Biology Reference
In-Depth Information
of very small, olive brown spores. The stem may
be girdled with dieback to that point.
Stem cankers are found around insect punc-
tures, thorn pricks, leaf or thorn scars, or abra-
sions caused by tying, but the majority of cankers
are formed at the cut end of a cane when a stub
has been left in pruning above a leaf axil or bud.
Roses cut properly close to a bud seldom develop
this canker. A rose stub usually dies back to the
first node, and since this fungus is a weak para-
site, it starts most readily in such dead or dying
tissue. When a cut is made close to the node, it is
quickly callused over, and the callus is a good
defense against wound fungi.
Control
Prune out cankered and dying stems as
soon as noticed. Make all cuts just above a bud or
leaf axil, not only at spring pruning but in cutting
flowers for the house or cutting off dead blooms
during the season.
Coniothyrium rosarum
Rose Graft Canker
.
This is a disease of roses under glass, starting at
the union of stock and scion in the warm moist
propagating frame and continuing in a large
amount of dead wood when plants are removed
to the greenhouse bench. Some consider the path-
ogen a form of
C. fuckelii
. Having measured
spores of the type specimen, in the Kew Herbar-
ium, I think they are distinct species, but that
some cases of graft canker are due to the common
canker fungus.
Coniothyrium wernsdorffiae
Rose Brand Can-
ker
, a rather rare but very serious disease. The
pathogen was named in Germany in 1905 and
was not reported in this country until 1925,
although it was subsequently shown to have
been collected in Canada in 1912 and in Pennsyl-
vania and Minnesota in 1914 and 1916. In 1926
a severe epiphytotic appeared at Ithaca, New
York, in the Cornell rose garden, infecting about
90 % of the climbers so seriously that the canes
had to be cut to the ground. Since then it has been
reported from a few other states, but in several
instances it has been confused with common
canker.
Small, dark reddish spots on canes enlarge and
acquire a more or less definite reddish brown or
purple margin, contrasting sharply with the green
of the cane. The center of the spot turns light
brown as the cells die, and little longitudinal
slits appear over the developing pycnidia. Spores
are olive brown, nearly twice the size of
C.
fuckelii
, and released through epidermal slits
instead of being spread in a sooty mass under
the epidermis. Cankers formed under the winter
protection of soil are black when roses are first
uncovered in spring, which explains the name
Brandfleckenkrankheit
,
meaning
fire-spot
disease.
C. wernsdorffiae
is a cold temperature fungus,
infecting rose canes under the winter covering,
entering through insect wounds, thorn scars,
scratches, and occasionally through dormant
buds. During a 4-year investigation at Ithaca,
I found no infection on canes not hilled with
earth or other moist cover over winter and no
natural infection during the summer.
Control
Omit the usual winter protection of soil
or other materials that keep canes moist. If brand
canker is a problem, just fasten canes of climbers
down near the ground, uncovered, and hope for
the best. Loss from winter injury will be less than
from the canker. Cut out diseased canes carefully.
Seiridium (Coryneum)
Blights
.
Coryneum
▶
Seiridium
cardinale
(
Leptosphaeria
sp., Telemorph)).
Coryneum Canker
of Cypress,
Bark Canker
of
cypress, incense ceder, common juniper and ori-
ental arborvitae.
Coryneum foliicola
Twig Canker
,
Fruit Rot
,
widespread on apple, affecting twigs, foliage
and fruit.
Seiridium cardinale (formerly
Coryneum
cardinale
(
Leptosphaeria
sp., Telemorph)).
Coryneum Canker
of Cypress,
Bark Canker
of
cypress, incense ceder, common juniper and ori-
ental arborvitae. This disease, since its discovery
in 1927, has been gradually exterminating Mon-
terey Cypress in most parts of California and is
cardinale (see
▶
