Good Fruit Grower

August 2014

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Page 16 of 63 Good Fruit Grower AUGUST 2014 17 Split applications at 30 and 14 days did not add signifi- cantly to maturity delay. However, on McIntosh and other summer apples, early applications 30 to 21 days before harvest were more effective. From his research, Schwallier concluded that all rates and timings shut down ethylene production, but the best results came from ReTain plus NAA anytime from 30 to 14 days before anticipated harvest. In stressful years, ear- lier is better, and the rate of ReTain can be increased for better effect. The size of the crop also plays a role, Schwallier found. The heavier the crop, the greater the effect of ReTain on slowing apple maturity. Stopping drop and delaying maturity are not the same thing. Schwallier said ReTain improves fruit quality, firmness, and shelf life, reduces greasiness and incidence of watercore, and reduces cracking as well as stopping drop. NAA stops drop but advances maturity on some varieties, such as McIntosh. "One single application of ReTain made at the full rate will satisfactorily retard drop for about 35 days in normal years," Greene said. "After that, drop starts to increase, and a supplemental application will be neces- sary to extend the drop control period." Greene also found that earlier application is better if the goal is to delay ripening. The earliest time of application suggested on the label is four weeks before anticipated harvest. This timing results in the maximum delay in ripening. Split applica- tions of a half rate of ReTain applied at four and two weeks before anticipated harvest are not as effective in delaying ripening. He recommends the full-rate strategy for pick- your-own and other blocks intended for late harvest. In an effort to reduce cost, Greene experimented with adding NAA and reducing the rate of ReTain. But it resulted in a "fickle drop control strategy." In the last five years, the addition of NAA to ReTain enhanced drop control in two years but not in the other three, he said. "Research over these past several years clearly shows on McIntosh types that ripening will be advanced if the ratio of NAA to ReTain is too high. Advanced ripening is unlikely if a half rate or greater of ReTain is used with 10 ppm NAA. If more NAA or less ReTain is used, rip- ening is most likely to be advanced. In some situations where too much NAA is applied with ReTain, drop may be increased. Application of 20 ppm NAA or more than two applications of 10 ppm NAA may advance ripening." Harvista During the last few years, MCP (1-methylcyclopro- pene) has been adapted from its role as an in-storage treatment (SmartFresh) into an orchard spray (Harvista). "Harvista is not available in the East," Greene said, "It is a good stop-drop material, but it works differently than ReTain." While ReTain stops the production of ethylene inside the apple and prevents it from reaching the climateric threshold level, Harvista attaches to ethylene binding sites in fruit and prevents ethylene from ripening the apple. "Once attached, Harvista never lets go," Greene said. "However, the apple does develop new binding sites and then drop occurs." In New York, Cornell University horticulturists Dr. Terence Robinson and Steve Hoying think Harvista would be a great addition to the stop-drop arsenal for McIntosh. It is rapid acting and only need be applied approximately seven days before harvest and gives com- parable results to the best ReTain plus NAA treatments they have tested, they report. In addition, this material preserves firmness through storage. • F ruit drop just before harvest is a serious prob- lem for some apple varieties grown in New York, according to Dr. Terence Robinson and Steve Hoying of Cornell University, New York. Many commercial apple growers with sen- sitive varieties lose 5 to 25 percent of their apple crop due to preharvest fruit drop, which occurs just before fruit develop optimum red color, maturity, and size, the horticulturists write in a publication about the use of stop drops. They list these four rea- sons why applying a stop- drop material is important: —First, to keep apples on the tree until they reach physiological maturity. McIntosh, Macoun, and Honeycrisp drop before they are physiologically mature. Apples picked before maturity are small, undercolored, starchy, have a poor taste without vari- etal flavor or sweetness, and do not store well. —Second, to allow apples extra time on the tree to increase fruit size and yield and to obtain marketable color. Some varieties such as McIntosh will drop as they wait for color. Since environmental conditions with warm days combined with cooler nights trigger color development, applying stop drops will delay harvest, sometimes pushing apples into windows of improved weather for coloring. Fruit size and total yield also increase since apple size continues to increase. —Third, to hold apples on the tree for an extended period of time so that they will be available for extended harvest, as in you-pick situations. "You-pick operations rely on the public to harvest the fruit," Robinson and Hoying wrote in a paper on the subject. "Often the success of these operations depends on having a wide variety of fruit available for picking at any one time. Most consumers do not realize that the optimum picking window is relatively short, and the less experienced expect their favorite vari- ety to be available throughout the fall. Growers try to accommodate these con- sumers by having the wid- est variety of fruit available through the harvest win- dow by using a number of tactics. Delaying maturity and preventing fruit drop are two of these strategies." —Fourth, to manage the harvest season when there are too many apples to harvest during the time window available with the labor available. A grower can, by applying ReTain at different times to different blocks, extend the harvest season for a single variety for either labor supply or marketing reasons. Perhaps a fifth reason is the low value of dropped apples. Not only have sweet cider prices been pushed down by imported apple juice concentrate, but salvag- ing of dropped apples for juice is being discouraged in several states. While pasteurization eliminates the risk, marketers are increasingly concerned about the apple image and consider any risk too much risk. Dropped apples left in orchards, on the other hand, produce objectionable odors, attract wasps, and in other ways make harvesting difficult for hired workers and for you-pick customers. • —R. Lehnert Our fi elds are planted with the most popular semi-dwarf and dwarf varieties: LIKE OUR ROOTSTOCK, our service will grow on you. ALL FRUIT TREE ROOTSTOCK IS OREGON CERTIFIED VIRUS FREE. M.7/M.26/M.9 EML A BUD 9 NIC ® 29 PAJAM 2 ® M.9 NAKB T-337 GENEVA ® 202/30/16/11 c a n b y , o r e g o n 5 0 3 - 2 6 3 - 6 4 0 5 T o l l F r e e 1 - 8 0 0 - 8 5 2 - 2 0 1 8 We also grow a great selection of rootstock varieties for apple, cherry, peach, pear and plum including: APPLE MALUS ANTONOVKA MALUS DOLGO MALUS DOMESTICA CHERRY PRUNUS AVIUM PRUNUS MAHALEB PRUNUS EML A COLT PEACH PRUNUS BESSEYI PRUNUS PERSICA 'LOVELL' PEAR OH X F 87/97/333/513 PYRUS CALLERYANA PYRUS COMMUNIS PYRUS USSURIENSIS PLUM PRUNUS CERASIFERA PRUNUS MARIANA PRUNUS MYROBAL AN PROVENCE QUINCE See our newly updated website, with all of our offerings & availabilities at w w w. w i l l a m e t t e n u r s e r i e s . c o m Come see us at the Far west Show Booth #18015 Why STOP DROP? There are at least four good reasons. Many apple growers with sensitive varieties lose 5 to 25 percent of their apple crop due to preharvest fruit drop.

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