By Bernie Reppel
Herbicide resistance is an increasing challenge across Australia’s
northern grain belt. It is not just resistance to the essential glyphosate,
but resistances to herbicide groups A, B and C have also either been identified
or are expected.
In central Queensland, summer weeds are mostly at risk, while a mix of
summer and winter weeds are the worry in southern Queensland and northern
NSW. Winter weeds are mostly at risk in central NSW.
Seven weeds are confirmed resistant in southern Queensland and seven
in northern and central NSW. Central Queensland has no confirmed resistance
but a number of weeds have been identified as having “moderate to
high risk” of developing resistance.
The only constant across the region is the rating of common sowthistle
and summer grasses as “at high risk” of developing resistance
to group M herbicides.
In all parts of the northern region, the risk of resistance developing
is greatest for the cropping systems using zero tillage and/or limited
rotation between summer and winter crops.
According to Queensland Department of Primary Industries Toowoomba specialist,
Dr Steve Walker, glyphosate resistance is the main concern. “Growers
and advisers know what they can do about resistances to the other groups,
but glyphosate underpins the continuing viability of conservation cropping
in the north. So our aim is to ensure the maximum effective life of important
“When growers have zero till systems with little rotation between
summer and winter crops and they use more and more glyphosate, they are
hitting the same weed spectrum all the time.”
Dr Walker leads the GRDC-supported project ‘risk assessment and
preventive IWM (integrated weed management) strategies for herbicide resistance
in the diverse farming systems in the northern region’.
The team has established 10 long-term, on-farm, field experiments across
the region to test strategies to prevent at-risk weeds developing herbicide
resistance under the main crop rotations.
“We are evaluating more cost-effective options for managing weeds
in the long term, with the focus on running down the seed bank so paddocks
face fewer weed problems in the future,” says Dr Walker.
Common weeds of the three cropping zones of thenorthern grainr
egion that have developed herbicide resistance (
), or are considered to have a moderate to high risk of developing resistance
( ) for the
four main mode of action groups.
For more information:
Dr Steve Walker, 07 4639 8888, Steve.R.Walker@dpi.qld.gov.au
GRDC RESEARCH CODE DAQ 527, program 3
North, South, West