Citrus Advisory System Provides PFD Alerts

Ernie NeffDiseases

Damage from postbloom fruit drop includes buttons where fruitlets fell off.
(Photo by Megan Dewdney, UF/IFAS)

Beep. Beep. Beep. That’s the sound of an alert telling a citrus grower it’s time to spray fungicide to help prevent fruit from falling off the tree due to postbloom fruit drop (PFD).

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers have developed a Citrus Advisory System (CAS) that sends web-based alerts to growers via mobile devices.

PFD can cause major losses. It can lead to crop loss of up to 80 percent, although losses are seldom that high, according to researchers.


“We believe that CAS represents an important contribution to help the citrus industry in Florida increase resource-use efficiency, reduce costs and increase profitability,” said Clyde Fraisse of UF/IFAS. Fraisse is a professor of agricultural and biological engineering in Gainesville who led new research to develop and test the system.

Fraisse, his lab members and faculty colleagues tested CAS over three years at groves in Polk County. Among those who helped Fraisse with the research were UF/IFAS plant pathologists Megan Dewdney and Natalia Peres.

CAS, available here, uses real-time weather data from Florida Automated Weather Network stations, which are scattered throughout the state. The data determine whether risk for PFD is low (green), moderate (yellow) or high (red). Specific fungicide spray recommendations are given according to the disease-risk conditions.

Prior to CAS, there were two forecasting models for PFD, Dewdney said. The most recent was the PFD-Fungicide Application Decision (PFD-FAD), which was developed as part of Peres’ Ph.D. dissertation about 20 years ago. Growers found PFD-FAD too complicated to use regularly since the weather information was not automated, and it required grower input to determine if the fungus was present. 

“In the new CAS, we consider the fungus to be present at all times, and the weather data input is automated, so the system is simpler to use,” Dewdney said. “We also have newer models for how leaf wetness and temperature affect spore germination. They’re incorporated into the system to help predict when infection is likely to happen or has occurred. Combined with a more modern, simple interface, this will hopefully allow growers to use CAS regularly. During our last outbreaks, many growers were applying weekly fungicide applications, whether they were needed or not.”

Source: University of Florida Institute of Food and Agricultural Sciences

Share this Post