356 
THE NATIONAL NURSERYMAN 
Roses and How to Grow Them 
The rose gardener should understand that roses are 
subject to a number of fungous growths causing serious 
diseases and that he must ward these off carefully if he 
would keep his plants in the healthful condition neces¬ 
sary for satisfactory growth and the production of blos¬ 
soms. These fungous parasites rarely kill the plants out¬ 
right, say specialists of the U. S. Department of Agri¬ 
culture, but by their presence the vigor of plants is great¬ 
ly reduced, the foliage may be rendered unsightly, 
branches more or less distorted or disfigured, and the 
quality of the blossoms lowered. In considering the fun¬ 
gous diseases of these plants the fact must be recognized 
that in common with similar diseases of other plants 
treatments are preventative rather than curative. While 
thorough and repeated sprayings wth 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 fungi¬ 
cidal applications can only be secured by their early use 
in the spring, guarding in this way against the recur¬ 
rence of a disease of the previous season. 
Fungicides to be recommended for rose diseases are 
Bordeaux mixture, lime-sulphur, potassium sulphid, and 
ammoniacal solution of copper carbonate. The lime-sul¬ 
phur has proved very valuable, especially in controlling 
mildew, as it does not injure the foliage of even delicate 
tea roses. 
Powdery Mildew.— Powdery mildew is extremely 
common, few gardens being entirely free from this most 
destructive of all rose diseases. Wild as well as culti¬ 
vated roses suffer from it, crimson ramblers being es¬ 
pecially susceptible. The fugus frequently appears very 
early in the season on young buds, leaves, and young 
shoots causing the appearance of a delicate white mil¬ 
dew that becomes mealy after the development of the 
summer spores. If the attack is severe, the normal de¬ 
velopment of the succulent young shoots is arrested, the 
leaves become curled and deformed, falling prematurely, 
and complete defoliation sometimes results. Later in the 
season the winter spores develop. These spores are ca¬ 
pable of persisting through the winter and setting up a 
new infection in the spring. 
Rose Rusts. —Rose rust appears as conspicuous, or- 
ange-clolored swellings on the green parts of rose bushes 
in the spring or early summer. Later these take a deep¬ 
er shade and become powdery. Small circular spots may 
occur on the leaves. 
Anthracnose.— Anthracnose attacks principally the 
leaves, but also, to some extent, the branches, causing 
the appearance of blotches, which later discharge a pink¬ 
ish mass of spores. The affected leaves are dwarfed and- 
fall. 
Leaf-spot.— There are several leaf-spot diseases of 
roses. In most cases the spots have a more or less 
brownish center with a purplish border. 
Leaf-blotch.— Leaf-blotch, which is also known as 
black-spot, ranks next to powdery mildew in frequency 
of occurrence. Bush roses are more susceptible to this 
trouble than climbing roses and the attacks are most se¬ 
vere in wet seasons. The first symptoms of the presence 
of the parasite are irregularly shaped, blackish spots 
without definite borders on the upper surface of mature 
or nearly full grown leaves. These spots may grow to¬ 
gether so as to cover almost the entire leaf. 
Practically all these diseases require the same treat¬ 
ment, which consists, in general, of careful spraying for 
control durng the growing season and the cutting out of 
diseased portions of the plant in the fall, folowed by 
more spraying of the shortened plant. The diseased 
wood removed, together with the old leaves and debris 
under bushes, should be burned. In case of attacks by 
rusts and leaf spots, the diseased wood or leaves should 
be removed and burned even during the growing season. 
For powdery mildew, the control sprayings should be 
with lime-sulphur or potassium sulphid. After cutting- 
back in the fall, a similar spray should be made use of. 
The control spraying for rusts should be ammoniacal 
copper carbonate. The fall spraying should be with a 
strong Bordeaux mixture. For leaf-spot and leaf-blight, 
the control sprays may be either Bordeaux mixture or 
ammoniacal copper carbonate, and the fall spraying 
should be with the former. 
Another disease to which roses are subject is canker. 
A wholly satisfactory method of control has not been 
worked out for this disease. The early symptoms are 
the appearance of small reddish patches on the green 
parts, generally of 1-year-old growth. The disease is 
caused by a fungus classed as a wound parasite, that is, 
the spores gain entrance to the bush through certain me¬ 
chanical injuries. These may be slight ones made upon 
the young branches by the thorns of the bush itself when 
one branch has been blown against another, or by insect 
punctures. Such infected areas may increase until the 
entire stem is surrounded and may extend for several 
inches along the branch. The only advice to be given is 
to cut away rigorously all diseased branches, and it may 
be necessary to cut back entire bushes if badly infected. 
Cover the exposed surfaces made by this cutting with 
paint or tar. This diseased material must be burned and 
the dormant bushes sprayed wth strong Bordeaux mix¬ 
ture in both the autumn and early spring. At the first 
appearance of the disease, cut away and destroy all 
branches showing infection. Then spray about every 10 
days, first with Bordeaux mixture and later wth ammo¬ 
niacal copper carbonate, as spraying has no disfiguring 
affect upon the foliage, an appearance to be avoided when 
blossoming time is near. It is possible that by such care¬ 
ful attention the bushes may outgrow the disease. 
W. 
Jonkoping, Sweden, July 29, 1916. 
Enclosed $2.00 as payment for your interesting and 
even instructive paper. One and one-third years, July 
1916-1917. 
Yours truly, 
M. P. Anderson. 
