During the season, recommendations for citrus buds begin

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UF’s Tripti Vashisth resumed counseling on Nov. 21 and will continue to provide counseling every other week through spring

PUBLISHED ON November 21, 2022

LAKE ALFRED, Fla. — The University of Florida will resume regular flower bud advisories for growers as this winter begins a critical time for managing citrus groves.

UF Institute of Food and Agricultural Sciences Associate Professor Tripti Vashist restarted the guidelines on Nov. 21 and will continue to issue them every other week until early spring.

The guidelines provide important information on the intensity and timing of citrus blossoms. Growers use this information to determine when to spray to control Asian citrus, and when to stop spraying pesticides so that pollinators can be moved into or placed near citrus blocks.

Flower bud guidelines can be found on the UF/IFAS Center for Citrus Research and Education websites at Flower Bud Induction – University of Florida, Institute of Food and Agricultural Sciences (ufl.edu) or crec.ifas.ufl.edu/flower-bud-induction.

“This is going to be a La Niña winter, which means Florida will have above normal temperatures. However, the rainfall pattern is not very clear, but it is expected to be below average for at least the rest of the year. The next few weeks will be warmer and drier. The precipitation pattern in February-March is still unclear!” – said Vashist, who manages advisory information about flower buds. “Under these conditions, enough hours below 68 degrees Fahrenheit are likely to accumulate to induce economic levels of flower buds, but intervening warm periods during the winter can result in multiple flower cohorts and extended flowering.”

Flower bud recommendations are guided by the Citrus Bloom Monitor, which predicts the date(s) when citrus will bloom based on observed and forecasted weather conditions and other parameters (variety, expected yield, tree age and soil type). Growers can enter parameters specific to their grove to get a forecast. Knowing the date of flowering is important for managing flowering and other related events. The Citrus Bloom Monitor also provides specific recommendations for bloom control. The Citrus Blossom Monitor can be obtained from the consultation page or directly from: http://disc.ifas.ufl.edu/bloom

Blooms may be unpredictable this year, not only due to upcoming weather conditions, but also due to Hurricanes Jan and Nicole. The trees lost significant amounts of leaves and fruit and sustained high-speed winds and rain, which increased the level of stress on the trees. The presence of fruits on the tree prevents the formation of buds, therefore, with the loss of fruits, you can expect early flowering. However, the significant leaf loss that occurred in the last month also plays an important role in future flowering. Due to significant leaf loss, most trees turn red, so the use of carbohydrate resources, thus reducing carbohydrate levels, can reduce overall flowering. Under these circumstances and current weather conditions, Vashist does not expect significant early blooms, although she expects to see two or three cohorts of blooms. The situation will clear up in the next few weeks when temperatures are expected to drop.

Keep an eye on induction hours for your area and watch for forecasted warm spells from the weather service. Normal healthy trees can increase their induction by applying some drought stress. Unfortunately, with the vulnerable root system associated with HLB, growers should not risk heavier fruit drop prior to harvest of the current crop by using water deficits to prevent unwanted early vegetative growth and enhance flower induction. Based on weather forecasts, if you are concerned about early bloom in your area, applying gibberellic acid (GA) may prevent early bloom. There are many things to consider when using GA. Before using GA, visit the Flower Buds website for more information Flower Bud Induction – University of Florida, Institute of Food and Agricultural Sciences (ufl.edu) or crec.ifas.ufl.edu/flower-bud-induction.

– Ruth Borger, UF/IFAS