Abstract
In recent years, growers in the Indian River District have expressed concern about low soluble solids concentration (SSC), pound solids per box (PS/B) and poor grapefruit quality in general. Internal fruit quality data from the Florida Agricultural Statistics Service (FASS) for red and white grapefruit from 1968 to 2003 for the Indian River Citrus District were evaluated to see if changes had occurred that supported this concern. The historical data did not support the belief that a large decrease in SSC nor PS/B has occurred in recent years. Acidity levels in December did appear to be lower in the short term if February-March and October-November mean temperatures were higher, but large difference occurred in 2 to 3 year cycles that were not accounted for. Generally, SSC and PS/B were higher and acidity values were lower for red than white cultivars, and the difference was very consistent and pronounced the last 4 to 5 years. Recent trials with relatively new red cultivars and rootstocks were evaluated to see if their adoption in the River District might have resulted in significant changes in quality. Except for 'Star Ruby', the new darker red cultivars appeared to be more like 'Ruby Red' and not as low in SSC or PS/B as 'Marsh' (seedless white) in one trial. None of the scion cultivars were different in another trial. The use of the 'Smooth Flat Seville' rootstock clearly resulted in lower SSC and PS/B in grapefruit compared to trees on sour orange, but neither 'Carrizo' nor 'Swingle' were different from sour. For new plantings, growers should select moderately vigorous rootstocks, which have been shown to produce good internal grapefruit quality. Growers can partially overcome low solids early in the season by avoiding over irrigation, which dilutes soluble solids, and by selectively harvesting from the top and south side of the tree, where soluble solids concentration is higher, rather than selecting only for size.
