The Rural Voice, 1982-08, Page 36FARM ADVICE
Fungus diseases increases in some shade species
Intensity and frequency of fungus
diseases infecting the foliage of certain
shade trees has increased significantly in
the past few years.
The relatively rare problems affecting
tree. appearance may now significantly
contribute to the decline and death of
whole trees. The susceptibility to these
diseases may,limit the use of certain trees
in garden landscapes.
One of the reasons for this disease
situation is a change in the climate, from
relatively predictable from about 1940 to
1970, to more erratic patterns with uneven
annual distribution of rainfall and unusual
temperatures - conditions conducive to
foliage disease development. The life
cycle of disease -causing fungi usually
begins with the overwintering of the
organisms within the dead infected tissue
(usually leaves) and late production of
spores which spread by the wind to the
new unfolding leaves.
If conditions permit, the spores
germinate on the leaf surface and the
fungi penetrate the leaf. As cells are
systematically infected. a visible brown
spot develops and grows and coalesces
with other expanding spots from other
infections. The leaf eventually withers and
falls from the twig.
Before reaching the stage of total leaf
collapse. more spores are produced within
the spots and are carried by wind or rain to
uninfected tissue. If conditions permit,
new infection centres develop. This may
continue throughout the season.
Some crabapples are highly susceptible
to Apple Scab fungus. This disease is well
known to apple growers because it affects
the fruit as well, and of the several sprays
applied before harvest, the majority
contain chemicals to control this fungus.
The effect on crabapples is gradual
defoliation, so that by mid-August there
are few leaves remaining and no re -
foliation takes place. Some crabapple
cultivars are quite resistant to Apple Scab.
These include "Dolgo", "Makamik",
"Red Jade", "Profusion", "White
Angel."
Hawthorns have been seriously affected
in the past few years by Hawthorn Leaf
Spot fungus. The effect on the plant is
similar to that of Apple Scab. Defoliation
begins in midsummer from the bottom,
leaving a few leaves at the top by
September. Pin -and red -flowering
hawthorns seem to be most susceptible.
Another common foliage disease is Leaf
Blotch of common Horse Chestnut and
Ohio Buckeye. Others of this species are
less susceptible. Like the previous pro-
blems. this disease infects as conditions
permit. "Blotching" of the leaves is
followed by their gradual deterioration
and leaf -fall through the summer as
infection spreads. Because the leaves are
larger. this disease is highly visible and
can be very unsightly.
One of the more spectacular foliage
111111...kg me
4,0
March 31, 1982 -10th Production Sale, Top Selling Bred York
Female 1.100 to Hugh Allin, Newcastle IAltario Farms 1
diseases is Sycamore Anthracnose, a
fungus disease affecting the Platanus
species, including London Plane and
American Sycamore. With the proper
conditions, especially temperature, this
fungus infects unfolding leaves and new
shoots causing them to wither quickly,
appearing as if damaged by late frost. This
infection may completely defoliate the
tree by the end of May. a few leaves at the
top usually escaping infection.
Under suitable conditions the fungus
may continue to spread into the bark of
twigs causing an annual canker and twig
girdling. Spores are produced in these
cankers as well as on overwintered fallen
leaves for reinfection that following
spring. Because defoliation occurs early in
the growing season, seriously defoliated
trees form new buds which break quickly,
and by mid-July affected trees appear
nomral except for the dead twigs girdled
by the disease.
Controlling leaf spots on a practical
scale seems at first glance, a relatively
simple procedure - simply spray the tree
with a suitable fungicide. For control
recommendations for foliage diseases see:
Insect and Disease Control in the Home
Garden, Ministry of Agriculture and Food
publication 64. This publication is avail-
able form local agricultural offices and the
Information Branch, Ontario Ministry of
Agriculture and Food, Legislative
Buildings, Toronto. Ontario M7A 1AS.
Peter F. Rice Royal Botanical Gardens
We offer you one of Ontario's largest selection of R.O.P. tested
and veterinary approved stock. Our herd is maintained as a closed
minimal disease operation.
Production Sale
Wed. Aug. 25 7 p.m.
90 open gilts, 70 boars, 10 bred gilts
A good selection of boars and gilts available
for sale at all times at the farm of Warren
Stein.
Located: 1 mile south and 2 miles
west of Tavistock
104
YORKSHIRE DUROC HAMPSHIRE LANDRACE E. HYBRIDS
R.R. 6, Woodstock, Ontario N4S 7W1
519-655-2942 or 462-2704
RICHARD AND WARREN STEIN
PG. 36 THE PUPAL VOICE/AUGUST 1982