BULLETIN No. 183. 



DEPARTMENT OF BOTANY. 



ROSE CANKER AND ITS CONTROL. 



BY P. J. ANDERSON. 



INTRODUCTION. 



Rose canker is a serious disease of greenhouse roses which was first 

 described in 1917. It has probably been long prevalent in America, but 

 has escaped notice largely on account of its obscure symptoms and con- 

 sequent difficulty of diagnosis. Its ravages were formerly assigned to 

 other causes or left unexplained. Rose growers who first brought it to 

 the attention of this station in November, 1916, stated that they had 

 been suffering severe losses for at least four years. After conditions in 

 the rose houses had been investigated, the situation was considered so 

 serious that work was immediately begun to determine more of the nature 

 of the disease, and especially to find a remedy for it. The investigation 

 was started in co-operation with L. M. Massey, pathologist of the Ameri- 

 can Rose Society, who first observed the disease two months before this, 

 and had already decided that its seriousness warranted a thorough inves- 

 tigation. Research at the Massachusetts station has been largely confined 

 to determination of the best methods of controlling the disease and inves- 

 tigation of such facts in the life history of the causal fungus as have a 

 direct bearing on control measures. Massey undertook investigation of 

 other phases of the disease, and has recently published his results (1917). 

 A successful method of control has been evolved and is presented in this 

 bulletin, but it is hoped that, as a result of long-term experiments now in 

 progress in commercial houses, this method will be improved and, pos- 

 sibly, other easier methods found. However, since this will require a 

 number of years, the present method is published in order that rose 

 growers who are troubled with the disease may have the benefit of all 

 that we alread}'^ know about canker and its control. 



' The writer is greatly indebted to Prof. A. Vincent Osmun, head of the department of botany 

 at this station, for much valuable assistance, suggestions and criticism of the manuscript of this 

 bulletin. 



