Abstract
In Florida, mechanical harvesting of citrus stops around 1 May every year as growers observe inch-diameter green fruitlets being removed by the shaking operations. Previous research by Hedden, Coppick, Whitney, and others found that 'Valencia' [Citrus sinensis (L.) Osb.] yields decreased by at least 20% when trees were shaken in early June of the prior year. The question addressed by this study was whether decreasing the duration of a trunk shaker or varying the frequency of a canopy shaker would lessen the yield impacts when 'Valencia' trees were shaken after 15 May. In 2003, an experiment was designed to measure the yield impact on the 2004 'Valencia' orange crop when trees were mechanically shaken at 2-week intervals from the first week in May through mid-June 2003. On four harvest dates, seven mechanical harvesting intensity treatments were replicated four times in a commercial, 15-year-old, 'Valencia' orchard near Immokalee, Florida. Treatments included three durations of a trunk shaker (4, 7, and 10 seconds) and three frequencies of a canopy shaker (215, 230, and 245 cycles per minute) along with handpicked control plots. The harvest treatments were repeated on the same trees on approximately the same harvest dates, oneyear later in 2004. Significant differences in yields were attributable to delayed harvest and to mechanical harvesting treatments. Yield reductions, as compared to the hand-picked controls, ranged from 20 to 50% depending on duration and frequency of shake.
