Saskatoon, Saskatchewan, Canada
January 3, 2008
Producers will need to take some
special steps to maintain the wheat midge tolerance in new wheat
varieties – varieties that were developed with producer funding
through the Western Grains Research
Foundation.
Seed from the new varieties will continue to be increased in
2008. Some limited quantities may be commercially available in
2009. The new varieties should result in large savings across a
broad region of the Prairies where the orange blossom wheat
midge often causes substantial losses.
Producers currently try to control wheat midge fly with
insecticides, but it’s difficult to assess which fields need
spraying and the window for effective application is short.
Insecticides also destroy beneficial parasitoids of midge. With
the new wheat midge tolerant varieties, there should be a
significant drop in the use of costly insecticides
The tolerance originates from the Sm1 gene that came from old
American soft red winter wheat varieties. It took more than 15
years for researchers at Agriculture and Agri-Food Canada in
Swift Current and Winnipeg to move the trait into spring wheat
varieties that also boast superior yield and agronomic traits.
“The wheat midge tolerance is produced by the early induction of
two naturally occurring compounds within the wheat kernels,”
explains Ron DePauw, a long-time wheat breeder with Agriculture
and Agri-Food Canada at Swift Current. “Due to these compounds,
wheat midge larvae are not able to develop when feeding on
immature kernels. These compounds dissipate by the time the crop
has matured.”
This is the only known gene that confers tolerance to wheat
midge. Unfortunately, tolerance based on a single gene has a
history of breaking down. That’s why producers will be asked to
take special measures when using the new varieties.
An interspersed refuge system, using blends of a midge tolerant
variety with a susceptible variety will be used to prolong the
life of the tolerance.
If a midge tolerant variety were grown as a pure stand, the only
midge surviving in the field would carry a mutation that allows
survival despite the presence of the Sm 1 gene. The virulent
midge would mate with other virulent midge and quickly build up
a large virulent population.
The interspersed refuge will involve blending 90 per cent of a
midge tolerant variety with 10 per cent of a susceptible
variety. Non-virulent midge will survive on the 10 per cent
susceptible plants and inter-mate with any virulent midge. The
progeny of this cross will be non-virulent.
“This could extend the effective life of midge tolerance from as
little as 10 years to 90 years or longer,” notes DePauw.
Over a period of years, the 10 per cent susceptible portion of
the seed blend sold to producers is likely to decrease due to
wheat midge damage.
“Producers funded the research with their check-off dollars to
help develop these tolerant varieties,” explains Lanette
Kuchenski, executive director with the Western Grains Research
Foundation. “Now it will require the responsible actions of
producers to preserve the midge tolerance into the future.”
Producers will need to test their farm saved seed to make sure
the 10 per cent refuge is being maintained and/or they will need
to repurchase certified seed every two or three years. Specific
recommendations will be developed before the seed is released
commercially.
Three of the varieties registered in February of 2007 are Canada
Western Red Spring (CWRS) wheat. Two of these will be
distributed by SeCan and one will be distributed by FarmPure
Seeds. The other registered variety is Canada Western Extra
Strong (CWES) wheat and will be distributed by Faurschou Farms.
Estimates generated by Agriculture and Agri-Food Canada put the
western Canadian loss from wheat midge in 2006 at over $40
million. Roughly half that amount was from yield reduction with
the other half coming from the grade loss due to midge-damaged
kernels. |
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