10 APPLE BLOTCH IN SOUTHERN ORCHARDS. 



can not be used for this purpose, owing to the difficulty of paring, and 

 is a total loss except where it can be used for vinegar. A large per- 

 centage of the affected fruit drops prematurely, and unless utilized 

 immediately becomes a total loss. 



TWIG CANKERS. 



The fungus attacks fruit spurs, twigs, and rapidly growing shoots, 

 producing characteristic cankers. On fruiting branches these cankers 

 are small and rather inconspicuous, being about one-eighth of an inch 

 wide and one-half an inch or more long. (PI. I, fig. 4.) They first 

 appear as small purple or blackish blotches. As they increase in 

 size they become brown in the center, retaining a purple margin, but 

 may finally become gray. The bark soon cracks around the cankers, 

 especially along the lateral edges. On rapidly growing shoots, par- 

 ticularly water sprouts, the cankers have the same general appearance 

 as on fruiting branches, but are much larger, often measuring an inch 

 or more in length and sometimes girdling the stem. (PL I, fig. 3.) 

 The longitudinal cracks appear not only along the edges but through 

 the cankers, giving them eventually a rough and scurfy appearance. 

 This is especially noticeable on those which are two or three years 

 old. Cankers with spore-bearing pycnidia are first formed on the 

 current year's growth during the summer and fall. The fungus lives 

 over winter in the canker, and during the following spring extends 

 its growth, enlarging the diseased area, and produces new pycnidia 

 on the advancing margin. This growth may continue for several 

 3^ears, as fresh spores have been found on cankers evidently three or 

 four years old. Frequently, however, the canker is cut off from the 

 healthy tissue by cracks, dries up, and later the wound may heal over. 



As a rule these cankers do not materially injure the tree, killing 

 only a few small branches and water sprouts, but in the case of some 

 varieties they are so numerous and extend so rapidly that they kill 

 the large branches, and even the main limbs as well. A block of 

 200 Northwestern Greening trees at Lanagan, Mo., has been practi- 

 cally destroj^ed by this disease. When visited by the writers in the 

 spring of 1907, the fruiting wood, water shoots, and even larger 

 limbs were almost completely covered with cankers, and many of 

 them were girdled, so that the trees presented a very ragged and 

 sickly appearance. (PL II, fig. 1.) So far as the writers have 

 observed, this is the only case in which trees have been killed by the 

 disease, but frequently Missouri, Limbertwig, and Red Astrachan 

 trees become so badly affected that much of the bearing wood is killed 

 and the trees are materially weakened. 



In 1906 Mr. H. W. Gipple, of Bentonville, Ark., called the attention 

 of the writers to a disease which often kills a large percentage of 



