Researchers with the University of Florida’s Institute of Food and Agricultural Sciences (UF/IFAS) recently hosted a virtual seminar to help farmers protect their trees from the costly and incurable bacteria, citrus greening.
Citrus Greening, or Huanglongbing (HLB), is a bacteria that harms citrus trees by restricting the flow of nutrients throughout the plant, according to a paper from researchers at UF/IFAS. This damage contributes to fruit drop – the premature loss of too much of a harvest – that is indicative of unhealthy trees. Over time, HLB limits plant productivity and kills the tree.
The bacteria, which originally appeared in China, was first documented in Florida in 2005. Today, the Economic Research Service estimates that every grove in Florida has been affected by HLB. According to a paper from the Journal of Integrated Pest Management, HLB forced 4614 Florida growers to close in 2017 alone. Those in Florida’s poorest counties have been disproportionately affected by hardships in the industry, as they tend to be the biggest citrus producers, as described in the USDA’s Florida Citrus Statistics.
Dr. Tripti Vashisth, a UF Assistant Professor and Horticultural Sciences and Citrus Extension Specialist and Dr. Fernando Alferez, a Southwest Florida Research and Education Center (SWFREC) Citrus Horticulturist presented their research on fruit drop caused by HLB during the seminar. As two of just a handful of HLB researchers in the United States, their work gives farmers the tools to protect and treat their crops.
Vashisth tells Food Tank, “The trees usually drop some fruit but with the HLB we can see 40-50 percent of the fruit dropped.” She notes that the drop happens shortly before harvest, costing growers valuable revenue.
During the seminar, the researchers focus on new techniques that farmers can apply to reduce fruit drop in their affected trees. They also emphasize that farmers should work on preserving the overall health of the tree, rather than just focusing on fruit, in order to limit damage.
Alferez begins the seminar with a presentation of his current research, which looks into the biological processes that lead to fruit drop. According to Alferez, signaling systems and energy levels within the plants greatly influence fruit maturation in both healthy and affected trees.
According to his research, the application of zinc based fertilizers may help promote healthy fruit growth and mitigate drop. But for this intervention to have the greatest impact and encourage fruit growth, Alfarez says that the early application of fertilizer is key. His team will continue to test this research throughout the 2021 growing season.
Vashisth then presents her research, which suggests that application of the plant hormone, gibberellic acid, can prevent fruit drop. According to Plant Stimulating and Behavior, gibberellic acid stimulates plant growth and development. Her research focuses on preventing fruit drop early in the growing season. Vashisth’s research aims to provide farmers with easily applied treatment methods.
So far, the researchers report that they have received positive feedback from farmers, who say they better understand the importance of timeliness in treating affected trees.
Vashisth tells Food Tank, “In the last few years, we have learned that the fate of fruit that will drop is decided almost three or four months ahead. Anything you are doing to mitigate has to be done early in the season.”
Vashisth says that SWFREC continues to provide resources and learning tools for citrus farmers. She tells Food Tank, “We are looking into more enhanced irrigation strategies, that will be more of a demonstration for the growers.”
She hopes that together, these resources can help farmers intervene when there is still time to save their crops, so they can decrease fruit drop, improve harvests, and increase their annual revenue.
Photo courtesy of Philippe Gauthier