Apr. IS, I9IS Apple Bitter -Rot 6i 



winter stage of the fungus will explain why the rot is apt to recur on the trees affected 

 the year before with the bitter rot, and also why the disease should first appear on 

 such trees. The cankers produce spores early in the season, and from the trees which 

 have cankers the disease spreads to neighboring trees. * * * n ^ow seems 

 probable that the mummies play a comparatively small part in serving as distributing 

 points for spores from year to year. 



Alwood (1902, pp. 264-265, 270), after extensive investigations of the 

 disease in Virginia, states: 



Diligent search of the limbs failed to show any bitter-rot cankers on these [suscep- 

 tible] varieties mentioned. * * * In no instance have we been able to find the 

 presence of the bitter-rot fungus on the limbs or trunks of apple or pear, though we 

 have especially watched for its occxurence since the appearance of the publication 

 cited [Burrill and Blair]. - * - It appears to be well established that the mum- 

 mied fruits hanging to the trees and the rotted fruits upon the soil constitute in a 

 large measure the source of tlie annually recurring infection. 



Scott (1906, p. 12), after investigating the disease in Virginia, agrees 

 with Alwood in that he considers mummies as the chief sources of infec- 

 tion. He states: 



The results lead to the conclusion that the overwintering mummies hanging on 

 the trees constitute the chief source of infection, at least in tliis particular region. 

 In the majority of cases examined a mummy could be found in the upper portion of 

 the infected area, but in no case was there found associated with such outbreaks any 

 cankers that could be identified as bitter-rot cankers. 



Shear and Wood (191 3, p. 76) obtained Glomerella cingulata from a 

 great variety of plants, and it is possible that in some cases early infections 

 may come from hosts other than the apple. 



INVESTIGATIONS IN THR OZARKS 



The large number of primary infections in some of the orchards of the 

 Ozarks from which mummies had been practically all removed and in 

 which the bitter-rot cankers as described by previous writers were few or 

 wanting led the writer to undertake to discover from what sources the 

 early infections were arising in such serious abundance. It was impos- 

 sible to believe that mummies and bitter-rot cankers, so few in themselves, 

 could be the sole harboring places of a fungus which could cause from 10 

 to 200 rotten spots to appear on nearly every apple on large, heavily 

 laden trees. 



In this region cankers and dead areas on limbs, due to various causes, 

 are very abundant. The Illinois apple-tree canker, caused by Num- 

 mularia discreta, is a very prevalent and serious disease. Cankers and 

 dead areas due to Bacillus amylovorus, Phyllosticta soliiaria, and various 

 physiological and mechanical causes are also quite numerous. In some 

 of the orchards it is almost impossible to find a branch or twig which 

 does not show several of the cankers caused by P. soliiaria. 



Considering these cankers as possible sources of early infections, all 

 cankers and dead wood, in so far as practicable, were removed in the 



