungal spores cause a disease known as postbloom fruit drop (PFD).
PFD causes citrus fruit to fall off just after flowering, said Megan Dewdney, a UF/IFAS associate professor of plant pathology. After the fruit falls, it leaves behind a “button” on the tree — the part of the tree to which the fruit would normally be attached.
Dewdney, a faculty member at the UF/IFAS Citrus Research and Education Center in Lake Alfred, works with Natalia Peres, professor of plant pathology at the UF/IFAS Gulf Coast Research and Education Center in Balm, and Clyde Fraisse, a UF/IFAS professor of agricultural and biological engineering, on a web tool to help growers control PFD.
The system helps growers know the most appropriate times to spray fungicides on their citrus trees to minimize PFD. Following feedback from growers, the UF/IFAS researchers developed a new Citrus Advisory System with less information required to be entered into the model and adding visual forecasts.
“The system allows growers to receive forecast alerts to their phones of infections for areas of citrus trees they consider important,” Dewdney said. The mobile technology is based on weather data from the UF/IFAS-developed Florida Automated Weather Network.
PFD can appear explosively in a bad season, seemingly infecting every flower on a tree, Dewdney said. It can cause between 20 percent and 80 percent yield loss, depending on the severity of the conditions, she said.
As part of the research team’s continuing work on PFD, a graduate student, André Bueno Gama, is working on ways to further improve predictions. Gama is studying historical weather data and experiments to expand scientists’ understanding of the fungus’ biology so researchers can better see how the fungus grows.
Researchers also are testing chemical treatments for their efficacy against the fungus, and they’re evaluating fungicide programs for disease management.
The research, funded by the Citrus Research and Development Foundation, will give growers the information they need to rotate fungicides so they’re not using a treatment for which the fungicide has developed resistance.
“We need to know which fungicides work well together for adequate control,” Dewdney said. “The fungicides prevent the flower petals from becoming infected, but cannot prevent the loss of the small fruit of an already infected flower.”
To access the Citrus Advisory System, click here.
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