Investigation of Rose Diseases 
By Dr. L. M. Massey, New York. 
A SPECIAL and extensive investigation of the dis- 
eases of roses has been undertaken by the De- 
partment of Plant Pathology, Cornell University. 
This work, which was begun August 1, 1916, is being 
•conducted in co-operation with the American Rose" So- 
ciety, whose members have contributed towards the 
financial support of the undertaking. 
During the past three months much time has been 
spent in visiting rose plantings in northeastern United 
States, making a survey of diseases. The gardens and 
greenhouses of some thirty-five rose growers have been 
visited. The number and extent of the diseases present 
have been noted and specimens taken for further study. 
Growers have also materially aided the work by sending 
in specimens. These specimens have been examined, 
and the grower advised as to the cause and control of 
the disease so far as our present knowledge and ex- 
perience allow. 
Unfortunately, nothing is known concerning the con- 
trol of many diseases of the rose, and but little concern- 
ing even some of the most common diseases ; and what 
little is known is mostly of an academic rather than of 
a practical nature and not accessible to the average 
grower. Every grower who has endeavored to obtain 
much information upon any rose disease has been 
brought face to face with this unfortunate situation. 
It is for the correction of this condition that members 
of the American Rose Society have enlisted the services 
of a plant pathologist to investigate rose diseases and 
place the information before the growers. 
The preliminary survey has shown that the two most 
common diseases of the rose are the powdery mildew 
and the black spot, both on indoor and outdoor plants. 
These diseases have received the most attention of 
growers and plant pathologists in the past. It has been 
proved beyond doubt that they are caused by fungi ; the 
life-histories of the causal organisms have been partially 
worked out. and various suggestions for control offered. 
Considerable work remains to be done to determine the 
conditions which favor the development of these diseases 
and the best methods of treatment. It is the plan of the 
writer to publish a short article in the trade papers in 
the near future upon each of these diseases in which the 
known facts concerning them will be placed before the 
growers. 
However, the survey has revealed the fact that other 
diseases besides mildew and black spot cause rose grow- 
ers considerable losses. In fact, many greenhouse men 
claim that these two diseases cause them little worry. 
Ophelia and American Beauty plants affected with a 
serious root or crown -rot have been received from 
growers and observed by the writer, in visits to rose 
houses. The plant decays just below the surface of the 
soil, usually where the plant "breaks," the developing 
branches being encircled by the rot. Soon the parts of 
the plant above ground become yellow and of a sickly 
appearance as if starved for moisture or food, and die, 
a more or less lingering death. Some growers have 
kindly furnished samples of plants so affected, and sev- 
eral organisms which may possibly be causing the dis- 
ease have been isolated from diseased tissue. Inocula- 
tions will be made to determine which organism is the 
cause. The life-history of the pathogene will be studied 
and an attempt made to work out some method of con- 
trol. This is necessarilv a slow process but will, we 
trust, result in the discovery of an effective means of 
controlling the trouble. 
Other diseases which have been noted are: ( 1) crown 
gall, caused by a bacterial pathogene, affecting the roots 
and occasionally the stems of both indoor and outdoor 
roses; (2) Phyliosticta leaf-spot, affecting outdoor roses, 
chieflv ramblers; (3) other leaf spots and cane diseases 
of unknown causes. Work upon the cause of the dis- 
eases in this last group is now under way. Extensive 
experiments on the control of leaf-spot diseases of in- 
door and outdoor roses are being planned and will be 
tested out as quickly as possible. Reports of progress 
will be made from time to time. 
Some misunderstanding seems to exist among growers 
in regard to sending specimens for examination. Where 
desirable, a postal card will bring to the grower one 
or more franked tags which will carry specimens by 
mail postage free; or the grower may pay the postage 
if he so desires. The specimens will be examined, and 
the sender furnished with all available information re- 
garding the cause and control of the disease. Not only 
members of the American Rose Society, but rose grow- 
ers in general may take advantage of this opportunity 
to obtain information relating to rose troubles. By 
sending specimens the grower will not only help himself, 
but will be materially aiding the project. Specimens 
will always be appreciated, regardless of whether or not 
they are of a new or an old disease, or of economic im- 
portance. It is especially desired at this time to obtain 
rose plants affected with root diseases. 
Address all correspondence to L. M. Massey, Depart- 
ment of Plant Pathologv, Cornell University, Ithaca, 
N. Y. 
Rose Diseases and How to Control Them 
R 
( >SES are subject to a number of fungus growths 
;ausing serious diseases and the gardener must 
ward these off carefully if he would keep his plants 
in the healthful condition necessary for satisfactory 
growth and the production of blossoms. These 
fungus parasites rarely kill the plants outright, ac- 
cording to the U. S. Department of Agriculture, but 
by their presence the vigor of plants is greatly re- 
duced, the foliage may be rendered unsightly, branches 
more or less distorted or disfigured, and the quality 
•of the blossoms lowered. In considering the fungus 
diseases of these plants the fact must be recognized 
that in common with similar diseases of other plants 
treatments are preventive rather than curative. W^hile 
thorough and repeated sprayings with a suitable fungi- 
cide will in most cases so check the development of 
the parasite that the disease for the growing season 
will be in a great measure controlled, the full benefit 
of fungicidal applications can only be secured by their 
early use in the spring, guarding in this way against 
the recurrence of a disease of the previous season. 
Powdery mildew is extremely common, few gar- 
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