Increasing Yields of the 'Minneola,' 'Robinson' and 'Osceola' Varieties with Gibberellic Acid Sprays and Girdling

Abstract

Spray applications of gibberellic acid (GA) and girdling materially incerased the yields of seedless fruit of Minneola', Robinson' and 'OsFlorida Agricultural Experiment Station Journal Series No. 3743. ceola' tangelos; however, GA delayed develop ment of orange peel color 1 to 2 weeks. Vigorous trees with a strong, heavy bloom responded best. GA, which occurs naturally in the fruit of citrus, is cleared for use on several varieties of citrus, including the 'Orlando* tangelo. Only minute amounts of GA applied to the bloom are required to increase yields. No increase of GA concentration is detectable at harvest. Even so, this material is not cleared for use on 'Minneola', 'Robinson' or 'Osceola Yields from these varieties were increased by girdling; however, commercial girdling is often 30 FLORIDA STATE HORTICULTURAL SOCIETY, 1970 done poorly, resulting in less than the expected yield increase. Girdling old, virus-infected 'Minneola' has caused gumming and scaly bark at the cut and a few trees have declined. 'Robinson' were girdled only on individual limbs because this variety has had a dieback problem from an undetermined cause, but no girdling damage was found. Only a few 'Osceola' were girdled because of the limited number available. Thus, girdling of 'Minneola' should be performed only on vigorous trees with strong blooms and used only in trial amounts on 'Robinson* and 'Osceola'.