Preharvest Conditions that Influence 

 Scald Susceptibility on Delicious Apples 

 in Massachusetts 



Sarah A. Weis and William J. Bramlage 



Department of Plant & Soil Sciences, University of Massachusetts 



Superficial scald (scald) develops on apples dur- 

 ing or following long-term storage at about 32°F. 

 Many postharvest factors affect its development, but 

 the actual scald susceptibility of the fruit is deter- 

 mined by preharvest conditions and the maturity 

 of the fruit at harvest. Studies in England in the 

 1950s suggested that hot, dry weather during the 

 summer increased susceptibility while cool, dry 

 weather decreased it (Fidler, J. C. 1956. Food Sci. 

 Abstracts 28:545-554). Other studies in New Jer- 

 sey showed that cool temperatures (hours below 

 50°F) near harvest reduced susceptibility (Merritt, 

 R. H. et al. 1961. Proc. Amer. Soc. Hort. Sci. 78:24- 

 34). It also has long been recognized that low-light 

 intensity results in greater susceptibility, as seen 

 by the strong tendency for scald to form on the green 

 side of the fruit. Likewise, it is well known that as 

 fruit become more mature before harvest, scald sus- 

 ceptibility declines. 



In 1986, we began sampling apples and exam- 

 ining their scald susceptibility in relation to 

 preharvest conditions. In 1994, we published an 

 article [Fruit Notes 59(3):6-10] showing results of 

 experiments which demonstrated that low tempera- 

 ture, sunlight, and ripening all had independent 

 effects on scald susceptibility of Cortland and Deli- 

 cious apples. 



We have obtained large amounts of data on scald 

 development in relation to preharvest conditions 

 from colleagues around the world, to attempt to 

 determine statistically the importance of preharvest 

 temperature, light, and rainfall, along with matu- 

 rity at harvest (judged by starch-iodine tests), un- 

 der commercial conditions among years and among 

 many geographical areas. This assessment would 

 give a good indication of the importance of these 

 conditions to growers, might provide the basis for 

 estimating the effects of "unusual" conditions, and 

 hopefully might lead to a reliable scald prediction 

 system at the time of fruit harvest. 



Here we report on one small piece of these data: 

 the effects on scald susceptibility of Delicious in 

 Massachusetts. These data were collected over eight 

 years at the University of Massachusetts Horticul- 

 tural Research Center (HRC), Belchertown using 

 fruit from different blocks and of different strains. 

 Temperature and rainfall records were from the 

 HRC or from records of the Metropolitan District 

 Commission's weather station at the southern end 

 of the Quabbin Reservoir Light conditions were 

 estimated from the Quabbin records as full sun, 

 partly cloudy, or cloudy. 



Starch scores were determined on the day of 

 harvest. A total of 344 lots of fruit were included in 



Fruit Notes, Fal 



1995 



