Lincoln County leader. [volume] (Toledo, Lincoln County, Or.) 1893-1987, 1911-03-31
PEACH LEAF CURL.
Comprehensive Directions for Its
Recognition and Treatment.

anist and plant pathologist, at the
Oregon Agricultural Experiment sta
tion, in a 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 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 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
r 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 lay
er on the surface of affected leaves.
These form under the cuticle, finally
pushing it off and imparting to the
surface frosted appearance. In each
sac are borne at first eight spores.
These become greatly increased in
numbers by budding within the sac.
The spores thus formed escape by the
rupture of the sac. These spores are
presumably 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 OF
less complete defoliation of the tree.
Such trees set little or no fruit. De.
foliated trees usually leaf out again SC
a 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 un-
. profitable.
Besides the method mentioned
above the fungus may be carried over
10 fha Ixv 1,
mycelium living over the winter ir
the twigs. The fungus gains entrance
to the twigs by the growth of the my.
celium down the leaf stalks of affect.
ed leaves into the twig. Where such
twigs remain alive over the winter
the leaves produced from the buds or
these twigs will always be infected
Fortunately only few branches be-
come infested in this way and the ma.
jority of these die before the next
spring, leaving only very small per.
centage of the infection, even in ser.
ious cases, caused by this method.
Control. Since the great majority
: of infections take place at the time
the buds open in the spring from
II spores adhering over winter to the
n buds, bud scales and twigs, it is OBJ
% vious that sray applied early in the
8. spring before the buds open, will kill
k the spores or prevent their germina
- tion and will control the disease.
"Use the bordeaux mixture $3.50
or the lime-sulphur 80 degrees baume
diluted 1-15 and apply early in the
. spring just before or while the buds
y are swelling, but before any of the
y buds show any green leaf tips. If any
y of the buds show the green tips of the
- leaves these may become infected
]. spraying will not prevent infec
y tion resulting from the mycelium win
" torinn quar- in tho hark of tho t,ui nru