12 MASS. EXPERIMENT STATION BULLETIN 183. 



Only roses under glass are known to be affected. Some varieties, e.g., 

 Hoosier Beauty, are more susceptible than others, but there is yet no 

 evidence that any are immune. Massey (1917) observed the disease on 

 Hoosier Beauty, Ophelia, Hadley, Russell, Sunburst, American Beauty 

 and many seedlings. It has been reported only from the northern and 

 eastern United States, but closer observation will probably show that 

 it has a much wider range. 



SYMPTOMS. 



The disease is most easily recognized by brown dead areas (cankers) 

 in the bark of the stems. These are more frequent and larger at the 

 crown than higher up, but any part of the stem or branches may be at- 

 tacked. Crown cankers may be below the surface, just at the surface, 

 or, more often, extending up the stem, sometimes several inches (Plate I., 

 Fig. 1). They may be confined to one side or may girdle the stem. The 

 young canker is blue-black or purplish in color and smooth, but as it 

 becomes older the part above ground becomes reddish brown, dry, hard 

 and cracked longitudinally. The margin is definite, and the dead area 

 becomes sunken. Frequently the part of the stem immediately above 

 the canker is swollen (Plate II.). When the subterranean part of the 

 canker becomes old it is soaked and "punky," and the bark may be 

 rubbed off between the thumb and forefinger, or it may rot away entirely 

 "(Plate I., Fig. 1). Sometimes a callus is formed around the edge of the 

 canker. 



Two types of cankers occur on the stem and branches higher up. The 

 larger ones start from wounds, especially the stubs which are left after 

 the blossoms are cut (Plate I., Fig. 2). Cankers from these stubs run 

 back down the stems. The canker may stop at the first live branch 

 below, but very commonly it continues to progress downward, and each 

 successive branch dies as it is encircled by the descending canker. Can- 

 kers may also start from other wounds besides cut stubs. They are 

 usually oval in outline and may be several inches long. The second type 

 of aerial canker does not originate with wounds, but starts directly in 

 the healthy green bark. First, small round purple areas appear, some- 

 times singly but more often in groups. As these increase in size the cen- 

 ters become light brown and the margins remain dark, giving a "bird's- 

 eye" effect. When they occur in groups they coalesce and form large 

 irregular dead areas in which, however, the individual cankers may still 

 be distinguished for some time (Plate III., Fig. 2). 



The depth of the canker varies, depending on such factors as the age 

 of the part attacked, size of the infection court, environmental condi- 

 tions and probably others. This is particularly a disease of the bark, 

 and commonly the discolored area will be located outside the cambium 

 entirely. But in more severe cankers it may extend to, or entirely through, 

 the pith. If the shoot is young and has not yet hardened, the canker goes 

 deeper and the entire shoot dies. This is frequently evidenced in the 



