MARKET DISEASES OF FRUITS AND VEGETABLES 49 



there is considerable variation, the lesions of bull's-eye rot are 

 usually larger and paler. If the bull's-eye rot spots are large, the 

 causal fungus may be fruiting on them. They are fairly firm and 

 do not separate readily from the healthy tissue; in cross section 

 bull's-eye rot is found to penetrate toward the core in a U-shaped 

 pattern. 



CAUSAL FACTORS 



The fungus Phialophora malorum, which causes side rot of 

 apple, is primarily a saprophyte living in surface soil and upon 

 the bark and in cankerous woody tissues of apple trees. Apples 

 become contaminated while on the trees, and under favorable 

 conditions the fungus develops and causes serious and unpre- 

 dictable losses in fruit in storage. Most lesions occurring on 

 apples appear to develop around lenticels, but it is difficult to 

 determine in many cases whether the point of entrance was a 

 lenticel or a cuticular crack. The fungus enters also through 

 insect injuries and mechanical punctures. Side rot may appear 

 as early as January in cold storage, developing on bruised areas. 

 It does not become serious on unbruised tissues until later in the 

 storage season; it may be found in considerable abundance at 

 the time the fruit is removed from cold storage. The size and 

 number of the lesions and the number of fruits infected may be 

 expected to increase rapidly after the fruit has been out of 

 storage for a few days. The development of decay in storage and 

 on the market is the result of spores that are present on the 

 apples at harvest. 



CONTROL MEASURES 



The causal fungus has difficulty in establishing itself and caus- 

 ing decay except in bruised tissue and in tissue weakened to a 

 certain point by natural aging. At present no satisfactory control 

 measures such as spraying or disinfection have been found. The 

 rot can be greatly reduced, however, through careful handling 

 of the fruit to prevent undue bruising and mechanical injury and 

 through prompt storing and cooling down to cold-storage tempera- 

 tures. 



The rot has been known to develop much more seriously in 

 fruits in some orchards than in others. The difference is thought 

 to be associated with the degree of maturity of the fruit when 

 harvested and with the rate at which the fruit ripens and weakens 

 in cold storage. Where fruit is definitely known to develop an 

 unusual amount of side rot in storage, it would probably be well 

 to market it earlier than that which remains sound longer. 



(See 80.) 



Skin and Flesh Cracking 



Under this general heading are included cracking in certain 

 varieties of apples due to weather conditions and also skin crack- 

 ing due to washing injuries in the preparation of the fruit lor 

 packing. 



RAIN CRACKING 



Rain cracking occurs most seriously on Stayman, Wealthy, and 

 York Imperial apples grown in humid districts. In the same lo- 



