The June All In For Citrus podcast features Tripti Vashisth, associate center director and professor of horticultural sciences at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center. She discusses the benefits of combining plant growth regulators (PGRs) with trunk injection of oxytetracycline (OTC). For most Florida citrus growers, application of OTC has become a standard production practice to reduce HLB bacteria in trees.
Vashisth has led PGR research over several years. She said plant hormones like gibberellic acid (GA), cytokinins and auxins (2,4-D) can be used together throughout the year to enhance growth, reduce fruit drop and improve peel strength.
Her 3-year study has shown that combining PGRs with OTC injections provides better results than using either method alone, particularly in older trees.
GA is a versatile hormone that helps with shoot growth, peel thickness and preventing fruit drop, but keeps fruit peels green. Vashisth recommended that fresh fruit growers avoid spraying GA after August for early-season varieties and should limit applications to October for late-season varieties due to peel color staying green too long.
She also emphasized that multiple sprays of GA are essential, recommending at least three applications starting in June rather than a single spray in July. Single applications have shown no benefit in field trials. Vashisth advised using cytokinins in spring and early summer, while Citrus Fix (2,4-D) is most effective in fall to prevent fruit drop, particularly for Valencia oranges starting in October-November. She added that combining Citrus Fix with GA can help reduce fruit drop after hurricanes if applied within a 10-day window.
Don’t miss the June episode of the All In For Citrus podcast to learn more about PGRs in citrus. The podcast is a partnership between UF/IFAS and AgNet Media.
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