270 



FUNGOUS DISEASES OF PLANTS 



germination of the conidia. The observation has been made 

 (Clinton) that the scab is first seen more abundantly on the lower 

 leaves, and from this the inference is drawn that infection is 

 chiefly as a result of the production of the perfect or Venturia 

 stage on old leaves which have fallen to the ground. The pro- 

 duction of the perfect stage is common when the leaves fall upon 

 sod and are more or less protected by their own number or by 

 being partially covered with grass, etc. 



FIG. 121. VENTURIA POMI, FROM WINTERED LEAVES OF APPLE 



Control. In the agricultural experiment stations of the United 

 States spraying experiments have been quite generally conducted 

 looking toward the prevention of apple and pear scab. Some dif- 

 ferences in treatment have been recommended for regions where 

 climatic relations are diverse, but in general the method of treat- 

 ment is much the same. At least one spraying should be made 

 with strong Bordeaux mixture before blossoming. In California 

 it has been recommended to spray twice before the fruit buds 

 have opened ; this in case of the pear. A second (or third) 

 spraying may be given immediately after the petals fall, and at 



