DISEASES OF THE PLUM 1199 



diseased fruits may be distinguished 1'wni the healthy fruit by 

 their pale yellow color. Later, the affected plums become coated 

 over with a tine powdery substance; this consists of the spores of 

 the causal fungus. Finally, the diseased fruits turn black and 

 fall. The further history and function of the spores mentioned 

 above is not well known. 



The disease is local in nature. It may attack a single tree, 

 every plum on the tree bearing pockets, while surrounding 

 trees remain unaffected. A tree once affected continues to bear 

 pockets in succeeding years, if weather conditions .are favorable. 

 Some claim that this is evidence that the fungus hibernates in 

 the twigs and that infection in the spring is accomplished by the 

 resumption of growth of the fungus. 



Control measures consist in spraying before the buds open with 

 bordeaux mixture 4-4-50, or lime-sulphur 1-15. 



