Gibberellic acid (GA), a plant growth regulator (PGR), has the potential to aid production. It can reduce citrus flowering, improve fruit size, reduce fruit drop and possibly improve tree health, says researcher Tripti Vashisth. Vashisth is a horticulturist with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) at the Citrus Research and Education Center (CREC) in Lake Alfred.
Vashisth says she and other researchers wanted to see what can be done to “reduce flowering, because citrus trees flower a lot” with less than 2 percent of flowering resulting in harvested fruit. Reducing flowering with GA “means fewer fruit,” leading to better fruit size and ultimately less fruit drop, she continues.
“Your timing is really critical” when utilizing GA, Vashisth says.
Vashisth offered her plant growth regulator comments last month at an OJ break hosted at the CREC by multi-county citrus Extension agent Chris Oswalt. Approximately 30 growers and others attended the OJ break that focused on several production issues. Only a few other UF/IFAS citrus events were held after that meeting and before the COVID-19 pandemic brought a temporary halt to UF/IFAS public gatherings.
A handout that accompanied Vashisth’s presentation offered several other take-home messages for HLB-affected citrus trees. One message was that good canopy equals less fruit drop. Other messages were that 1) “there are few PGRs available for citrus to manipulate flowering and fruit growth. 2) PGRs such as auxin, cytokinin and GA can be useful. 3) PGR efficacy is sensitive to growth state of fruit. 4) Timing is critical.”
Also in the handout was a section called “things to consider when applying PGRs.” They included concentration of active ingredient, spray volume, method of application, time of day, season, compatibility with other chemicals in the tank mix, type of adjuvant, weather conditions and tree health.
Hear more from Vashisth:
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