This is the fourth report* of the apple storage investigations begun in 1906 by the Pomology Section of the Iowa Agricultural Experiment Station. The report embodies the results of investigations dealing mainly with the development and control of such storage diseases as Jonathan-spot, apple-scald and internal breakdown. The investigations are divided into two parts. Part I deals with the development and control of the storage diseases, Jonathan-spot and soft-scald on the Jonathan apple. Part II includes studies on the development and control of apple-scald and internal breakdown and the effect of certain odorous substances on apples.

The report embodies the results of investigations on the keeping quality of apples in storage as affected by varying treatments in the orchard, as time of picking, time of storing and soil cultural methods. Various storage conditions such as temperature, humidity, and aeration have been considered. Particular attention has been given to different types of apple wraps. The keeping quality of Jonathan apples has been compared in cold and common storage.