Florida university designs tool to help control postbloom citrus drop

The University of Florida has developed a system designed to help growers know the best times to spray fungicides on their citrus trees in order to minimize a disease called postbloom fruit drop.

The disease causes fruit to fall from the tree just after flowering, according to a news release. Predicted above-average rain this winter and spring means a higher chance that the disease will be an issue in citrus groves. 

To use the system, growers can go to AgroClimate.org and select their area of the state, what stage their crop is in, when they last sprayed it, and they will receive an instant recommendation on whether to spray and what products the University of Florida’s Institute of Food and Agricultural Sciences suggests.

Megan Dewdney, an associate professor of plant pathology at UF-IFAS and a faculty member at the UF-IFAS Citrus Research and Education Center in Lake Alfred, Fla. has been working with two other researchers on the Citrus Advisory System.

The group developed it based on feedback from growers, and the new tool requires them to enter less information into the forecasting model to use it. Also, visual forecasts have been added.

The new tool is also designed to make monitoring easier.

“The system allows growers to receive forecast alerts to their phones of infections for areas of citrus trees they consider important,” Dewdney said in the release, noting that the postbloom fruit drop can cause 20% to 80% yield loss, depending on how bad conditions are.

Research ongoing

The group of researchers, including Natalia Peres, professor of plant pathology at the UF-IFAS Gulf Coast Research and Education Center in Balm, Fla., and Clyde Fraisse, a UF-IFAS professor of agricultural and biological engineering, continues to search for ways to combat PFD. 

Graduate student André Bueno Gama is looking at ways to improve predictions, examining historical weather data and conducting experiments so scientists will have a better feel for how the fungus that spreads PFD grows. The team is also evaluating different fungicide programs for disease management.

The research is funded by the Citrus Research and Development Foundation. 

“We need to know which fungicides work well together for adequate control,” Dewdney said in the release. 

“The fungicides prevent the flower petals from becoming infected but cannot prevent the loss of the small fruit of an already infected flower."