Dec. i6, 1918 Brown Canker of Roses 599 



single year that the disease has been under observation were negative. 

 From the present knowledge of this rose canker and its causal fungus, 

 together with the control measures employed for diseases of a similar 

 nature, certain preventive methods are suggested. Rose gardens should 

 be carefully inspected to determine whether the disease is present and 

 precautions taken to prevent the entrance of the fungus into healthy gar- 

 dens. Nursery stock for planting should be carefully examined, and all 

 cankered plants should be destroyed. If possible, plants should be intro- 

 duced only from gardens known to be free from the disease. In gardens 

 where the canker is already established, measures leading to the eradi- 

 cation of the fungus should be adopted. Cankered stems should be cut 

 away and burned. It may be advisable to disinfect the cut ends of the 

 stems and to sterilize the pruning implements after each operation. 

 The use of a fungicide to protect the plants from further infection is sug- 

 gested. In the fall after the plants have become dormant and again early 

 in the spring strong Bordeaux mixture ^ may be applied. It is probably 

 important that the plants be well covered with the fungicide during the 

 early spring months when the lesions first appear and the disease makes 

 rapid progress. Gardens should be carefully watched in the spring in 

 order that stems showing infection may be cut away and not become 

 sources of secondary infection. As blossoming time approaches, ammo- 

 niacal copper carbonate may be substituted for the Bordeaux mixture, 

 as it does not discolor the foliage. A complete study of the varieties 

 resistant to this canker has not been made, but, as stated in the intro- 

 duction of this paper, in the National Rose Test Garden, where most 

 classes of cultivated roses are represented, the brier roses, the rugosa 

 roses, the moss roses, some of the ramblers, and most of the named 

 species are apparently resistant. 



SUMMARY 



(i) A canker of roses caused by the fungus Diaportlie umbrina is 

 probably widely distributed and is known to occur in the District of 

 Columbia, Virginia, West Virginia, Georgia, and Connecticut, having 

 been reported at various times during the past 15 years. 



(2) The causal organism produces in cankers on living rose stems a 

 pycnidial and a perfect stage. 



(3) In culture both the pycnidial and perithecial stages of the fungus 

 have developed. 



(4) The disease has been produced on rose stems from both pycno- 

 sporic and ascosporic stages of the fungus. 



(5) The control measures suggested are the use of only healthy nursery 

 stock for planting, the removal and burning of diseased canes from 

 affected gardens, and the application of a fungicide in the fall, again in 

 spring before the first symptoms appear, and during the spring when the 

 fungus is active. 



' For directions for the preparation and application of fungicides for rose diseases see Mulvord, F. L,-, 

 ROSES FOR THE HOME. U. S. Dept. Agr. Fanners' Bui. 750, 36 p., 37 fig. 1916. 



