60 EXPERIMENT STATION RECUKD. 



nation, show a much roughened and thickened bark, and in many 

 instances a portion of the wood is laid bare. The dead bark on many 

 diseased limbs clings tenaciously to the decaying wood, which is a 

 feature that distinguishes this canker from sun scald. The area of 

 bare wood is often small as compared with the extent of swollen bark. 

 The progress of the disease is marked hy numerous pits and scars, 

 showing M'here the fungus was al)le to live until it gained entrance to 

 the caml)ium through some injury. The scars are usualW circular in 

 form and ma}" be outlined by 2 or more concentric lines. The fungus 

 shows a preference for the larger limbs of mature trees, although the 

 trunks and branches of young trees, as well as the small limbs and 

 twigs of a current season's growth, suffer from its attack. While the 

 extent of injury done to the orchards can scarcely be estimated, it is 

 the author's belief that it is one of the worst diseases which the 

 orchardist will have to contend with, since it attacks the tree directly 

 instead of the foliage. 



Infection, it is stated, takes place in the spring of the year, and the 

 presence of the fungus is indicated in a newly-infected limb by the 

 appearance of a small area of discolored bark. This area extends 

 slowly as the fungus grows outward until midsummer, when a definite 

 boundary forms l)etween the dead and living bark. The season's 

 growth is stopped by the 1st of August, and in some instances pyc- 

 nidia containing mature spores were found at that time. The myce- 

 lium was unable to penetrate to the caml)ium through the living l)ark, 

 but those spores which chanced to fall and germinate in a wound pro- 

 duced the cankers. There is some evidence that the mycelium lives 

 over winter and continues its growth the following spring. 



Among preventive measures, the author recommends that special 

 attention should be paid to the sanitary condition of the trees. The 

 practice of scraping and whitewashing the trunks, now largely in dis- 

 favor, is recommended for adoption in localities where canker is severe; 

 also washing the trees with a whale-oil soap mixture, spraying with 

 Bordeaux mixture, cutting out cankered limbs, and covering the 

 wounds witli Bordeaux mixture or some other fungicide. The time 

 for spra3dng is given, the first application to be made at the time that 

 the leaf buds begin to open, a second a week before the blossom buds 

 open, a third as soon as all the blossoms have fallen, and a fourth 10 

 da3^s or 2 Aveeks later. 



The investigations of this disease were continued in 1899, and it was 

 found that a numb.er of fruit trees are attacked l)y species of Sphte- 

 ropsis. The author's investigation would seem to indicate that the 

 number of species can bo materially reduced, since there is great proba- 

 bility of the same species occurring in a slightly modified form upon 

 a numbci- of hosts. 



