2000 ppm DPA will be needed. If fewer than 

 20% of fruit scald, the scald severity on 

 individual fruit is generally not as great as in 

 the "over-60%" group, and a DPA/fungicide 

 drench may not be recommended at all. 



Using data from 213 lots of Delicious fruit 

 grown at the University of Massachusetts 

 Horticultural Research Center (Belchertown) 

 (HRC) from 1988 to 1993, equations were 

 generated to place fruit into the above groups. 

 Lots included fruit harvested from 14 

 September to 22 October, with starch scores 

 ranging from 1 to 7. From 3 to 39 preharvest 

 days below 50°F beginning 1 August were 

 recorded. The equations were used in 1995 to 

 attempt identification of scald-susceptible 

 (>60% of fruit) and scald-resistant (<20% of 

 fruit) lots of Delicious apples. Eight harvests 

 were made at the HRC and four harvests were 

 made at each of two other orchards. Equations 

 and results are shown in Figures 1 and 2. 



Overall, the equations were quite effective 

 in identifying those fruit which were especially 



scald susceptible or especially scald resistant. 

 The situations which potentially cause prob- 

 lems are those which are shown as x's in 

 Figures 1 and 2. Predicting less than 60% 

 (Figure 1) or less than 20% (Figure 2) scald 

 when more actually occurred could result in 

 undertreatment of fruit and subsequent fruit 

 loss. Savings could be made for the lots which 

 are shown in white, as these fruit could receive 

 less DPA than the standard treatment. This 

 possibility was examined in a further study 

 described below. 



The fruit lots used to generate and test the 

 equations above received no postharvest 

 treatment, and were kept in cold storage for 20 

 to 25 weeks after harvest, then at room 

 temperature, about 70°F, for a week before 

 being rated for presence of superficial scald. 

 However, additional fruit were harvested in 

 1995 from the HRC and from Orchard 2 in 

 Wilbraham. These fruit were dipped in 500, 

 1000, 1500, or 2000 ppm DPA, stored, and scald 

 rated along with the other fruit. Figure 3 shows 



O 

 (0 



O 



100 



80 



> 20% Scald, prediction wrong 



< 20% Scald, prediction wrong 



< 20% Scald, as predicted 



> 20%. Scald, as predicted 



P<XXXXXXXXXXXXX>| 



HRC 



Orchard 2 Orchard 3 



Overall 



Figure 2. Predicting reduced scald (<20% of fruit) on Delicious, 1995. Equation was 

 developed from data collected at the University of Massachusetts Horticultural Research 

 Center, 1988-93. If [-11.8 + 0.41(day#) - 0.030(days , 50"F) - O.VKstarch score)) > 0, then 

 it is predicted that < 20% of the fruit will scald. 



Fruit Notes, V<.lunu- 61 (Number 4), Fall, 1996 



