Editor’s Note: Tripti Vashisth with share new information on the use of gibberellic acid treatments to improve health and yield of HLB-diseased trees in a virtual seminar on Sept. 21. Register here.
Researcher Tripti Vashisth told the recent Citrus Expo audience how fruit drop might be reduced through the use of nutrition and irrigation strategies, gibberellic acid and increased fruit size. Vashisth is a horticulturist with the University of Florida Institute of Food and Agricultural Sciences.
Vashisth suggested that growers “look into their irrigation and nutrition strategies” because fruit drop is associated with water deficits.
It is essential to ensure trees receive enough water during March to June, the fruit growing season. “It’s really important to keep your trees hydrated at that time,” Vashisth said.
The plant growth regulator gibberellic acid (GA) can also improve fruit growth while reducing fruit drop, Vashisth said. If applied in the fall, it can suppress next year’s flowering “which means less competition, so the fruit just grows better.”
She said a December GA application would be a good one to start with. “Be cautious using it later than January,” she warned, explaining that if GA is applied too late “it can cause over-suppression of flowering.”
Vashisth also urged fresh fruit growers to use caution with GA, because it will keep fruit green and can even reverse color break. “So, GA is a good option for sweet oranges that are going for juice, but you should be very cautious when using it for the fresh market,” she advised.
“Fruit drop is related to fruit size,” Vashisth said. “We are consistently finding that the small fruit are more likely to drop. So anything that we can do to improve size should have an impact.” She noted that improved water-use efficiency of trees will improve fruit size, as will GA.
Fruit dropping before it can be harvested has been a major problem for Florida citrus growers since HLB became prevalent in the state starting in 2005.