Issue link: https://read.dmtmag.com/i/616629
www.goodfruit.com GOOD FRUIT GROWER JANUARY 1, 2016 25 not be mixed with calcium, according to the product label. Greene said he believes this is because calcium products inacti- vate Apogee. For maximum growth control, Greene recommends applying Apogee very early in the season — as soon as there is enough leaf area to absorb the compound. He thinks petal fall applications are too late because by then the shoots are growing rapidly. Apogee does not stop growth immediately when sprayed on the tree, so shoots can grow significantly during the 10 to 14 days it takes for the compound to work. "If you don't get it on early, you're going to lose a real opportunity," he warned. In Massachusetts, Greene applied Apogee in a mature block of Cortland apples to illustrate its effects to growers. The trees grew on Malling 26 rootstocks and were overly vigorous. This had been aggravated by heavy pruning each year. Flower bud formation and fruit set were poor, and the apples were large, green, soft, affected by bitter pit, and had poor storage potential. The block had never been productive. Greene tested two treatment timings with Apogee at a rate of 9 ounces per 100 gallons of water: one at the pink stage of bloom and the other at petal fall. The pink-stage treatment resulted in more open trees, better light penetration and improved fruit set. With the petal fall timing, much of the growth retardant effect was lost, he reported, although it did increase fruit set and opened up the trees somewhat compared to untreated trees. Rates In a trial on McIntosh apples, Greene assessed the effect of various rates of Apogee on fruit set and return bloom. Rates tested were 125, 250 and 375 parts per million. Fruit was thinned based on the needs of the control treatment. Trees treated with the lowest rate set 5.3 fruit per square centimeter of limb cross-sectional area versus 9.8 for the highest rate. However, the lowest rate had the highest return bloom (8.4 fruit per centimeter of limb cross-sectional area) versus 3.3 for the highest rate. "As we increase the amount of Apogee we get increases in fruit set, but the reduction in return bloom is a problem," he said, noting that growers should adopt a more aggressive thinning program in trees treated with Apogee. Growers in the eastern U.S. tend to use lower rates of Apogee at first but apply it more frequently. This is because they sometimes have difficulty thinning the crop adequately and the theory is that using lower rates initially will reduce the increase in fruit set, though this has not been proven, Greene said. Last year, he did an experiment with Fuji to study the effect of different rates of Apogee on fruit set. He applied 3, 6, 9 or 12 ounces per 100 gallons in late May when shoot growth was 1 to 2 inches long. All the treatments increased the crop load in comparison with the control. The 3-ounce rate set as much fruit as the higher rates, suggesting that Apogee did not increase initial fruit set, but the reduction in vegetative growth retarded June drop. Greene said it is not clear why there was no statistically significant rate response in the Fuji trial, as there was in the McIntosh study, and he intends to conduct another experiment to clarify this. He also studied how long the effect of Apogee endured in the trees before the compound was metabolized and the shoots began to regrow. Only trees treated with the 3-ounce rate regrew. The higher rates controlled growth for the whole season, but much of this growth was attributed to added weight because the terminals were pulled down horizon- tally by the weight of the fruit. • and retain firmness. It works by preventing SAM (S-adenosylmethionine), which is a precursor of ethylene, from synthesizing into ACC (1-aminocyclo- propane-1-carboxylic acid) and then into ethylene. Faubion said AVG applied before harvest helps get the fruit into storage in good condition, but is unable to prevent the apples from reacting to ethylene in the storage room. It does a better job in controlled-atmosphere (CA) stor- age than in regular storage because low oxygen, high carbon-dioxide, and low temperature all help to inhibit ethylene production. 1-MCP (1-methylcyclopropene), sold by AgroFresh under the trade name Harvista, works by blocking the ethylene receptors in the fruit, making it unable to detect ethylene. It can be applied before harvest by air (helicopter) or ground and takes effect more quickly than AVG, Faubion said. It controls fruit drop and also can maintain fruit firmness in storage because fruit may still be unable to detect ethylene in the environment. Harvista combined with a postharvest treatment of MCP (SmartFresh) is the best of all in terms of maintaining fruit quality, he said. 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