The Bienville Democrat. [volume] (Arcadia, Bienville Parish, La.) 1912-1980, 1921-03-03
Horticultural
Hints
INJURY BY PoWDERY MILDEW
Specialists Advise Pruning and Spray.
ing to Control Disease Attacking
Various Trees.

ter pruning to eliminate sources OF
holdover infection in dormant buds,
and repeated spraying during the
growing season are the important steps
in proper control Of apple pow'lery
mildew, according to specialists of the
United States Department Of Agricul-
ture who have been Investigating this
menace to apples and other fruits 10
tho 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 1t 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
maIady than other varieties, though
none are wholly immune.
The disease Is caused by fungus
that lives throughout the winter With
in the dormant buds and affects the
new leaves, tender twigs and blossoms
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, e>pe-
cially in arid districts, mildew must
be treated independently, the most ef'
fective sprays being diluted lme'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 Mill
dew" which tells how to prepare and
apply the sprays. 1t also contains a
spraying schedule showing conclsely
when and with what to sIroy. Copies
may be had by addressing the depart
ment at Washington.
TIE mildewed shoots, which should
be pr,ned. are easily detected during
the dormant season by their gray or
silvery appearance. Isolated infection
existing in buds, however, makes II I'M
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
tree for the sustenance Of the fungus.
Since this mildew Is largely foliage
disease and single infected leaf may
produce enough spores to infect many
trees 1t is important that every leaf
be covered by the spray. If the leaves
are thoroughly sprayed, twlgs and fruit
will be covered at the same time. Lime
sulphur possesses the best wetting
power Of any of the sprays ordinarily
used, but there is tendency for IT 70
form In drops, leaving unprotected
areas. The use Of such "spreaders"
as caselne 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. Line
sulphur solution may be combined with
the arsenlcal solution used at this time
for codling.moth control. This spray
10 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 SUM-
burn
The fourth application should follow
within two or three weeks, and at the
time Of the second spraying for COD
ling.moth control. II mildew continues
to be very serious in the orchard, SUI
blur materials must be used tor e.
fective control. They are recommend
ed IL any case II the fruit crop Is light. |
Otherwise, one Of the copper sprays
may be used.