margin caused by the drawing away of the diseased bark from 

 the healthy tissue. This differs from the Sphaeropsis canker in 

 that the surface is smooth, the only cracks being those which 

 mark the extent to which the canker has spread in a given 

 period of activity. The Blight Canker is always of a brown 

 color and never shows any fruit bodies, except when it is old 

 and the dead tissues have been attacked by rot fungi. Some- 

 times these cankers kill a limb, but frequently the disease does 

 not extend thru the bark into the wood, except in a few places. 

 It simply kills the outer porlion of the bark (Fig. r>). 



In the Xew York Apple Tree canker, the fungus lives from 

 year to year, gradually spreading so' as to involve a large portion 

 of the limb, but the Blight cankers are for the most part annual, 

 living only one year. Only a small percentage of Blight cankers 

 live 1 thru the winter and serve as infection sources for the spread 

 of the disease the following year. 



FORMS OF THE CANKER OX DIFFERENT PARTS OF THE TREE. 



The chief differences between these two cankers are set forth 

 in the following parallel columns : 



NEW YORK AITLiE TREE CANKER. BLIGHT CANKER. 



Caused by a fungus. Caused by bacteria. 



Usually found on the main Occurring most frequently on 

 limbs of old trees. the body and limbs of young 



trees jusl coming into bear- 

 ing. 



Diseased portion more or less Diseased area sunken and 

 swollen, cracked and rough- smooth not cracked and 



ened. (Fig. ."!). checked. (Fig. 7). 



Cankered surface black. Cankered surface brown. 



Covered with minute black pirn- Not showing any pimples or 

 pies — the fruit bodies of the fungus fruit bodies, except in 



fungus often not so evident old cankers that have been 



in old cankers. (Fig. 3). invaded by saprophytic 



forms. 



Freshly cankered tissue dry. Freshly cankered I issue watery. 



(Jankers perennial, i. e., living A large per cent, of the cankers 

 over and spreading from year arlive but one season, 



to year. • 



