The Athena press. [volume] (Athena, Umatilla County, Or.) 18??-1942, 1911-04-21
PEACH LEAF CURL.
Comprehensive Directions for 1t:
Recognition and Treatment.

Oregon Agricultural Experiment sta
tion, in paper recently prepared,
discussed at some length the nature
and cure of what he considers to be
most common and destructive disease
of the peach which is met with in the
Northwest.
"The most common and destructive
disease of the peach in the humid sec
tions of the Northwest and probably
wherever the peach is grown in this
region is without doubt the peach leaf
curl or, as it is commonly known
among growers, the curl leaf.
"The disease may be recognized by
the characteristic effect upon the fol-
iage and twigs. The leaves are pecul-
iarly and Enthusiastically curled.
This curling results from stimula-
tion induced by a parasitic fungus
which grows among the cells of the
leaf. The infected leaves become
considerably increased in thickness
and breadth. The cells of the tissues
develop thickened walls and increase
in size and number. The tissues of
the midrib do not increase to any ex-
tent and the abnormal growth in the
tissues on either side as described
above, results in a puckering or curl
ing. Since the greatest growth is in
the tissues toward the upper side
there is tendency for the upper sur
face of the curled leaf to be convex.
Affected twigs are increased in thick
ness and very much shortened. The
green coloring matter normally pres
ent in healthy twigs is largely bleach
ed out so that diseased twigs appear
whitish.
"The parasitic fungus causing the
trouble is known as eXoascus defor-
mans. The vegetative condition of
the fungus, the mycelium, is present
among the cells of all diseased It's
sues, absorbing the juices needed for
the proper growth of the tree and
stimulating the tissues to produce the
abnormal structures described above
which are not able to properly per-
form the functions of normal tissues.
Productive bodies or spores are pro-
duced in little sacs which form a lay
er on the surface of affected leaves.
These form under the cuticle, finally
pushing it off and imparting to the
surface a frosted appearance. In each
sac are borne at first eight spores.
These become greatly increased in
by budding within the sac.
The spores thus formed escape by the
rupture of the sac. These spores are
carried over the winter on
the surface of twigs and bud scales
and produce infection as soon as the
leaf buds open in spring.
affected foliage usually drops and
where abundant may cause more or
less complete defoliation of the tree.
Such trees set little or no fruit. De-
foliated trees usually leaf out again so
that in midsummer no signs of the
disease may be found. The effect of
such defoliation however, is to stunt
the tree. Trees allowed to become in
fected year after year are usually I'M
profitable.
"Besides the method mentioned
above the fungus may be carried over
rom one season to the next by the
nycelium living over the winter in
he twigs. The fungus gains entrance
% the twigs by the growth of the my
,elium down the leaf stalks of affect
ID leaves into the twig. Where such
wigs remain alive over the winter
he leaves produced from the buds on
,hese twigs will always be infected. |
fortunately only few branches be-
,ome infested in this way and the ma
ority of these die before the next
spring, leaving only a very small per-
,entage of the infection, even in SER
Gus cases, caused by this method.
Control. Since the great majority
If infections take place at the time
he buds open in the spring from
spores adhering over winter to the
buds, bud scales and twigs, it is OBJ
'ious that sray applied early in the
pring before the buds open, will kill
he spores or prevent their germina-
ion and will control the disease.
"Use the bordeaux mixture $3.50 |
n the lime-sulphur 80 degrees baume
liluted LIS and apply early in the
pring just before or while the buds
ire swelling, but before any of the
'uds show any green leaf tips. If any
# the buds show the green tips of the
caves these may become infected.
Spraying will not prevent infec-
ion resulting from the mycelium win
ering over in the bark of the twigs.
fortunately this method of wintering
'ver accounts for only a small pro-
,ortion Of the infection.
In spraying for leaf curl it is i'm
oortant that every twig be thoroughly
overed with the spray.
Either of the sprays mentioned are
.qually good in preventing this dis
.ase. The lime-sulphur, however, has
he advantage of being an insecticide
md will control the scale and is to be