Why worry about your elm?
What is your elm tree worth?
What is Dutch Elm Disease?
Tree Care Made Easy - Watering, Fertilizing, Pruning
Pruners and other Resources
Why
worry about your elm?
Dutch Elm Disease can infect
all
types of elms in Saskatchewan. American, Siberian &
Manchurian
elms are all susceptible and must be treated equally. American elms are
the
most common shade tree found in the older neighbourhoods of
Saskatoon.
In fact, there are as many as 100,000 in the city. American elms
are
native to Saskatchewan and therefore ideally suited to our cold, harsh
climate.
They can live for 250 years or more in our urban setting, providing
beauty
and shade for generations to come.
American elms have a
characteristic
“umbrella” shape when seen in profile, growing to 23 metres (75 feet)
in
urban conditions. The canopy of mature trees will often
meet
across a street creating an attractive “tunnel” of branches
and
leaves. Its dark green leaves are oval in shape and asymmetrical
(having
halves that are not even in size and shape) at the base. The leaf edges
are
double-toothed.
Leaf of an
American
Elm
|
 Leaf of a Siberian Elm |
Siberian elms (often
called
Manchurian elms) are less graceful and majestic than the American
elm.
A hardy, weedy, and relatively short lived species, the Siberian elm
can
have a variety of forms depending on location and pruning – from a
shrubby
hedge to a single tree. Their leaves are similar to, but smaller
than,
those of the American elm. Siberian elms are fast growing, typically
reaching
heights of 12 m (40 ft). They are unpopular with gardeners as
they
produce an abundance of seed and their branches break easily.
They
are less likely to die from DED, but can be a source of infection.
What is
your
elm tree worth?
In terms of Real Estate it
is
estimated that a mature American elm is worth at least $3,600.
This
doesn’t even begin to take into account the many other benefits of
trees,
such as shade and wind protection, as well as the beauty and clean air
they
provide.
Properly planted trees can
cut
air-conditioning and heating bills by 10-15 percent. Studies have
shown
that a mature urban forest increases property values by 5-20 percent,
improves
residents’ health and well-being, and can even reduce crime
rates!
If you’re a nature lover, consider the habitat that trees provide for
songbirds
and other animals. There are a multitude of reasons to save
our
urban forest. It costs as much as $1000 to remove a tree and as
little
as $250 to prune it. Why not keep your tree healthy and alive for
you
and your grandchildren to enjoy – it makes good financial sense.
What is
Dutch
Elm Disease?
Dutch Elm Disease (DED) is a
fatal
fungal disease that can kill an American elm in as few as three
weeks.
It is spread by the native elm bark beetle that feeds and breeds in elm
trees.
Elm bark beetles are tiny, about the size of a pinhead, and can be
present
without you noticing them. The disease is spread as beetles that are
infested
with the sticky DED spores move from tree to tree. Control the
beetle
and you can control DED!
DED was first identified
in
the Netherlands and northern France in 1919. It was actually
brought
to Europe from the Dutch East Indies during the late 19th century.
The first infections in
North
America were observed in the United States in Ohio in 1930. In
Canada,
the disease was first reported in Quebec in 1944. Since
then
DED has spread to almost everywhere that elms grow.
The first reported case of
DED
in Saskatchewan occurred in Regina in 1981. While the situation
there
is under control for now due to a very effective DED program,
other
areas of the province have not been as lucky. Manitoba has had
DED
since 1975. The disease spread rapidly from there into eastern
Saskatchewan
in the 1990s. This spread has largely occurred along natural
corridors
of wild elms, such as the Souris River Valley.
Unfortunately, DED can
move
very quickly. All it takes is someone transporting infested elm
firewood
to a disease-free zone. This is likely what happened when DED was
discovered
in Davidson in 1999. DED is now within an hour’s drive of
Saskatoon!
DED is almost here and
everyone,
young and old, must be ready to lend a helping hand. Are you
ready
to join the fight to save our elms? With your help we can win the
battle
and we will have elms to enjoy for years to come!
Can you
recognize
DED?
DED causes elms to shut down
their
water-conducting vessels so one of the first signs of the disease will
be
a branch in the upper canopy of an elm with leaves that wilt, turn
brown
and shrivel in early summer. They often remain on the tree for
the
full season. If the disease strikes later in the summer, leaves
will
usually wilt, turn yellow and fall prematurely.
If you see an elm with the
symptoms
of DED call the City of Saskatoon at 975-3300. The Pest Control
Officer
will take samples of the suspicious branches and send them away for
testing.
If the sample is positive for DED, the tree will be removed and buried
in
a designated area of the landfill. The quicker this happens the
better!
You are
responsible!
Elms that are located
on
city property, e.g. on boulevards and in parks, are maintained by
city
employees. However, privately owned trees are the responsibility
of
the landowner. It is up to you to make sure your elms are
maintained
for environmental and legal reasons as you are liable for any injuries
or
damages caused by fallen branches or dead trees.
This is what you should
do:
- Don’t store or transport elm firewood as
elm
bark beetles will breed in it. It is illegal! One two foot
piece
of elm wood can hold 1,800 infested beetles. Elm firewood must be
taken
to the city landfill where it will be buried to make it inaccessible
for
breeding.
- Hire a professional to
prune
the dead or broken branches from your elm trees to get rid of elm bark
beetle
breeding sites. Do not prune during the
pruning
ban (April 1st – August 31st) when the smell from cut branches
can
attract elm bark beetles.
- Band your trees for canker worms
every fall when the cankerworm population is high. This will not prevent DED,
but will keep your trees healthier and less likely to contract the disease.
Also, make sure to renew the sticky layer in the Spring if needed and remember
to take down your bands by May 15th.
- Watch for the symptoms
of
DED and report any suspicious looking trees.
Tree
Care
Made Easy!
Many people carefully water,
fertilize
and cut their lawns, but never give a second thought to their
trees.
Proper tree care is not much different. Trees also need watering,
fertilizing
and a good pruning every now and then!
Watering:
Elms are fairly resistant to drought, however if you notice that leaves
are
starting to droop during periods of very hot or dry weather it may be
time
to get out the hose. Infrequent, thorough soakings are better
than
frequent minimal watering. In the early morning, water the entire area
beneath
the crown of the tree with a sprinkler until at least 3 cm (1 in.) of
water
has been applied. This can be measured by placing empty tuna cans
under
the sprinkler and watering until the cans are full. Repeat this
weekly
and your tree will start to perk up!
Fertilizing:
Mature elms will benefit from a fertilizer application every two or
three
years. Fertilizer can be applied on the surface of the soil or in
“feeding”
holes that are dug in the soil around the tree from the drip line
(where
the outer edge of the canopy drips onto the soil) and outward.
Fertilize
in early spring before growth begins. For well established trees that
are
10 cm (4 in.) in diameter or more, apply 1 kg (2.2 lb.) of fertilizer
per
3 cm (1 in.) of trunk diameter using a 20:20:20 mix. Evenly
distribute
the fertilizer from the drip-line and out. After surface
applications,
make sure to water well.
Pruning
Because most elms are very
large
and require specialized skills and equipment to reach the top branches,
it
is recommended that a professional tree pruner be hired to do the
work.
Someone with ISA (International Society of Arboriculture) certification
is
best. Do not hire someone who “tops” trees as this simply
encourages
weedy, weak growth that may actually require more frequent
pruning!
A listing of pruners with ISA certification is included on the last
page.
Elms should be pruned every 5 to 7 years and also as soon as possible
after
any damage has occurred from storms, high winds or accidents. All
dead
and dying limbs should be removed so that elm bark beetles do not use
this
wood as a breeding site. Do not prune between
April
1st and August 31st when the smell of freshly cut branches
will
attract elm bark beetles to your yard. Do not
keep
the wood – it is illegal! Take all elm wood directly
to
the city landfill where it will be buried to make it inaccessible to
breeding
beetles.
If you are pruning a
smaller
elm tree you may wish to consider the following pointers:
- Prune all dead or dying
branches on a regular basis to improve the tree’s health and to avoid
future
problems.
- Prune to maintain the
desired
shape or size of the tree.
- Prune crossing or
rubbing
branches to avoid further damage.
- Prune to increase or
reduce
density of the tree branches. Generally trees should be thinned
to
produce an open crown allowing light and air to penetrate to the
interior.
Whether you are pruning a
tree
yourself or having someone else do the work, make sure that all pruning
equipment
is disinfected prior to and after each cut. Spraying your tools
with
a 50:50 mixture of bleach and water or with methyl hydrate (gasline
antifreeze)
will prevent the spread of disease to healthy parts of the tree or to
other
trees. In our climate pruning cuts should not be painted or
treated
in any way. Proper pruning is more important than wound treatment
for
quick healing of cuts.
Pruners
and
other Resources
ISA (International Society
of Arboriculture) Certified Tree Pruners located in Saskatoon
Resource
People
Saskatchewan
Dutch Elm Disease Association 933-5546
City of Saskatoon
975-3300
SOS Elms Coalition
Saskatchewan Environment
933-6515
Coalition to Save the Elms
Elmcare Site
College
of Agriculture – University of Saskatchewan
