214 Bl'LI-ETIX 236. 



Fcrtilizuig. — The abundant application of nitrogenous manures also 

 results in rapid and excessive growth. The tissue does not ripen promptly 

 and so affords conditions favorable to the blight. Certain growers say 

 that they can prevent the ravages of blight by the use of phosphates, 

 either bone meal or some form of phosphoric acid and potash. They 

 do not use stable manure. They point out that the phosphates cause the 

 new growths to ripen c[uickly. 



Rot fungi. — In the first part of this bulletin, I have pointed out 

 that the wounds resulting from the formation of the cankers afford in- 

 fection courts for the entrance of decay-inducing fungi. The dead bark 

 affords a most suitable food supply on wdiich the fungus can feed in the 

 first stages of its germination and growth. It serves, moreover, as a 

 sponge in the retention of the moisture necessary for the further de- 

 velopment of the fungus and its entrance into tlie wood of the tree. If 

 the canker has been formed about the base of a blighted watersprout, the 

 dead tissue of the shoot affords a direct entrance for the decay fungus 

 to the heartwood of the tree. Once in the heartwood, the mycelium 

 spreads rapidly through the lifeless tissue, causing it to rot. It also 

 frequently attacks the living sapwood and destroys it also, so that the 

 tree is ruined or even killed outright. The crotches of trees where 

 attacked by the canker serve admirably for the entrance of these rot 

 organisms. The cankers formed about pruned stubs also act as in- 

 fection courts : first, by preventing the prompt and rapid healing of 

 the exposed cut surface ; and second, by affording in the dead tissue of the 

 cankered collr.r, food and moisture for the saprophytic forms. Almost 

 invariably on removing the cankered bark from these stubs, it was found 

 to cover a weft of wdiite mycelium which surrounded and penetrated 

 the dead stub. The heartwood of these diseased stubs had frequently 

 reached that stage of decay that it vv'as soft and watery and was easily 

 removed with a knife blade for a long distance down into the limb. In 

 the Hudson River valley, diseased trees were frequently so heart-rotten 

 that limbs apparently healthy were easily snapped in two, showing only 

 a very thin outer shell of healthy sapwood and bark. 



This matter of the decay fungi that follow the canker is of very con- 

 siderable importance and a factor to be reckoned with in any method of 

 treating the cankered trees. Their relatively early appearance in cankered 

 areas makes it imperative that to secure immunity from their attacks the 

 diseased tissue must be removed as soon as discovered and the wound 

 properly treated and painted over. 



An examination of a number of old cankers will show a large variety 

 of forms of these saprophytes. Many common species of the imperfect 

 as well as ascomycetous fungi will be found. I have also observed various 

 species of the basidiomycetes fruiting in these dead areas. 



