ReTain inhibits ethylene production in fruit. Hence it is used to delay ripening, reduce pre-harvest drop, and extend the harvest season. Since it’s about the time for the pre-harvest drop control sprays, I wanted to share with you a field trial we conducted last year in one of Galize Apples’s orchards, in Winchester. The purpose of this trial was to examine the effect of different rates and application timing of ReTain on fruit drop of Gala apples. The tables below show the effects of two application timings (1 and 3 weeks before harvest (WBH) and two rates (1/2 and full-rate) on fruit drop and fruit quality. To accurately evaluate fruit drop (%), we assigned 6 trees/treatment, and we flagged 100 fruit/tree. We counted these fruits every week starting 1 WBH and through four weeks after the normal harvest date. Last year, the expected harvest date of Gala was Aug 28, so we applied our sprays on Aug 9 and 23.
– As you can see from Table 1, Retain treatments decreased fruit drop percentage compared to the untreated controls, but the differences between untreated trees and treated trees were not STATISTICALLY significant at 1 WBH, at harvest and 1 WAH. However, for fruits that were left on the tree for 2, 3 and 4 weeks after the normal harvest date, ReTain treatment applied 3 WBH at full-rate (333 g/acre) has shown SIGNIFICANT reductions in the percentage of fruit drop compared to untreated trees (28% vs. 58%). These reductions in fruit drop can be translated to a 40-50% increase in the yield and two weeks extension to the harvest season. We also found that two applications of ReTain (1 and 3 WBH) at half-rate can give a similar effect to a single application (3 WBH) at a full-rate.
– As far as fruit quality is concerned, fruit samples collected from treated trees and untreated trees at harvest indicated that ReTain applied at the full rate 3 WBH has significantly delayed fruit ripening. Fruits treated with ReTain were firmer than untreated controls and had lower sugar, starch, and color values (Table 2). Similar results were obtained when fruits were collected 2 weeks after the anticipated harvest date (Table 3), but the differences between treated and untreated fruits were not statically significant.
