Life Impact The University of Adelaide
When is it worth rotating from clethodim (eg. Select®) to butroxydim
(Factor®)?
Peter BoutsalisUniversity of Adelaide & Plant Science Consulting
Plant ScienceConsulting
Life Impact The University of Adelaide
Outline
• Introduction to Group A herbicides
• Mode of action & Target site resistance
• Distribution of TS resistance- paddock & regional distribution.
• Efficacy of butroxydim and clethodim
• Quantifying resistance
• Other factors affecting DIM efficacy
• IWM of DIM resistant ryegrass eg. in canola
• Clethodim/butroxydim should be used as part of an IWM strategy to control ryegrass
Slide 2
Life Impact The University of Adelaide
Classifying Group A’s
• According to chemical family: FOPs, DIMs, DEN
• Classifying Group A’s according to wheat selectivity.
• Wheat selective Group A’s
– Resistance can be due to metabolic or target site resistance
– Hoegrass, Topik, Achieve, Axial etc.
• Broadleaf crop selective Group A’s
– No metabolism of these herbicides in wheat
– Target site resistance
– Verdict, Targa, Select, Factor
Slide 3
Life Impact The University of Adelaide
How do DIMs work
• All Group A’s inhibit one enzyme
• Acetyl Coenzyme A Carboxylase (ACCase).
• All Group A’s bind to one site on ACCase
• Binding not identical
• Mutations at this binding site cause reduced binding therefore resistance
Target Site Resistance: Variations even occur within a Group-DIMs (between Achieve, Select, Factor)
• Herbicides are chemically different and bind to the target in slightly different ways.
• Different mutations change the target site in different ways
H2H1
Target
enzyme
Target
enzyme
Target
enzyme
H2H1
H2 H1
Group A resistance mutations
1781 1999 2027 2041 2078 2088 2096
Biotin carboxylase Biotin carrier Carboxyl transferase
ACCase gene
7 mutation sites have been identified.Different sites give rise to different resistance profilesAt some sites, there a several mutations possible which often have different resistance profilesMutations conferring resistance to FOPs more common that DIM mutations
Distribution of Group A herbicide resistance in a paddock.
Why higher rates of clethodim/ butroxydim can control Group A
resistant ryegrass
Distribution of resistance – DNA technology
2078 25
2041 3
2078, 2041 11
2078, 2088 5
2041, 1781 1
1781, 2041, 2078 1
2041, 2078, 2088 1
Paddock 1
Different mutations can occur in a single paddock!!!!Clethodim/ butroxydim unlikely to control plants with double/triple mutations
Paddock 2 Paddock 3
ACCase Target site mutations
Life Impact The University of Adelaide
Changes in Group A resistance between 1998 & 2008 in the mid-
North, SAData is % of resistant paddock samples in a pot test
Data is % of Hoegrass resistant samples with 1 or 2 ACCase target site mutations
Non-target site resistance: Metabolic, new mechanism or Target site not discovered yet
Mutation 1998 2003 2008 1781 6 8 13 2027 10 7 6 2041 40 32 43 2078 13 13 21 2088 11 6 19 2096 1 1
1781, 1999 1 1781, 2027 1 1781, 2041 3 2 14 1781, 2078 3 3 1781, 2096 2 1999, 2041 1 1999, 2078 3 2027, 2041 2 2 2027, 2078 3 2041, 2078 3 5 4 2041, 2088 1 3 2078, 2088 6 3 2078, 2096 2 2088, 2096 1
Distribution of ACCase mutations in SA
60-70% of R plants from all years had 1 mutation
6%of R plants had two mutations from 1998 survey
22-23% of R plants had two mutations in 2003 & 2008
Life Impact The University of Adelaide
Resistance to Clethodim & Butroxydim
• Research to date has shown that Clethodim
or Butroxydim resistance in ryegrass is due
to Group A TARGET SITE resistance.
• “But increasing the DIM rate often improves
control” Isn’t this classic ‘Metabolic
resistance’?? NO
• Few cases of ryegrass with Clethodim/
Butroxydim that don’t possess the common
TS resistance mutations
Factor vs Select on ryegrass
High rates of Select improve control
Factor can sometimes improve control on Select
resistant ryegrass (depends on mutations)
Sometimes Select better than Factor
Factor + Select mixtures- possible synergism.
Some mutations may have fitness penalty
Order of use of Group A herbicides for ryegrass
FOPs> Achieve ≥ Axial > Select* ≥ Factor**rate effect
Select vs Factor in controlling Group A resistant ryegrass- 1 trial
Data is Control (%) Growth stage at spraying was 3 leaf stage. Supercharge used with Factor, Hasten used with Select.
Biotype Factor 100
Factor 180 Select
300Select
500Select 1000
954 75 83 80 100 100956 66 74 50 80 90969 19 82 27 70 88834 91 100 95 100 100866 93 99 83 100 100932 95 98 67 96 93748 78 100 75 100 100752 74 98 80 100 100755 64 100 33 98 100541 7 85 50 100 100737 22 88 63 91 1001212.3 40 77 69 56 1001234.1 60 100 25 78 801197.2 55 85 80 100 1001209.3 76 100 83 98 1001174.2 21 81 40 98 1001293 9 17 13 43 67L300 63 93 75 98 100L739 10 21 33 32 80AUS93 68 100 90 100 100SLR4 100 100 100 100 100
Green= 90-100% control
Yellow= 41-89 %control
Red= 0-40% control
Select vs Factor in controlling Group A resistant ryegrass- PSC results
Data is Control (%)
Green= 90-100% control
Yellow= 41-89 %control
Red= 0-40% control
Town State Factor 180 Select 500 WA 90 90
Ardrossan SA 100 90Kendenup WA 100 85Naracoorte SA 80 85
Donald VIC 95 80Corowa NSW 100 80
Horsham VIC 85 80Esperance WA 65 70Berrigan NSW 95 70Horsham VIC 80 70Corowa NSW 75 65Williams WA 60 65Cobram VIC 55 65Berrigan NSW 100 65Donald VIC 85 60
Horsham VIC 55 60Horsham VIC 65 60Corowa NSW 100 45
Tintinara SA 65 45Corowa NSW 50 40Donald VIC 80 40
Narrogin WA 70 40Cunderdin WA 60 40Horsham VIC 40 40Horsham VIC 60 40
WA 30 25Donald VIC 55 10Corowa NSW 5 0
What mutations occur in my paddock?
Commercial DNA analysis not available commercially
DNA analysis mainly used to test for presence of
known mutations
Multiple mechanisms are responsible for resistance
What information do growers actually require?
Which herbicides work and at what rates!!
Currently only possible with a whole plant resistance
test.
Select, Factor, Select + Factor
250 500 750 900 11000
Select
Factor 80 Select 500 + Factor 80
Factor 180
Ryegrass resistance- Relationship between 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
Life Impact The University of Adelaide
Field failures are not always due to resistance. (verify with a test)
Getting the most out of DIM herbicides
• Spraying younger plants vs waiting to ‘get them all’
• By default, earlier spraying
• Younger weeds
• warmer conditions
• Less chance of frost
• Reduced control when ryegrass stressed
• Spray before frost vs after frost
Slide 28
Improved efficacy
Life Impact The University of Adelaide
Effect of cold period/ frost before and after clethodim treatment on ryegrass
1 100
20
40
60
80
100
S No FrostS Frost PreS Frost Post
Clethodim (g ha-1)
Dry
wei
gh
t (%
co
ntr
ol)
2012Frost or cold period before or after
spraying can reduce clethodim efficacy
• NF = no frost, • FBS= frost before spray• FAS= frost after spray
Life Impact The University of Adelaide
Managing clethodim resistant ryegrass in canola- IWM strategies.
• Reduce seedbank to take pressure of DIMs eg. knockdowns, pre-emergent & seed-set control
• Seed-set control- manage survivors/ late germinators.
• Target young weeds
• Warmer temp’s can increase DIM activity
• Frost after clethodim application reduces efficacy.
• Addition of low rate Factor (80g/ha) may improve clethodim activity
• Rotate- glyphosate, TT, CLR
• Alternative MOA herbicides
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