'Nbw Yoek Agricultural Experiment Station. 341 



In some instances cankers occur quite uniformly on the south- 

 west side of the trees, thus indicating that they had their origin in 

 injuries produced by sun scald. The work of the fungus may be 

 recognized by the thick rough bark, while the fruiting pustules 

 reveal its presence where it is still or has recently been in an 

 active condition. 



EXTENT OF INJURY. 



The extent of the injury done to the orchards of the State can 

 scarcely be estimated, but it is safe to say that this canker is one 

 of the worst diseases with which the orchardist will have to con- 

 tend since it attacks the tree directly instead of the foliage and 

 fruit as is the case with the majority of our orchard diseases. 

 The appearance of the cankers is such that their injurious nature 

 may not be apparent to the casual observer until his attention is 

 attracted by the shrivelling of the leaves; thus the tree may be 

 ruined before it is realized that anything serious is the matter. 

 In one instance the loss of a large acreage of orchard was due to 

 the attacks of the canker fungiis (see page 333) and in a great 

 many orchards it has done serious damage. 



TIME AND MANNER OF INFECTION. 



Infection takes place in the spring of the year as is shown by 

 the growth that the fungus makes m the bark. The presence of 

 the fungus in a newly infected limb is first indicated by a small 

 area of discolored bark. This area extends slowly as the fungus 

 grows outAvard in all directions till mid-summer, when a definite 

 boundary forms between the dead and living bark, thus showing 

 that growth for the season has stopped. This season's growth had 

 stopped by the first of August, and in some instances pycnidia 

 containing mature spores were found' at that time on bark where 

 infection had taken place in the spring. 



Many of the spores remain in the pycnidia till the following 

 spring, or longer, when they are given off and disseminated. The 

 mycelium is unable to penetrate to the cambium through living 



