Tips to Keep Citrus Fruit on Trees

By Frank Giles

During the May All In For Citrus podcast, Michael Rogers, director of the Citrus Research and Education Center, discussed research on how applications of gibberellic acid (GA) can improve tree health and reduce fruit drop. The research is being conducted by Tripti Vashisth, an associate professor of horticultural sciences with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS). Vashisth presented her findings at the Florida Citrus Growers’ Institute.

Applications of GA have been shown to synchronize flowering in Valencia orange trees and reduce the plant hormones that induce fruit drop. GA also helps to reduce stress in HLB-infected trees and allows them to put reserves toward growing better-sized fruit.

Rogers stressed that multiple applications of GA in the fall and early winter months are critical to have any positive effects. Research shows five applications beginning in September are most beneficial.

“GA is a plant hormone and breaks down pretty quickly in trees, so the window of benefit is pretty small after one application,” Rogers said. “But when you are applying it month-after-month for four or five months, the cumulative benefits begin to show.”

Vashisth has begun research on applications of GA to Hamlin trees with encouraging early results similar to what she has observed in Valencia. This is important because fruit retention in Hamlin has been particularly hard hit by HLB. 

To hear more about GA’s beneficial impacts on fruit drop, check out the May episode of the All In For Citrus podcast. The podcast is a joint project of UF/IFAS and AgNet Media.

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