Dec, 1909.] 



SOME APPLE DISEASES. 



113 



The majority of the scab infections are made early in the 

 season, but there is often a second spread of the disease in 

 August. The young scab spots on the fruit at gathering time 

 are evidence of this late attack. They do not, however, show 

 the total amount of damage done by a late spread of the disease, 

 as young scab colonies may continue to develop in storage and 

 unsprayed apples apparently free from scab may develop the 

 disease in storage if taken from an orchard in which a late 

 spread of scab occurred. These scab spots that develop in stor- 

 age must have their origin either from colonies that were too small 

 to be noticed at the time of picking or from spores carried 

 into the barrel 

 with the fruit. 



The scab 

 fungus, like 

 most other 

 plants, is greatly 

 checked in its 

 growth by low 

 temp eratures. 

 Its greatest de- 

 velopment n 

 stored fruit can 

 therefore be ex- 

 pected in bar- 

 rels from cellar 

 storage or which 



were delayed in reaching the cold storage plant. In some sea- 

 sons there has been considerable loss from the development of 

 scab on cold storage apples. 



One familiar with the disease as it occurs in the orchard is 

 inclined at first sight to call the storage trouble a separate and 

 distinct disease (Fig. 3). The fungus makes an unusual de- 

 velopment beneath the cuticle before breaking thru and the 

 mycelium is very dark in color. Consequently black, sunken 

 spots develop on the apple and sometimes attain a diameter of 

 one quarter of an inch before any break is evident in the skin 

 (Fig. 4). The cuticle is finally ruptured and the usual form 

 of spore and sporophore exposed (Fig. 5). 



Fig. 3.— Scab on cold storage apple. 



