APPLE DISEASES 139 



apparatus has been suggested as a causal factor. It has been 

 acceptably demonstrated that arsenate of lead is not the cause 

 of the Jonathan-spot. Spots are found on unsprayed as well as 

 on sprayed fruits. While the cause is yet somewhat obscure it 

 is known that the spotting is more common subsequent to a 

 dry season. The disease was severe following the dry summers 

 of 1910, 1911 and 1914; while after the relatively wet season of 

 1912 it was less serious. In storage the disease is found most 

 commonly where the fruit is kept in ordinary storage for some 

 time before being placed in cold storage. It also is favored by 

 poor storage ventilation and by improper storage, temperatures. 

 Where a relatively high temperature prevails, spots develop 

 abundantly. Under such conditions the fruit often " sweats " 

 and rapidly respires. Apparently the causal factor comes from 

 an external source and gains entrance through the lenticels and 

 through other small fruit cracks as evidenced by the fact that 

 such points serve as centers of all lesions. Since investigators 

 are not generally agreed as to the causal agent, and since the 

 possibility that two or more diseases are confused under the 

 same name, the cause of Jonathan-spot remains to be further 

 investigated. 



Control. 



Fruits which hang on the tree too long show the disease more 

 commonly than in cases where they are harvested at the proper 

 time. Fruits picked at maturity, rushed to storage, and con- 

 sumed within a few days after removal from cold storage will 

 not develop the disease to any serious extent. Susceptible 

 varieties like the Jonathan are likely to be severely spotted if the 

 apples are withheld from cold storage, or are merely placed in 

 common storage. It has been estimated that the trouble is 

 quadrupled under conditions of cellar storage as opposed to the 

 amount developed in cold storage. In cold storage the spots 

 which do appear are smaller and less conspicuous. It is to be 

 noted, of course, that the cold storage should be properly 

 ventilated and the temperature should be standard (32 Fahr.). 



