DISEASES 



213 



through which the fungus can gain entrance. Sun scald injures 

 the trees in such a way as to give an entrance to this fungus. 

 Varieties most susceptible to this canker are the Spitzenburg, 

 Twenty Ounce, Baldwin, Wagener, Greening, and King. Some 

 reports speak of the Tolman Sweet as practically resistant. 



Pruning, scraping, and 

 spraying are the remedies 

 mentioned for the control 

 of this fungus. Good, 

 thrifty trees, well taken 

 care of, are a good insur- 

 ance against its attacks. 



European apple canker 

 (Nectria ditissima). The 

 European apple canker is 

 a common fungus through- 

 out Europe and to a large 

 extent in the eastern and 

 northeastern states. It 

 resembles somewhat the 

 other cankers, but is a 

 perennial and therefore 

 extends its growth each 

 season, while most of the 

 others are probably an- 

 nuals. Besides this, the 

 injured bark often peels 

 off. The fungus first gains 

 entrance through wounds 

 caused by hailstones, poor 

 pruning, carelessness in 



cultivating, etc. The remedy, then, would be to prevent these in- 

 juries, or to protect the wound by applications of good paint or 

 spray mixture, such as Bordeaux or lime-sulphur. 



Blister canker (Nummularia discreta). Although this fungus 

 has not been a serious pest in any particular place, still it has such 

 a wide distribution throughout the United States and Europe that 

 it seems worthy of some consideration. It has sometimes been 



Fig. 94. Limb canker on young twigs 

 (University of Maine) 



