New video explains how gibberellic acid supports citrus trees and reduces fruit drop

A treatment to support Florida’s citrus trees needs to be applied now to be most effective.

Plant growth regulators are one tool that Florida citrus growers can use to reduce fruit drop. But how and when they are applied on the tree are the keys, UF/IFAS researcher Tripti Vashisth said in a recent video produced by the UF/IFAS Citrus Research and Education Center.

Citrus greening disease (HLB) starves the tree of natural hormones  the trees need to produce healthy fruit. For example, trees naturally produce gibberellic acid (GA) to support vegetative and fruit growth, reduce fruit drop and suppress flowering in trees. HLB reduces the natural production of gibberellic acid, which is one of the reasons HLB-effected trees have smaller leaves than a healthy tree.

Vashisth, associate professor of horticultural sciences at the UF/IFAS Citrus Research and Education Center in Lake Alfred, Florida, has been studying the impact of applying GA on ‘Valencia’ trees over the last six years. Applying GA in five applications from September through January has improved yield, improved vegetative growth, reduced fruit drop and improved the overall health of the trees in her study.

Growers question if five applications are required and necessary.

“Five applications work, but we know growers may need to do fewer applications,” Vashisth said.  “We may not see the level of positive impact with fewer applications than we have seen with five applications.”

The number of GA applications and how growers can decide on the number of applications is further discussed in the video.

Vashisth also discusses how another plant growth regulator, 2,4 D, reduces fruit drop.  She has used GA and 2, 4 D together in three applications October, November and December and has seen a 25% reduction in fruit drop in early trials. Right now, 2,4 D is not labeled for three applications, so that change would need to happen with the companies producing the product.

Vashisth outlines specifics of how to effectively use GA applications on “Valencia” trees in a new video with CREC Director Michael Rogers. Growers may view the new video at the Citrus Research website.


The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents.  |  @UF_IFAS


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Posted: August 12, 2022

Category: Agriculture
Tags: Citrus, Citrus Research, Citrus Research And Education Center, Gibberellic Acid, Michael Rogers, Tripti Vashisth, Valencia, Video, Yield

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