32°F, a second set of samples was transferred to 70°F for 

 five days and then returned to 32°F. A third set of 

 samples was not treated in any way and served as 

 controls. 



Mcintosh and Cortland were kept at 32°F for 22 

 weeks, and Delicious for 25 weeks. At the end of 

 storage all samples were kept at 70°F for 7 days and then 

 evaluated for scald, measuring its intensity on the scale 

 of 1 = 1 to 10%, 2 = 1 1 to 33%. 3 = 34 to 67%, and 4 

 = more than 67% of the fruit surface affected. 



Results 



Results ofthe experiment are shown in Table 1. As 

 expected, Mcintosh ripened the most during the har- 

 vests and Dchcious ripx^ned the least, but in all cultivars, 

 changes took place. After storage, little scald devel- 

 oped on any of the control Mcintosh, but considerable 

 amounts developed on Cortland and Delicious. DPA 

 was very effective in controlling scald on Mcintosh and 

 Delicious, but was only partly effective on Cortland. 

 Warming had two opposite effects: it reduced scald on 

 Delicious, but it markedly increased scald on Mcintosh 

 and Cortland. 



Discussion 



As expected, as preharvest hours below 50°F in- 

 creased, scald susceptibility of Delicious decreased, 

 although the rate of decrease was somewhat more rapid 

 than we have usually seen. We have not attempted to 

 construct a predictive curve for Mcintosh because scald 

 has occurred too infrequently in our tests. However, our 

 predictive curve for Cortland is similar to that for 

 Delicious, and the data for controls in Table 1 do not fit 

 that curve. The first harvest should have produced 

 nearly 100% scald, but produced only 9% scald. We 

 have seen this happen before occasionally on early- 

 picked fruit, and do not know what causes it to occur. Of 

 more concern was the failure of scald to fall to very low 

 levels with more than 150 hours below 50°F (the final 

 two harvests of Cortland). Not only did the scald 

 susceptibility not decline as expected, but these fruit 

 also failed to respond fully to 2000 ppm DPA. (It is 

 possible that an unusual form of scald developed, one 

 that was not as controllable by DPA.) In our attempts 

 to predict scald susceptibility, we are more concerned 

 about underpredicting than about overpredicting scald, 

 because in the former case a grower might experience 



8 



Fruit Notes, Fall, 1994 



