2I 4 



THE APPLE 



called the Illinois canker because of its destructive work in that 

 state. Being perennial in habit, it will in time result in the girdling 

 and death of the limb or tree. 



In appearance the blister canker differs greatly from the other 

 cankers described. The area infested by it is only slightly sunken, 

 brownish in color, turning black as if charred, with a mottled 



arrangement of healthy 

 bark and diseased tissue. 

 Later on the seemingly 

 healthy bark dies, and the 

 whole infested area has 

 a highly uneven surface, 

 often cracking and becom- 

 ing very dry. There is a 

 sharp line of demarcation 

 between the infested area 

 and the healthy bark sur- 

 rounding it. 



Pruning out the dis- 

 eased areas will aid in con- 

 trolling this fungus, and 

 since it gains entrance to 

 the tree through wounds, 

 these must be treated as 

 recommended in the case 

 of the other cankers. 



Decay or rot {Polyporus 

 sulphureus). This fungus 

 establishes itself in the de- 

 caying wood of the tree, 

 especially about knot holes, 

 from there gaining entrance to the heartwood and killing the 

 fibers as it progresses. The affected wood at first turns brown, 

 then decays rapidly. In the autumn yellowish or sulphur-colored 

 shelving clusters of the fungus are developed on trunks and 

 limbs of trees. 



Control measures are to protect all wounds with paint or some 

 other material, in order to leave no openings for this pest. Scars 



Fig. 95. Limb canker on older limbs 

 (University of Maine) 



