4. Herbicide Resistance Surveys
Sampling
– End of season
– Collect seed from paddocks
randomly over a wide
geographic area
– Frequency 5-10 km
Evaluation- Pot testing
– Pot testing in winter
Resistance levels change so
need to revisit (eg 5 yr interval)
5. Uni of Adelaide random weed surveys between 2004-2014
(paddock surveyed)
8. Ryegrass resistance in West-Victoria
Western Victoria
Results of weed survey of 125 paddocks chosen at random in 2005 & 2010 conducted by the University of
Adelaide. Paddocks were scored as resistant if the seeds collected exhibited >20% survival in a pot test
conducted the following winter. Thus samples that exhibited 1% to less than 20% survival were scored as non-
resistant.
Region Year Trifluralin Hoegrass Glean Intervix Achieve Axial Select
VICTORIA
Western 2005 5 35 57 - 28 29 13
Wimmera 2 60 60 - 55 55 26
Mallee 7 12 54 - 3 7 0
Western 2010 25 40 73 18 35 33 5
Wimmera 35 60 74 18 57 54 9
Mallee 13 13 72 19 11 10 0
11. Ryegrass resistance- Group A’s
FOPS DEN DIM
If resistant
to below:
Hoegrass Verdict Targa Axial Achieve Select Factor
Hoegrass - R R ? ? ?
?
Verdict R - R
? ? ? ?
Targa R R -
? ? ? ?
Axial R R R - R
? ?
Achieve R R R R -
? ?
Select R R R R R -
?
Factor R R R R R R -
Rate response: Select, Factor, Select + Factor
12. Ryegrass resistance- Group B’s
Sulfonylureas IMI’s TP’s
If resistant to
below:
Logran Glean
Hussar
(ryegrass)
Atlantis
(wild oats)
Intervix/
OnDuty
Crusader
Logran - R ? ? ? ?
Glean R - ? ? ? ?
Hussar R R - R ? R
Atlantis R R R - ? R
Intervix R R R ? R ? - R ?
Crusader R R R R ? -
14. Different resistance occurs in a single paddock:
Group A target site resistance
2078 25
2041 3
2078, 2041 11
2078, 2088 5
2041, 1781 1
1781, 2041,
2078
1
2041, 2078,
2088
1
Paddock 1
• GROUP B target site resistance same senario
Paddock 2 Paddock 3
ACCase Target
site mutations
16. Herbicide tactics at different stages to
control weeds
Knockdowns (don’t overuse Gly) vs RR-canola
Rotate between different modes of action
Trifluralin, Avadex, Boxer Gold, Sakura, Rustler (IBS)
In-crop (Group A & B’s) resistance.
Opportunities exist- use Herbicide Resistance
Testing vs overuse of Sakura/ Boxer Gold!
Seed-set: Crop topping- canola, pulses, wheat
17. Successful weed control =
integrated weed management
1. Effective herbicides (resistance testing)
• Knockdown
• Pre-emergence
• Post-emergence
• Seed-set stage
2. Non-herbicide strategies
“when on a good thing don’t stick to it!!
18. IWM Crop Competition tactics
• Crop competition- barley-oats-trit-wheat-durum
• Crop choice- cereals vs broadleaf crops
• Seeding rate/ Crop density
• Row Spacing
• Cultivar choice
• Optimum planting time
• Seeding depth
• Seed vigor (Quality testing)
• Fertilizer timing
• Pest and disease management
19. Seedbanks- the seed in your paddock
• Surviving weeds set seed
– Ryegrass: 80,000 seeds/m2 [3-4 years)]
– Wild radish- 30,000 seeds/m2 [3-4 years]
– Brome- 3,000 seeds/m2 [2-3 years]
– Sowthistle- 68,000 seeds/m2 [< 1 year]
• Low numbers of resistant weeds can set lots of seeds
• Seed longevity
– Differs between species
– Left on surface [see above] vs burial (tillage systems)
23. NEW HERBICIDES
Adelaide University is investigating:
New MoA herbicides selective in wheat & canola
New non-selective knockdown herbicide
24. Life Impact The University of Adelaide
Product F applied IBS
25. What are your herbicide options?
Resistance testing
www.plantscienceconsulting.com.au
PLANT SCIENCE CONSULTING
26. Results using Seed Testing
Herbicide
Product
Rate
Herbicide
Group
Farmer
paddock
(g or ml/ha)
Surviva
l
(%)
Rating
Verdict + 1% Hasten 85 A-FOP 70 RR
Select + 1% Hasten 250 A-DIM 20 R
Select + 1% Hasten 500 A-DIM 0 S
Hussar + 1% Hasten 200 B-SU 90 RRR
Atrazine + 0.2% BS1000 2000 C 0 S
Triflur X 1000 D 0 S
What’s the outcome if farmer had chosen Verdict?
29. Life Impact The University of Adelaide
Two main species
of Brome
• B. diandrus (Great Brome)
– medium rainfall
regions
– generally earlier
germination
• B. rigidus (Rigid Brome)
– lower rainfall regions
– late and staggered
germination
Herbicide resistance in Brome
30. Life Impact The University of Adelaide
Herbicide resistance- random surveys
Survey Year Verdict
(%)
Select
(%)
Atlantis
(%)
South Australia
Mallee 2007 0 0 33
Mid North 2008 2 0 3
Eyre Peninsula 2009 0 0 5
Victoria
Western 2010 6 7 37
Northern 2011 0 0 0
31. Life Impact The University of Adelaide
Why Brome is a problem?
• Widely distributed
• Distribution increasing in no-till cropping
• Wide germination window
• Limited herbicide choice in-crop
– Wheat: Group B herbicides
– Broadleaf crops: Group A herbicides
• Herbicide resistance is developing
• IWM crucial eg. hay etc to stop seed-set.
(herbicides alone not the solution)
32. Life Impact The University of Adelaide
Multiple germinations
• Knockdown, pre-emergent, post-emergent
(dead plants), second post-m required.
33. Life Impact The University of Adelaide
Group A Resistance- Verdict
34. Life Impact The University of Adelaide
Group B IMI Resistance
(1800ml/ha Intervix)
35. Life Impact The University of Adelaide
Glyphosate resistance-
Maitland SA & Ouyen Vic.
Increasing rate improves control
36. Brome resistance- Group A’s
FOPS DIM
If resistant to
below:
Verdict Targa Select Factor
Verdict - R R ? R ?
Targa R - R ? R ?
Select R ? R ? - R ?
Factor R ? R ? R -
Can get rate response improving control
37. Brome resistance- Group B’s
Sulfonylureas IMI’s TP’s
If resistant to
below:
Monza Atlantis
Intervix/
OnDuty
Crusader
Monza - R?
?
R?
Atlantis R - ? R?
Intervix R R - R
Crusader R R ? -
38. Life Impact The University of Adelaide
Weed Control- in crop
• Knock-down (non-selective)- delayed
emergence!
• Pre-emergent herbicide mixes
– Trifluralin, Metribuzin, Sakura etc.
• Post-emergent herbicides
– Group A: Targa, Verdict, Select- dicot crops
– Group B: Atlantis, Crusader, Monza- wheat
– Group B: Intervix, Midas- Clearfield w/b/c
• Limited choice of different MoA herbicides
• Increased reliance on herbicides -> resistance
39. Life Impact The University of Adelaide
Brome grass control at Pira, Vic 2013
Untreated control
Sakura + Avadex Xtra
Source: M Witney (DM)
40. Life Impact The University of Adelaide
Efficacy of pre-em herbicides and brome seed germination
Slide 40
Trif750
Trif1500
Trif3000
Bromus diandrus
T-0
T-3
T-5
T-7
T-10
T-12
T-14
a
60g/ha
Sakura
120g/ha
Sakura
240g/ha
Bromus diandrus
T-0
T-3
T-5
T-7
T-10
T-12
T-14
n
75g/ha
M
etribuzin
150g/ha
M
etribuzin
300g/ha
Bromus diandrus
T-0
T-3
T-5
T-7
T-10
T-12
T-14
Trif750
Trif1500
Trif3000
0
20
40
60
80
100
Herbicidedamage(%)
Bromus diandrus
T-0
T-3
T-5
T-7
T-10
T-12
T-14
Sakura
60g/ha
Sakura
120g/ha
Sakura
240g/ha
0
20
40
60
80
100
Herbicidedamage(%)
Bromus diandrus
T-0
T-3
T-5
T-7
T-10
T-12
T-14
M
etribuzin
75g/ha
M
etribuzin
150g/ha
M
etribuzin
300g/ha
0
20
40
60
80
100
Herbicidedamage(%)
Bromus diandrus
T-0
T-3
T-5
T-7
T-10
T-12
T-14
b
d
f
Trifluralin
Sakura
Metribuzin
42. Wild Radish-
Wild
Radish
Year Region Glean 2,4-D
2009 S-Vic 0/15 0/15
2011 Vic Northern 0/2 1/2
Directed resistance testing:
Group B/F/I resistant wild radish detected in SA and Vic
43. Wild Radish
Genetically diverse like ryegrass.
Cross pollinates so resistance genes are transferred (= ryegrass)
Seedbank life: (3-4yr surface 6-8+ yr buried) exposure to same MoA.
Not all seeds germinate in following year.
Stacking of resistance (multiple resistance) = ryegrass
Rotate MoA groups B, C, F, H, I, even if cheaper herbicides working
Use full rates!!
Spray early- younger resistant weeds can be killed
– Especially contact herbicides- bromoxynil, diflufenican, velocity
Multiple herbicide timings- control new flushes
44. Sowthistle (% resistant samples)
Sowthistle
Year Region Glean 2,4-D
2009 S-Vic 0 0
2010 Vic Western 90
2011 Vic Northern 92
2012 SA Mallee/SE 80
The next big weed resistance problem!!
Directed resistance testing:
Group I resistance se SA
Group M resistance in s-NSW
45. Indian Hedge Mustard
(% resistant samples)
Indian Hedge Mustard
Year Region Glean Eclipse 24D
2008 SA Mid north 54 - 45
2013 SA Mid north 25 13 0
2009 SA Eyre Peninsula 52 57 0
2010 Vic Western 35 28 0
46. Indian Hedge Mustard
Western Victoria- IHM = incidence in 15% of
paddocks
Reliance on Group B/I I resistance B/I resistance
SA - Group B and I resistance (stacked resistance)
Western Vic:
– 3 cases: resistance to Brodal (3 L/ha)
– 1 case Atrazine (3 kg/ha)
– Mostly self-pollinated (pollen transfer very rare)
48. Where & why has glyphosate resistant ryegrass evolved?
Situation Number of sites States
Broadacre
cropping
Chemical fallow 32 NSW
Winter grains
Summer grains
Irrigated crops
295
1
1
Vic, SA, WA, NSW
NSW
SA
Horticulture Tree crops 10 NSW, SA
Vine crops
Vegetables
25
2
SA, WA
Vic
Other Driveway 5 NSW, Vic, SA, WA
Fence line /Crop
margin
Around buildings
89
2
NSW, SA, Vic, WA
NSW
Irrigation channel
/Drain
14 NSW, SA, Vic
Airstrip 1 SA
Railway 2 WA, NSW
Roadside 95 SA, NSW, WA
Intensive use of glyphosate >15yr with little alternative weed control practices
49. Facts about glyphosate resistant weeds
• All growth stages are resistant- seedlings,
pollen etc.
• Younger growth stages can be more sensitive.
• Resistance transferred by pollen & seed
• Progeny from survivors can be more resistant
(accumulation of mechanisms)
50. Increasing the level of glyphosate resistance:
mechanisms are additiveSurvival(%)
TS
S
Translocation
Cross: Translocation + TS
51. Variation in Glyphosate resistance in
ryegrass- resistance testing of
individual farmer samples
52. Different resistance profiles! Data courtesy of P. Boutsalis, Plant Science Consulting
53. Improving glyphosate efficacy
– Avoid treating plants with the below conditions:
• stressed plants
• high temperatures
• Poor coverage
• Dust covering leaves
• Confirmed resistance- resistance test
• Treating older plants (if one of the above conditions exists)
– Higher rates may not be effective on resistant plants unless a
resistance test confirms this.
– Prevent glyphosate resistant individuals set seed to avoid
accumulation of resistance mechanisms.
– Rotate from glyphosate even if no resistance (paraquat products/
residuals eg. bromacil along fencelines/ non-cropped areas).
– Resistance testing: for glyphosate resistance (several rates) important.
Point out intensively cropped areas.
More than 1000 sites
These areas are where resistance is highest.
Surveys
If cultivate pre sowing weed seeds get distributed throught the germination profile
Some pre-emergent herbicides don’t work as well
Trifluralin is not very mobile so wont control seeds at depth.
Also, seeds germinating- may get poorer control with trifluralin.
If cultivate pre sowing weed seeds get distributed throught the germination profile
Some pre-emergent herbicides don’t work as well
Trifluralin is not very mobile so wont control seeds at depth.
Also, seeds germinating- may get poorer control with trifluralin.
Boxer Gold® only needs about 5–10 mm of rain to wash it in and activate it, too much rain after application can cause crop damage. wheat is more susceptible to damage than barley.”
Sakura®, about 10–15 mm to activate it in the soil. problems can arise if the soil is dry on the surface but there is moist underneath. A small amount of rain might fall that is sufficient to germinate the weeds but not enough to activate the herbicide
