BLUE MOLD DECAY OF DELICIOUS APPLES 3 



standardized bruises were produced throughout these experiments by 

 pressing a cheek of each apple by hand on the platform of scales 

 that had been preset either at 40 pounds for a slight bruise or at 75 

 pounds for a severe bruise. When the pressure exerted on the plat- 

 form deflected the weight arm, the pressure was released. In this 

 manner, uniform flat-surface bruises were made that did not visibly 

 rupture the skin. 



Two bruises were produced on each apple in all of the experiments. 

 A few minutes after bruising, two measurements of the bruise diam- 

 eter were taken at right angles to each other, and the average of the 

 two was considered the bruise diameter. Only severe bruises were 

 produced on the test fruit in 1948 and 1949. 



Inoculating was done by dipping fruit for 10 seconds in a blue mold 

 suspension prepared by stirring 3 to 5 (constant number for each 

 experiment) 1 -week-old petri plate cultures of blue mold in a Waring 

 blender with a little tap water. This mixture was made up to 16 

 liters with tap water in the dip tank. Unless specifically stated 

 otherwise, the test fruit was inoculated within 1 hour after it was 

 bruised. In 1947 inoculated fruits were held 24 hours at ordinary room 

 temperature before they were returned to cold storage at 31° F., 

 but in 1948 and 1949 the holding period at room temperature was 48 

 hours. Inspections of bruised and inoculated apples began after a 

 30-day cold-storage period and were repeated at 4 biweekly intervals. 



To study the rate of enlargement of decaying areas, apples were 

 punctured with a blunt instrument that made uniform injuries % 

 inch deep and Ke inch in diameter. As soon as each lot of fruits was 

 punctured, it was inoculated as previously described, held at room 

 temperature for a period to allow infection to occur, and then placed 

 in storage at 31° F. In 1947 the period at room temperature was 

 24 hours, and decay diameters were measured after 15, 25, and 55 days 

 of storage. In 1948 the incubation period was 48 hours, and de- 

 cayed areas were measured at weekly intervals after the first 10 days 

 of storage. Decay diameters were measured in the same manner as 

 bruise diameters. 



Fruit firmness was determined with a Magness-Taylor pressure 

 tester, using a %6-mch plunger. Readings were taken on 3 pared sur- 

 faces of each apple in 10 fruit samples. 



The influence of cooling rate and cold-storage temperature on 

 decay infection at bruises was studied in 1949 by bruising and inocu- 

 lating about half the fruits in each of three packed boxes of Delicious 

 apples (size 72). The unbruised, uninoculated fruits in each box 

 constituted the checks. A Ryan thermograph was placed in the 

 center of each box of fruit. One box was placed in storage at 31° F. 

 at the laboratory and the remaining two were put in commercial 

 apple-storage plants within 3 hours. All boxes were placed in ex- 

 posed locations to insure maximum cooling. After 29 days the 

 boxes were removed from the commercial plants and brought to the 

 laboratory, where all three were inspected for decay. All the boxes 

 were then held in the laboratory cold storage for 8 weeks, during which 

 period they were reinspected at biweekly intervals. 



