SPRAYING EXPERIMENTS AND APPLE DISEASES. 21 



While the branches were frequently affected near the tip, in 

 many cases the diseased area began one or 2 or even 3 inches 

 back on last year's growth and extended back from one to 

 several inches. The bark on the diseased portion of such 

 branches was more or less thickly studded with light brown 

 spots. Scattered spots were, as a rule, oval to elongate in 

 shape, although frequently nearly circular, and were usually 

 not much larger than a pin-head. Quite often in severe cases 

 these spots ran together, forming a diseased patch of consider- 

 able area which appeared as a scurfy coating on the bark. 



Closer examination of the light brown spots showed that they 

 were blister-like pustules resulting from the death and pushing 

 out of the epidermis or outer layer of the young bark. Tn the 

 center of each pustule was a blackish portion composed of the 

 olive-colored conidia or spores of the fungus. 



A detailed study of the conditions in the field was made by 

 Mr. Darrow in the vicinity of Orono. This was of necessity 

 somewhat limited, as the location is outside of the best apple 

 growing district of the state. It was observed that strong- 

 growing water sprouts were more badly afTected than young 

 growth on the ends of branches. Water sprouts 2 or 3 feet 

 long were often diseased for the last foot or more of their 

 growth. Also the more vigorous growing twigs at the ends of 

 the branches were the more severely attacked. Those which 

 showed but little elongation were only slightly infested, or not 

 at all. 



In an orchard containing seven varieties, Mcintosh and Fam- 

 euse were the worst attacked. Milden and Westfield ranked 

 next in order of susceptibility. Only an occasional twig was 

 found to be affected on the Northern Spy trees and these but 

 slightly, while the Oldenburg and Tolman trees were entirely 

 free from injury. 



Many oi the spores of the scab fungus, found in the pus- 

 tules already mentioned, germinated readily when placed in 

 proper culture media or even in water. These germinations 

 were made at various times during the latter part of the win- 

 ter and spring up to about the first of May. No exact data 

 was secured to determine whether the spores so germinated 

 were those formed the fall before or those which had been 



