3. Resistance Surveys
Frequency of herbicide resistance
in Western Australia
Mechelle Owen, Michael Walsh & Stephen Powles
Australian Herbicide Resistance Initiative
www.ahri.uwa.edu.au
4. Crop variety testing zones
30 plus sites visited
in each region
Sampled
every 5km
H
7. Years to resistance for different herbicides - USA
35
ALS Inhibitors
30
25
Resistant species
20
ACCase inhibitors
15
Triazines
10
5
Glyphosate
0
0 10 20 30 40 50
Years of use
22. Corn, Cotton
and Soybean
Belt
Corn 40 m ha
Soybean 30 m ha
Cotton 5 m ha
23. Corn, Cotton
and Soybean
Belt
Corn 40 m ha (85% glyphosate resistant)
Soybean 30 m ha (95% glyphosate resistant)
Cotton 5 m ha (95% glyphosate resistant)
28. Learning from Canada
• Wheat the major crop
• GM Canola dominant but with diversity
- Liberty Link Canola
- Clearfield Canola
- RR Canola – 80%
Diversity in crops and herbicides=
Sustainability
29. Glyphosate Resistance in Australia
133 cases of resistant ryegrass
State No of populations
SA 49
NSW 48
WA 22
Vic 14
Other Species - Liverseed grass (3)
- Awnless barnyard grass (18)
- Windmill grass (1)
- Fleabane (8)
Photo: Andrew Heinrich
30. Glyphosate resistance
• Not limited to broadacre situations resistance has
been found in:
• Vineyards
• Orchards
• Roadside verges
• Railway lines
• Irrigation channels
• Airstrips
• Fencelines/crop margins – using glyphosate as
only method for weed control will lead to evolution
of resistance
GLYPHOSATE STILL WORKING ON
MOST FARMS – KEEP IT THAT WAY
Photo: Andrew Heinrich
31. Probability of glyphosate resistance
1
Glyphosate every year
Probability of resistance
0.8 Glyphosate/paraquat rotation
Glyphosate then paraquat sequence
0.6
0.4
0.2
0
0 5 10 15 20 25 30
Year
Neve et al 2003 weed research
Cumulative probability distributions for predicted evolution of glyphosate resistance in annual ryegrass
in a 30-year simulation of a Wheat-Lupin-Wheat-Canola rotation with no tillage at sowing
32.
33. Harvest weed seed
mgt, double knock!
• Up to 85% of ryegrass seed “harvested”
can be collected in the chaff fraction