339 



SprMviii.t,' for canker is jiracticed ; hut do not uiisiinderstand what is 

 meant. If the organism is establislied then it is lilvely tliat spraying will 

 not be effective, but trees can be protected against infection. It is often 

 stated tliat canker is not found in well managed orchards, Imt this has 

 not been our observation. Even in some of the best cared for orchards 

 we have found the most cankers. In these cases, either the fungus gained 

 entrance to the caml)iuni in only a few instances, or if it did pierce this 

 layer, the limbs were cut off just back of the diseased area and a new 

 shoot allowed to form. 



It has been noticed for a number of yoars that not all varieties are 

 attacked. We have in mind an orchard in which three rows were the 

 Twenty Ounce variety. Other varieties on either side were unaffected. 

 Just why this difference? Is it due to the virulence of the fungus or does 

 it depend upon increased susceptibility of the host, this in turn to be at- 

 tributed to some subtle change in nutrition, soil condition, or some other 

 overlooked factors of environment? Soil conditions were apparently uni- 

 form, so that some more remote factor nuist have contributed to this 

 phenomenon. 



Is it possible to inject into a tree a substance wliicli would render it 

 immune? It is claimed by some that such a thing is possilile. After all, 

 then, just how far is the canker fungus responsilvle for the destruction of 

 the host? ]May not its invasion be the result of changes from some of the 

 causes suggested rather than the direct work of the parasite? The ques- 

 tions are only to be answered by hoping that future investigation will reveal 

 some of these remote, yet interesting, questions to such an extent that 

 economic conditions generally will ]k> l>eneflted. 

 Wahash College, 

 CrawfordsvUlc, Inch, June 1911, 



