84 COMMERCIAL ROSE CULTURE 



BLACK MILDEW 



This is a disease which, fortunately, is little seen on Roses. 

 It causes young, vigorous leaves to suddenly wilt and fall off, 

 the young shoots will droop and die back and, if not checked, 

 the whole plant will become affected. The spread of this dis- 

 ease is very rapid and whole houses are quickly ruined where 

 it has gained a foothold. The general appearance of the foli- 

 age, when affected, is similar to that caused by a very bad dose 

 of red spider. Sulphur, painted on the pipes strong enough to 

 leave a deposit of sulphur on the plants, will eradicate this 

 disease. 



ROSE CANKER 



This may be divided into two parts, and we will first con- 

 sider this disease as found on plants which have been grafted 

 or budded. The cause is an accumulation of food material at 

 the junction of stock and cion induced by the unequal ac- 

 tivity of the same. If the sap is flowing from the stock faster 

 than the cion can use it, or if the opposite is the case, a mori- 

 bund or hidebound condition of the tissues results, and canker 

 or rupture supervenes. We have a very recent illustration of 

 this in the Rose My Maryland and others, which do not al- 

 ways succeed well on Manetti. It is simply because some kinds 

 do not hitch up well together, to use a homely phrase. 



Another form of canker is found on outdoor Roses, com- 

 mencing on wood of the second year's growth, in the form of 

 red patches scattered over the bark. Sometimes little injury re- 

 sults from this other than the seamy appearance of the bark 

 which, later, disappears in warm latitudes. But, where frost is 

 common, the affected parts crack during the Winter. As the 

 bark commences to grow over these cracks to heal the wound, 

 the callus is affected with the disease, and large, rough out- 

 growths of callus are formed. All diseased branches should be 

 removed, and the burned and spotted parts painted with creo- 

 sote. Cabot's creosote is recommended for this purpose? 



