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Natur
Invasive Plant
e’
s
s own w
By Lisa Scott
eed whackers
I
w
t’
a
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y
t

ime to change the
plants by attacking the
plant tissue or root
b
reserves, yielding plants
with stunted growth
fr
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you think about
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best
and reduced
reproductive vigour.
F
vineyard or gard
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e
c
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ard,
I
In B.C.’s Southern
control is proving
nterior, biological
rom beetles to moths, insect
especially fruitful. Many
predators are being investigated
considered under control in localized
invasive species are now
aid in invasive plant control.
by Canada’s research scientists to
areas due to the establishment of
biological control agents. These species
LISA SCOTT
Mecinus janthinus weevil has
natural enemies for the suppression of
Biological control, or the use of
include diffuse knapweed, Dalmatian been deployed successfully
weed populations, was first introduced
toadflax, purple loosestrife and St.
against Dalmation toadflax.
to British Columbia in 1952 with the
John’s-wort, with others are expected in
release of the St. John’s-wort defoliating
the near future. In recent years, many
beetle
landowners have observed significant
weevil, typically 4-5 mm long. The
then, close to 60 agents have been
Chrysolina quadrigemina. Since
population reductions of diffuse
adults emerge in May and begin mating
established in B.C., providing control of
knapweed. There are, in fact, 12
after a short feeding period. Eggs are
approximately 20 different invasive
different species of insects and a fungus
laid into cavities chewed into the shoots.
plants. In fact, B.C. has the best track
that have been released in B.C. since
When larvae hatch, they mine the
record in Canada for running an
1972 in an effort to control diffuse
centre of the shoot and then pupate in
effective provincial biocontrol program.
knapweed.
the stem. Stems generally swell and
crack with the developing larvae inside,
numerous stages of approval are
Many years of research and
B.C. have seen a significant reduction in
Dalmatian toadflax populations in and the stem portion above the larvae
required for the development of a
recent years. This invasive plant with its
often dies. The new adults over winter
biological control agent before its
bright yellow snapdragon flowers was
in the stem and emerge in spring to
release. Most of the research takes place
once prolific along our roadsides and
start the whole process over again.
in Switzerland, as the majority of
grassland habitats. However, the release
invasive plants are of European origin.
of the weevil
make a comeback. This is due to a
Some years, the invaders appear to
the last decade has seriously thwarted
Mecinus janthinus during temporary reduction in the number of
hundreds of thousands of dollars.
Pre-release studies cost many
the spread of this weed.
insects. This is not totally unexpected,
However, this cost is justified by the
Mecinus is a black stem-boring
potential control benefits obtained —
specifically in terms of cost savings
through crop yield increases and
herbicide reductions, as well as the
NEED A BUILDING?
as the introduction of these insect
enemies essentially results in the
undetermined benefits to previously
displaced native plants and the wildlife
they support.
control agent, insects must be screened
Prior to establishing a biological
for host specificity to the target weed.
Seeds of native and agricultural plants
Woodworking shop,
in close association with the weed are
Okanagan Falls, BC
collected and shipped to Switzerland
where they are germinated and tested
MSC Metal Structure Concepts Inc. is a leader in the pre-engineered
Oyama, BC
Stag’s Hollow Winery,
Okanagan Falls, BC
Wild Goose Vineyards,
for damage from the potential agent.
steel building business. With 40 years’ experience selling and erecting
The agents are then tested to determine
pre-engineered steel buildings, MSC has the expertise to complete your
MSC Metal Structure Concepts Inc. is a leader in the pre-engineered
their impact to the host weed.
project in a cost-effective and timely manner.
steel building business. With 37 years’ experience selling and erecting
pre-engineered steel buildings, MSC has the expertise to complete your
Depending on biology, bioagents will
attack many different parts of a weed.
Some agents reduce seed production in
the larval stage by feeding on seed
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heads, as well as decreasing plant
strength by feeding on plant foliage as
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adults. Others directly weaken the
1-800-979-2993
www.mscsteel.com
FAX: 250-717-5751
British Columbia FRUIT GROWER • Winter 2009-10
19
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