Pre-storage Carbon Dioxide Treatments for Control of Apple Scald.

Apple scald is a non-parasitic storage disease that causes great losses to growers and distributors of susceptible varieties. It is believed to be caused by volatile products given off by the fruit (1). Partial remedies for the disease have been known for some time. Delayed picking was suggested by POWELL and FULTON (3) oiled paper wrappers by BROOKS, COOLEY, and FISHER (1), and waxing, and air coniditioningi, by SMOCK and SOUTHWICK (4). Some work has also been donie on control of scald by storing fruits in pure oxygen (3), pure nitrogen (3), pure carbon dioxide (1), and in tightly sealed containers (1, 2) for various periods of time. The trials were made both at the beginning and toward the end of the storage seasoni. The work was done on the assumption that a change in fruit metabolism can be thus induced resulting in eliminiation of the scald causing factors. Some of the treatments prevented scald but were not considered practical. Experiments at Rhode Islanid Agricultural Experiment Station show the possibility of scald control by short exposures of apples to atmospheres of 30 and 60 per cent. of carbon dioxide at the beginning of the storage season. Rhode Island Greening apples were used for the experiment. They were picked on September 1 and 21, 1944. Some of the fruits were treated immediately after picking, others after a month in storage. The treatments made at 320 F. in a storage room partially filled with apples gave most promising results. They consisted of passing a slow stream of air conltaining 30 and 60 per cent. of carbon dioxide through five gallon containers filled with fruit for 3, 6, and 10 days, respectively. The fruits, after the treatments were over, were stored together at 320 F. On January 28, 1945, they were taken out of storage, some of them subjected to a pressure test, and the remainder placed in a room at 65° to 70° F. They were examined for scald a week later. Check fruits picked on September 1 had 78 per eent. scald. Fruit picked at the same time and treated immediately with 30 and 60 per cent. carbon dioxide, respectively, gave 100 per cent. control for the 3-, 6-, and 10-day treatments. Apples treated after a month of storage had from 6 to 24 per cent. scald. Check fruit picked on September 21 had 50 per cent. scald. Immediate and delayed treatments gave satisfactory results with scald ranging from nione to 20 per cent. The flavor of fruit treated at storage temperature was in no case affected adverselv. The treated apples, however, were harder and greener than the check.