Iowa County democrat. [volume] (Mineral Point, Wis.) 1877-1938, 1921-01-20
Horticultural
Hints
INJURY BY POWDERY MILDEW
ing to Control Disease Attacking
Various Trees.

Removal of widowed twigs in win
ter pruning to eliminate sources or
hOldover infection in dormant buds
and repeated spraying during the
growing season are the important steps
In proper control of apple powdery
mildew, according to specialists OF the
United States Department Of Agricui-
ture who have been Investigating this
menace to apples and other fruits in
the Pacific Northwest.
This disease has occasionally done
severe damage to Eastern orchards
also, and is recognized as a cause of
damage to nursery stock. While it at
tacks apple trees chiefly, it also occurs
on pear, ounce, plum, cherry and june
berry trees. Some varieties Of apples,
notably the White Pearmain and the
Winesap, are more resistant to this
malady than other varieties, though
none ere wholly immune.
The disease is caused by a fungus
that lives throughout the winter with
in the dormant buds and affects the
in the spring Where it is necessary
to spray for apple scab, and where
lime sulphur or other sprays are used
for this purpose, the treatment usually
suffices for mildew control. In regions
outside the range Of apple scab, espe-
cially in arid districts, mildeW must
be treated independently, the most eff
fective sprays being diluted lime-sul-
phur solutions and those containing
sulphur, finely divided.
The results of the investigations of
the United States Department Of Agri-
culture have been embodied in bull
letin, Control Of Apple PoWdery Mil
dew" which tells how to prepare and
apply the sprays. 1t also contains
spraying schedule showing cOnclSely
when and with what to spray. Copies
may be had by addressing the depart
ment at Washington.
The widowed shoots, which should
be pruned, are easily detected during
the dormant season by their gray or
silvery appearance. Isolated infection
existing in buds, however, makes it ln1-
possible to control the disease by prun'
ing alone In the spring and summer,
particularly the former, the fungus ap-
pears on the leaves, tender tWigs and
fruit, and sends down tiny suckers
that penetrate the cells of the growth
beneath These extract the sap of the
of 10
Since this mildew is largely foliage
disease and single infected leaf may
produce enough spores to infect many
trees it is important that every leaf
be covered by the spray. If the leaves
are thoroughly sprayed, twigs and fruit
will be covered at the same time. Lime
sulphur possesses the best wett1ng
power of any of the sprays ordinarily
used, but there is a tendency for it to
form in drops, leaving unprotected
areas The use of such "spreaders"
as caseine and saponin with any of the
sprays is advised.
The first application should be made
when the cluster buds have separated,
but before full bloom. 1t protects the
early foliage and blossoms and hard
ems tender varieties against subsequent
injuries from spraying.
The second application. or calyx
spray, should be applied as soon as
most of the petals have fallen. Lime
sulphur solution may be combined with
the arsenical solution used at this time
for codling-moth control. This spray
is very important and should not be
omitted.
A sulphur spray should be given
again about two weeks later. In the
hot interior districts of the Northwest
this constitutes the last time at which
sulphur materials may ordinarily be
used without danger of sulphur sun
burn"
The fourth application should follow
within two or three weeks, and at the
time of the second spraying for cod
ling-moth control. If mildew continues
to be very serious in the orchard, sui
phur materials must be used for eff
fective control. They are recommend
ed in any case if the fruit crop is light.
Otherwise, one of the copper sprays
may be used.
Later sprayings at intervals Of two
or three weeks until the latter part of
August is recommended where the dis
ease has become established.
air. o-1auunrnnv nj kNrc