l^EW YoKK Ageicultural Experiment Station. 403 



spots vary in size from small dots to the large irregular patches 

 which are formed when two or more smaller spots coalesce. 

 Where the spots are large the fruit may become one sided or oth- 

 erwise distorted, and often it cracks open. For this reason the 

 disease is sometimes called " the cracking of the apple." 



On the leaves the fungus has the appearance of a dark mold. 

 It is found in spots on both the upper and under surfaces. The 

 disease may cause the leaves to be much crumpled and finally 

 show brown, dead tissue which breaks away leaving the foliage 

 torn and ragged, or the entire leaf may drop off. 



Some varieties are especially susceptible to its attacks, and it is 

 not unusual to see a very large proportion of their fruit badly 

 cracked by it. On the other hand, there are varieties which are 

 generally quite resistant, on which the scab spots increase com- 

 paratively slowly, and the cracking of the fruit is seldom or never 

 seen. 



On the fallen leaves of the previous season, there develop, in 

 the spring, perithecia within which are perfected sj)ores for the 

 propagation of the fungus.^ The fungus is known to begin its 

 attacks very early in the season, for occasionally it may develop 

 sufficiently to be discovered by the naked eye on unopened blos- 

 som buds. In seasons especially favorable to its early develop- 

 ment it has been observed to cause great injury early in the sea- 

 son, destroying the blossoms and the young fruit. In order to 

 control the disease, therefore, it is important to begin treatment 

 early. It must be borne in mind that the treatnient is effective 

 by preventing the germination of the spores rather than by kill- 

 ing the fungus after it has become established either on the foliage 

 or on the fruit. 



Treatment. — The scab may be controlled by proper spraying 

 with Bordeaux mixture. Fortunately these treatments may be 

 combined with others which are advocated by the Entomologist 



2Aderho]d, Dr. Rud. Die Fusicladien unserer Obstbiiume, I. Theil Landw. 

 Jahrbiicher, 25: 880-914, 1896, 



