2015 clethodim vs butroxydim webinar-small

1. Life Impact The University of Adelaide
When is it worth rotating from
clethodim (eg. Select®) to butroxydim
(Factor®)?
Peter Boutsalis
University of Adelaide & Plant Science Consulting
Plant Science
Consulting

2. 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
Slide 2

3. 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

4. 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

5. 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
H2
H1
Target
enzyme
Target
enzyme
Target
enzyme
H2
H1
H2 H1

6. 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 profiles
At some sites, there a several mutations possible which often have different
resistance profiles
Mutations conferring resistance to FOPs more common that DIM mutations

7. Life Impact The University of Adelaide
Mutations causing Group A resistance

8. Group A DIM-resistance
Symptoms range from dead – stunted – healthy plants

9. Distribution of Group A herbicide
resistance in a paddock.
Why higher rates of clethodim/
butroxydim can control Group A
resistant ryegrass

10. 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

11. Random weed surveys between 2003-2013
• Points refer to paddocks sampled

12. Life Impact The University of Adelaide
Example of Random weed survey

13. Life Impact The University of Adelaide
Changes in Group A resistance
between 1998 & 2008 in the mid-
North, SA
Year
Target
site
resistant
Non-
target site
resistant
Hoegrass
1000ml/ha
Achieve
380g/ha
Axial
300ml/ha
Select
250ml/ha
2008 89 11 76 64 59 40
2003 83 17 77 45 36 31
1998 76 24 38 nt nt 19
Data 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

14. 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

15. 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

16. 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

17. Order of use of Group A herbicides for
ryegrass
FOPs> Achieve ≥ Axial > Select* ≥ Factor*
*rate effect

18. 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
300
Select
500
Select
1000
954 75 83 80 100 100
956 66 74 50 80 90
969 19 82 27 70 88
834 91 100 95 100 100
866 93 99 83 100 100
932 95 98 67 96 93
748 78 100 75 100 100
752 74 98 80 100 100
755 64 100 33 98 100
541 7 85 50 100 100
737 22 88 63 91 100
1212.3 40 77 69 56 100
1234.1 60 100 25 78 80
1197.2 55 85 80 100 100
1209.3 76 100 83 98 100
1174.2 21 81 40 98 100
1293 9 17 13 43 67
L300 63 93 75 98 100
L739 10 21 33 32 80
AUS93 68 100 90 100 100
SLR4 100 100 100 100 100
Green= 90-100% control
Yellow= 41-89 %control
Red= 0-40% control

19. 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 90
Kendenup WA 100 85
Naracoorte SA 80 85
Donald VIC 95 80
Corowa NSW 100 80
Horsham VIC 85 80
Esperance WA 65 70
Berrigan NSW 95 70
Horsham VIC 80 70
Corowa NSW 75 65
Williams WA 60 65
Cobram VIC 55 65
Berrigan NSW 100 65
Donald VIC 85 60
Horsham VIC 55 60
Horsham VIC 65 60
Corowa NSW 100 45
Tintinara SA 65 45
Corowa NSW 50 40
Donald VIC 80 40
Narrogin WA 70 40
Cunderdin WA 60 40
Horsham VIC 40 40
Horsham VIC 60 40
WA 30 25
Donald VIC 55 10
Corowa NSW 5 0

20. 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.

21. Whole plant resistance test
Lab tests cannot provide the information in this photo

22. Select, Factor, Select + Factor
250 500 750 900 11000
Select
Factor 80 Select 500 +
Factor 80
Factor 180

24. 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

25. Results Ratings
RRR
RR
R

26. Testing methods
Quick-Test Seed Test
www.plantscienceconsulting.com.au

27. 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

28. Life Impact The University of Adelaide
Effect of cold period/ frost before and after
clethodim treatment on ryegrass
1 10
0
20
40
60
80
100
S No Frost
S Frost Pre
S Frost Post
Clethodim (g ha-1
)
Dryweight(%control)
2013
1 10 100
0
20
40
60
80
100 NF
FBS
FAS
Clethodim g ha-1
Survival(%)
2014
Clethodim g ha-1
Survival(%)
1 10 100
0
20
40
60
80
100
NF
FBS
FAS
2012
Frost or cold period before or after
spraying can reduce clethodim efficacy
• NF = no frost,
• FBS= frost before spray
• FAS= frost after spray

29. 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

30. Life Impact The University of Adelaide
Conclusion: Final Slide
• Resistance testing: know what you’re
dealing with
• Ongoing research: Clethodim +
butroxydim mixes as short-term solution
• Multi-pronged approach required for
sustainable control of DIM resistant
ryegrass.