December 2, 1916 



HORTICULTURE 



729 



INVESTIGATION OF ROSE DIS- 

 EASES 



By Dr. L. M. Massey, Specialist on Rose 

 Disease Investigations, Department of 

 Plant Pathology at Cornell University. 



A special and extensive investiga- 

 tion of the diseases of roses has been 

 undertaken by the department of 

 Plant Pathology, Cornell University. 

 This worlv, which was begun August 

 1, 1916, is being conducted in co-opera- 

 tion with the American Rose Society, 

 whose members have contributed to- 

 wards the financial support of the un- 

 dertaking. 



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 vis- 

 ited. 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. Theso 

 specimens have been examined and 

 the growers advised as to the cause 

 and control of the disease so far as 

 our present knowledge and experience 

 allows. 



Unfortunately, nothing is known 

 concerning the control of many (iis- 

 eases of the rose, and but little con- 

 cerning even some of the most com- 

 mon diseases; and what little is known 

 is mostly of an academic rather than 

 of a practical nature and not accessi- 

 ble to the average grower. Every 

 grower who has endeavored to obtain 

 much information upon any rose dis- 

 ease 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 be- 

 fore 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 casual organisms have 

 been partially worked out, and va- 

 rious suggestions for control offered. 

 Considerable work remains to be done 

 to determine the conditions which 

 favor the development of these dis- 

 eases and the best methods of treat- 

 ment. 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. 



STRAWBERRIES UNDER GLASS. 



Strawberries at $2 to $2.50 a pint 

 box in February and :\Iarch should be 

 a paving crop if well managed. Plants 

 in fruit make, also, an acceptable fea- 

 ture in a dinner table decoration from 

 the double standpoint of beauty and 

 utility. The accompanying cut shows 

 a system of strawberry forcing as suc- 

 cessfully carried on by a grower in 

 Waltham. Mass. As will be seen the 

 boxes in which the plants are set are 

 arranged on shelves, one above the 

 other, on the rear wall of a lean-to 

 greenhouse. The boxes are open on 

 top but the plants issue from apertures 



in the front of the boxes and hang 

 towards the light so that the fruit is 

 well exposed to the sun and is also 

 kei)t from injury by contact with the 

 soil. A wooden track runs the length 

 of the house and the man watering or 

 otherwise working on the plants 

 stands on a car which a helper pushes 

 along. Temperature is not allowed to 

 drop" below 6.5 degrees at night and 

 hand fertilizing has to be carefully 

 done to every pistil. Bees are not 

 enough for this and without hand work 

 every sunny day, misshapen fruit is 

 sure to occur. 



However, the survey has revealed 

 the fact that other diseases besides 

 mildew and black spot cause rose 

 growers considerable losses. In fact, 

 many greenhouse men claim that these 

 two diseases cause them little wor- 

 ry- 

 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 de- 

 cays 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 

 sicklv 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 several organ- 

 isms which may possibly be causing 

 the disease have been isolated from 

 diseased tissue. Inoculations will be 

 made to determine which organism is 

 the cause. The life-history of the 

 pathogene will be studied and an at- 

 tempt made to work out some method 

 of control. This is necessarily 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) 

 Phyllosticta leafspot, affecting outdoor 



roses, chiefly ramblers; (3) other leaf 

 spots aad cane diseases of unknown 

 causes. Work upon the cause of the 

 diseases in this last group is now un- 

 der 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 prog- 

 ress will be made from time to time. 



Some misunderstanding seems to ex- 

 ist among growers in regard to send- 

 ing 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 in- 

 fonnation regarding the cause and con- 

 trol of the disease. Not only members 

 of the American Rose Society, but rose 

 growers in general may take advan- 

 tage of this opportunity to obtain in- 

 formation relating to rose troubles. 

 Hy sending specimens the grower wilt 

 not only help himself but will be ma- 

 terially aiding the project. Specimens 

 will always be appreciated, regardless 

 of whether or not they are of a new or 

 old disease, or of economic importance. 

 It is esjiecially desired at this time to- 

 obtain rose plants affected with root 

 diseases. 



Address all correspondence to L. 

 .\I. Massey, Department of Plant 

 Pathology, Cornell University, Ithaca, 

 N. Y. 



