92 



and lower surfaces of the leaf, the growth of the scab fungus 

 has a tendency to follow the veins. The round spots often 

 become raised on the upper surface, causing a corresponding 

 depression on the lower side. Similar spots, but darker in 

 color, form on the fruit just beneath the waxy outer layer or 

 cuticle. (Fig. 2.) This cuticle soon becomes ruptured over 

 the spots, giving them a scab-like appearance, which suggests 

 the common name of the disease. Cracking of the fruit often 

 accompanies severe infection. (Fig. 2.) 



Scab does not in itself cause rotting of the fruit, but in 

 storage other fungi may gain entrance to the flesh of the fruit 

 through the scab lesions and set up decay. These are discussed 

 under "Storage Rots." 



Black-Rot. 



Authorities differ as to the importance of black-rot. With- 

 out question, however, this disease is the cause of considerable 

 loss in Massachusetts, and in the eastern part of the State it 

 is second only to scab in importance. 



The cause of black-rot is a fungus, Physalospora cydoniw. 

 This fungus gains entrance to the flesh, causing it to decay. 

 Usually a single decayed area is produced which spreads until 

 the entire apple is involved. In the early stages of decay the 

 spot is brown, often marked by zones or rings, and after a 

 time the sm'face of the spot becomes dotted with minute black 

 pimples under which are the fruiting bodies of the fungus. 

 The rotted area eventually turns black, whence the name. In 

 the later stages of decay, fruit affected with this disease be- 

 comes wrinkled and finally shrinks into dry, hard mummies. 

 (Fig. 3.) 



Any part of the fruit may be attacked by black-rot, but it 

 most often starts at a wormhole or at the calyx end. In the 

 latter case, it is sometimes called blossom-end rot. (Fig. 4.) 

 Blossom-end rot frequently may be traced to spray injury in- 

 curred at the time of the so-called calyx spray, when the 

 • nectaries of the blossoms are exposed and easily burned by the 

 spray materials. 



Characteristic brown spots are produced on the leaves by 

 the black-rot fungus. (Fig. 5.) 



