Evening star., 1950-10-01

merits local gardeners attention.
nse OF an introduction, nor is 1t
'er, due to commercial practices 1t
is being spread, perhaps more
rapidly by man than 1t would be
by nature alone.
The disease has spread as far
north as Rockville, Md, from the
point Of it's earliest mention, the
State of Georgia. The spot
anthracnose of dogwood attacks
the flowers, leaves and woody
stems and is probably most objec-
tionable because of disfiguring the
flowers. Named in 1948 by the
Brazilian pathologist, DR.. A. A.
Bitancourt. who observed it while
visiting this country. it has since
been observed in many sections,
although systematic surveys have
only been started.
Too new to have been studied
for controls, still we do have the
advice of one grower near Snow
Hill, Md, who found that the
Bordeaux mixture and fermate
brought a considerable degree of
control. 1t is believed that
dormant application of lime e-sul-
phur followed by several applica-
tions of fermate will result in COM
plete control, but this theory Is
yet to be tested. Gardeners who
wish to start immediate control
might well follow these suggestions
until definite recommendations are
formulated.
Spots on the Flowers.
The disease is most readily rec
ognized by disflguring spots on
the flowers, or possibly by the
"shot-holes" left in the leaves.
The LESSONS on the twigs are so
small that one should have lens
to see them. However, the rough
ness of the bark to the touch may
tell If the twigs are infected If a
lens is lacking.
The disease has been spread in
part through the commercial
movement of dogwoods from the
propagators in the South to the
retailers in the north. Although,
there is some merit to the claim
that ordinary highway traffic has
had something to do with the
spread because most of the local
infections discovered were along
the highways. This may or may
not be true when systematic
studies are made of the dogwoods
on a more widespread scale. In
the meantime it is desirable to
watch for signs of the spot an
thracnose on local trees. Infected
flowers were found near La Plata,
Md, April, 1949, and photo
graphed by w. F. Jeffers, USDA.
While there are a number of
foliage diseases of the dogwood,
only the Spot Anthracnose pro-
duces the shot-hole effect. Un-
der lens, the spots of infection
show a distinct coloring at the
margins.
Borers Will Not Attack.
A second suggestion has been
made that we keep the dogwood
trees well mulched and avoid dis
turbing the soil over the shallow
growing roots. Perhaps a light |
of a commercial ferti-
lizer will increase the vigor and
possibly the resistance of the tree
to this and other diseases. Such |
attention cannot possibly be
wasted since it is a fact that the
fat-headed apple borer will not
attack a strongly growing dog
wood tree, but let the tree suffer
injury or be weakened by any
cause and the borer will imme-
diately start to work.
There seems to be some dis
agreement as to the susceptibility
of the pink dogwood to the spot
anthracnose. In Georgia they
claim that the pink dogwoods were
not affected, while in Maryland
they are reported to have been
infected. 1t would seem strange
if this were. true, but current sur
veys should provide the answer.
In the meantime gardeners might
well keep a careful check and re-
port the location of infected trees
and be prepared to protect their
trees.