Predicting Delicious Apple Storage Scald

September 20, 2000

Scald on New England grown Delicious apples. Upper left, no scald to lower right, slight, moderate, and severd scald.

Scald can be an important post-harvest storage disorder of Delicious apples in New England (see picture). Although the exact causes of scald are not known, research has shown that:

late harvested fruit scalds less than early harvested fruit (within a cultivar)
the riper the fruit at harvest, the less likely they are to scald
scald susceptibility varies from year to year among fruit, even from the same tree
year to year variation in scald susceptibility is a function of weather (at least partly)

As a result of extensive research on scald susceptibility of Delicious apples in New England, UMass researchers Sarah Weis, and Drs. William Bramlage and William J. Lord developed prediction equations for determining scald susceptibility based on:

harvest date
the number of days when minimum temperatures were less than 50 degrees F
the average starch-index at harvest.

These equations proved very reliable for predicting low, intermediate, or high susceptibility of New England Delicious apples to scald in air storage. Therefore, the formula(s) can be used to predict the most efficient use of a DPA scald prevention treatment:

highly susceptible fruit require a 2000 ppm. pre-storage DPA treatment
moderately susceptible fruit require only 500 ppm
low susceptibility fruit need no pre-storage DPA dip

Use the equations below (start with Equation 1) to fine tune yourrequirement for scald-preventive DPA treatments, saving both money and chemical use on stored fruit.

Start here ---> Equation 1: To identify scald-susceptible Delicious fruit (more than 60% likely to scald)

Equation 2: To identify scald-resistant Delicious fruit (less than 20% likely to scald)

Reference: "An Easy and Reliable Procedure for Predicting Scald and DPA Requirement for New England Delicious Apples" Sarah A. Weis, William J. Bramlage, and William J. Lord, Department of Plant and Soil Sciences, University of Massachusetts. Fruit Notes, Volume 63 (Number3), Summer 1998