DISEASES OF THE CHERRY 



LEX R. HESLER 

 Assistant Professor of Plant Pathology, Cornell University, Ithaca, X. Y. 



Powdery mildew, caused by Podosphaera oxyacanthae (De (V) 

 De Bary, is found on other plants besides the cherry, such as the 

 apple, pear, quince, plum, hawthorn, blueberry, and persimmon. 

 It is in the nurseries of Xew York State that destruction runs high, 

 although orchard cherries are often seriously affected. Budded 

 sour cherry stock is said to be the most severly attacked, and yet 

 sweet cherry varieties and mazzard stocks are often troubled. 

 Mildew is usually most prevalent following a. period of heavy 

 rainfall. 



FIG. 375. POWDERY MILDEW ox SOUR CHERRY TWIGS AND LKAVKS: HCAI.T 

 TWIG AT LEFT AND DISEASED TWIG AT RIGHT 



Affected trees are generally recognized by an upward rolling 

 of the foliage; the young shoots and branch tips are also affected 

 (Fig. 375). On the lower surface of the leaves may be seen a tangle 

 of white, feltlike threads of the fungus. With the early develop- 

 ment of the white, feltlike mass, stalks are projected into the 

 air; these bear the summer spores, which are produced in groat 

 numbers and which spread the mildew parasite throughout the 

 summer. By midsummer small black specks may be observed 

 scattered over the felty mass. These specks are the fruiting 



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