1198 THE FEUIT INDUSTRY IN XEW YOBK STATE 



on the upper side of the leaf. Finally, the foliage may tnrn 

 yellow and fall prematurely. 



It has been determined that the fungus hibernates in the old 

 leaves on the ground. In the spring, when the trees are develop- 

 ing the first new leaves, quantities of spores (in this case, asco- 

 spores) are discharged from specialized organs in the old, fallen 

 leaves. These spores are blown to the new foliage,, where, after 

 a week or ten days, they produce spots. Very soon, on the lower 

 surface of the leaf, the whitish pustules appear as previously de- 

 scribed ; these pustules are masses of summer spores produced by 

 the fungus in the leaf. The spores spread the fungus through- 

 out the summer, resulting in a wide distribution of the disease. 



Bordeaux mixture at 5550 or lime-sulphur solution 150 may 

 be used for the control of this disease, although the former often 

 causes burning of plum foliage. Since infections begin with the 

 appearance of the first leaves in the spring, the first spraying 

 should be made about ten days after the blossoms fall. Destruc- 

 tion of cH leaves, which harbor the fungus from the previous year, 

 is a measure in itself unreliable, but, of course, is good practice 

 supplemented by spraying. 



PLUM POCKETS 



Plum pockets, or plum bladder, cause by Exoascus Pruni 

 Fuckel, is a name which arises from the peculiar pocketlike or 

 bloated appearance of affected plums (Fig. 397). The trouble is 

 caused by a fungus closely allied to that causing peach leaf curl. 

 The disease is not very prevalent and most injurious when the 

 spring is col'd and damp. It is therefore erroneously believed to 

 be due to cold, humid weather; but, as stated above, a fungus is 

 the direct cause. 



The fungus attacks the plum at ian early stage of growth, either 

 while yet a fruit bud or soon after the blossoms fall. The in- 

 vaded tissue of the incipient fruit is stimulated by the fungus 

 doubtless by some slightly poisonous secretion, and the result i; 

 the production of an abundant spongy growth until the whole 

 form of the plum is enlarged and distorted. In reality, the pul] 

 and stone of the fruit are replaced by a thin, soft, inflated shell 

 and in place of the seed there exists merely a hollow cavity. Th< 



