Heppner gazette. [volume] (Heppner, Morrow County, Or.) 1892-1912, 1911-03-09
PEACH LEAF CURL.
Comprehensive Directions for Its
Recognition and Treatment.

! anist and plant pathologist, at tn
! Oregon Agricultural Experiment sta
/ tion, in a paper recently prepared
discussed at some length the natur,
and cure of what he considers to b.
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.o 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 characteristically curled.
This curling results from a 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 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 sc. 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 tis-
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 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 or
less complete defoliation of the tree
Such trees set little or no fruit. De-
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 un-
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
o the twigs by the growth of the my
.elium down the leaf stalks of affect
q 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.
only few branches be-
ONE infested in this way and the ma
ority of these die before the next
pring, leaving only very small per-
entage of the infection, even in SER ,
Gus cases, caused by this method.
Control. Since the great majority
f infections take place at the time
he buds open in the spring from
pores adhering over winter to the ,
uds, 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
r the lime-sulphur 80 degrees baume ,
iluted lis and apply early in the
Dring just before or while the buds
re swelling, but before any of the y
uds show any green leaf tips. If any 7
{ the buds show the green tips of the I.
aves these may become infected. =
Spraying will not prevent infec- :,
on resulting from the mycelium win :
ring over in the bark of the twigs. :
ortunately this method of wintsring ?
yer accounts for only small pro- y
)rtion of the infection. :,
"In spraying for leaf curl it is i'm =, -
,rtant that every twig be thoroughly =
'vered with the spray. =
Either of the sprays mentioned are
Iually good in preventing this dis
lse. The lime-sulphur, however, has
e advantage of being an insecticide :.
I'd will control the scale and is to be :
commended over the bordeaux mix :,
re on that account. " -