Low-Oxygen Atmospheres to Control Superficial Scald in Red Delicious Apples
The announcement by a federal regulatory agency that ethoxyquin and diphenylamine were under review prompted a search for alternate procedures to control superficial scald in Red Delicious apples. A preliminary study in 1980 indicated good control of scald with 0.5% and 1% oxygen atmospheres (Table 1). Further studies in 1981 and 1982 (Tables 2 and 3) with a spur and standard strain of Red Delicious gave results similar to those obtained in 1980. However, an earlier harvest (Sept. 22) in both years developed appreciable scald even in the low oxygen atmospheres. Scald was evaluated on fruit stored for 8 months in all years. Starkrimson, a spur type, tended to develop a higher incidence of scald than Harrold Red, a standard type. Control of scald was better in the 3 years with 0.5% oxygen than with 1% oxygen. Five grower lots in 1982 also responded more favorably to the 0.5% oxygen atmosphere (Table 4). A slight alcoholic flavor was found in some of the 1982 fruit immediately after storage but the taint had disappeared after 2 days at 68°F (20°C).Low oxygen atmospheres look promising for scald control in Red Delicious apples. Further research is needed to resolve the following problems: effect of harvest date, production of undesirable levels of ethanol in the fruit, and seasonal differences.
Plant Physiologist, Agriculture Canada, Research Station, Summerland, B.C. Canada, VOH lZO
Post Harvest Pomology Newsletter, 3(1): 14-16