New York Agricultueal Experiment Station. 343 



regarded usually by them as being the result of sun scald, or as 

 a condition peculiar to the growth of certain varieties of apple 

 trees. It was only necessarj^, however, to call the attention of 

 orchardists to the disease and to make known its appearance 

 and effect, when it was recognized and found to be a serious 

 pest in most of the apple-growing sections of the State. 



While the bulletin above mentioned gives the results of two 

 years' work with the fungus, it is incomplete; since many ques- 

 tions arose that could not be answered. The work was con- 

 tinued through the season of 1900 and a few more facts were 

 established which add to our knowledge of the disease. 



EFFECTS OF THE DISEASE AND APPEARANCE OF 



AFFECTED PARTS. 



A brief discussion of the work of the fungus and the appear- 

 ance of cankered limbs will not be out of place at this time; but 

 for a fuller discussion of the subject the reader is referred to the 

 former bulletin. 



Any part of the trees above ground, with the possible exception 

 of the leaves, may be attacked by the canker fungus which has 

 been proven to be SijJiwropsis maloi'um Pk. When the larger 

 limbs, or in rarer instances, the trunks, are attacked, the inju- 

 ries are known as cankers. Such injuries are often quite con- 

 spicuous since the bark becomes thick and rough, and saprophytic 

 fungi soon gain a foothold causing the parts to turn black. (See 

 Plate LIII.) The injuries are often several feet in length; and 

 because of these striking characters, cankered limbs may be 

 recognized at a considerable distance. 



The fungus may live in the outer bark, but here it does little 

 harm, and true cankers are formed only when it gains entrance 

 to the cambium layer. Under favorable conditions the fungus 

 spreads until a considerable area of bark is destroyed. The limb 

 may be girdled by the fungus, but borers and saprophytic fungi 

 often complete the work of destruction. An affected branch 

 may live for a number of years and bear fruit, but if the wound 



