The Watertown weekly leader. [volume] (Watertown, Jefferson County, Wis.) 1912-1917, 1916-11-22

tBy WARNER J. MORSE, Phi. D., Path
ologist. Maine Agricultural Experiment
StatiOn)
In the summer of 1915 two foliage
troubles of the apple were observed,
of which there appears to have been no
previous record in this state. One of
these, which the writer has called
chlorosis, was widespread and COM
mon in a single orchard and occurred
to a certain extent on individual, scat
tered trees in the same locality. No
definite cause could be assigned to the
condition. The other, a disease previ
ouSly reported in Europe, Canada,
South Africa and New Zealand, is
known as silver-leaf and was found to
be fairly common in various parts of
the orchard-growing section of the
state.
ChIorosis.
In September, 1914, some diseased
apple leaves were received through the
college of agriculture from their exten-
sion representative in Franklin county,
Mr.. w. M. Morse. At that time the
trouble was known to exist on q single
tree, growing by the roadside in Liver
more Falls. Further observations by
Mr.. Morse in the spring and early sum-
mer of 1915 showed that this condition
of apple foliage had a wider distribu-
ton than was first Indicated, and led
to a visit to the locality by the writer
under his guidance.
AS far as observed this chlOrotic eff
feet on the leaves was limited to apple
trees in a rather restricted area of ad-
joining portions of the towns of Jay
and Livermore. Although several
less isolated affected trees, including
Baldwin, Northern Spy and Harvey va
rieties, were seen which were growing
on high, well-drained land under good
conditions, observations in Jay were
confined principally to single orchard
of Baldwins Of two or three acres in
extent. This orchard was on rather
low land, naturally moist, but was
fairly well drained with open bitches.
The leaf trouble was restricted to no
particular part of the orchard but was
apparently not quite so severe on the
higher portion. However, the trees
here were somewhat younger than the
rest. The majority of those affected
were probably twenty-five to thirty
years old and may have been older.
While they had apparently been neg
lected up to a few years ago their
treatment in this respect did not diff
fer from that given to the trees in
many other orchards in which no such
trouble occurred. For the past few
years they have been cultivated, ferti-
liked and pruned.
The trouble appeared on the younger
as well as the older branches, and is
In no way connected with the normal
following and falling of the inner and
more shaded leaves which is of COM
mon occurrence. Neither is it associ-
ated with any form of spray, for it
occurs on sprayed and unsprayed trees
alike. However, leaves so affected are
easily and sometimes severely injured
by lime-sulphur, used at a dilution
which gave absolutely no injurious eff
fects on the healthy foliage Of the
same tree.
The leaves showing the chlorosis
here described are, as a rule, variously
spotted or notified with irregular
splashes of yellow, giving variegated
appearance. No opportunity was af-
fOrded to follow the course of the dis
ease through the season, but it is
thought that the yellowing is progress
sive, eventually involving a large part
if not the whole Of the leaf, for some
were collected which showed but little
of the original green remaining.
Figures / and 2 illustrate the ap-
pearance of the affected leaves much
better than any written description.