Australia
May 6, 2009
Source:
GRDC's The Crop Doctor
Eight years of determined effort
at overcoming herbicide resistant ryegrass has paid off
spectacularly for a group of grain growers in WA’s northern
agricultural region, with a remarkable 98% reduction in ryegrass
across 31 focus paddocks in a ‘real life’ research project.
Combining Integrated Weed Management (IWM) and herbicides on
their paddocks saw ryegrass reduced from an average of 183
plants/m2 to 4/m2. In most cases this was achieved while
maintaining high areas of crop. In approximately half those
paddocks that number was down to zero.
The growers were part of a
Grains Research and Development Corporation (GRDC) funded
research project led by 2008 GRDC Western Region Seed of Light
winner, Peter Newman of the Department of Agriculture and Food
WA (DAFWA).
It aimed to improve communication of IWM practices between
growers and evaluate their effectiveness in ‘real life’
situations.
Mr Newman said the project clearly demonstrated that growers who
determinedly target the seed banks of resistant weeds win the
battle in most cases.
While accepting that managing resistant weeds will be an ongoing
challenge, he believes growers are generally positive they can
keep winning.
He identifies some common management themes, including heavy use
of trifluralin in pre-sowing of all crops, high cereal crop
seeding rates, weed seed management at harvest by windrow
burning or chaff cart, sacrificing crops/pastures in weed
blow-outs and dedicated crop hygiene.
According to Mr Newman, many growers had resistant weed
management at the top of their list of worries a decade ago.
Today, while still a challenge, it’s been replaced with more
pressing concerns.
He’s convinced the main priority for GRDC and DAFWA agricultural
extension efforts should be managing resistant weeds, rather
than preventing them.
While prevention remains important for rare gene resistances
such as glyphosate, many growers now face the reality of
managing weeds resistant to multiple herbicide groups. The key
here is satisfactorily managing the seed bank.
Recent dry years in the region have seen a decline in livestock
and continuous cropping, mostly wheat, become the norm.
Trifluralin use has increased, with many growers applying it to
paddocks every year.
This is not recommended due to the risk of trifluralin
resistance and growers are urged to take a more integrated
approach.
New herbicides for controlling ryegrass and wild radish, with
novel modes of action, are coming onto the market and they will
greatly benefit WA growers.
However, these new effective herbicides are more expensive, so
there are good financial incentives for growers to manage
resistant weeds through integrated weed management so they don’t
have to rely solely on costly new herbicides.
New herbicides, along with IWM, will form the main artillery in
the grower’s arsenal against this menace for some time to come. |
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The Crop Doctor is
GRDC Managing Director,
Peter Reading |
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