INTERACTIVE EFFECTS OF COOL TEMPERATURES AND RIPENING ON SCALD RESISTANCE IN APPLES

Apples generally become less susceptible to scald as the season progresses and the fruit ripen. However, ripening effects may be confounded with effects of low temperature. Over 3 seasons we tested interactive effects of hrs < 10°C and ripening on scald susceptibility on Cortland apples. Ripening was induced by 500 ppm ethephon. In 1989, ethephon advanced ripening, increased endogenous antioxidant concns, and reduced scald incidence by 30% when 62 hrs <10°C had occurred before harvest. In 1990 no hrs <10°C had accumulated at harvest. Ethephon increased endogenous antioxidants and advanced ripening, but had little effect on scald development (>90% incidence). Low temps during ripening may be needed for ripening to induce scald resistance. In 1991, ethephon was applied once to apples at 6 different stages of development. Fruit were harvested a week later, after 14-156 hrs <10°C. Ethephon advanced ripening at the first 4 applications, but at the first 3 insufficient cool temperatures had occurred to expect scald reduction unless ripening had an independent effect. Results will be presented and discussed.