2015 clethodim vs butroxydim webinar-small

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


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


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


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


Mutations causing Group A resistance

Group A DIM-resistance

Symptoms range from dead – stunted – healthy plants

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

Random weed surveys between 2003-2013

• Points refer to paddocks sampled


Example of Random weed survey


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


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.

Whole plant resistance test

Lab tests cannot provide the information in this photo

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

Results Ratings

RRRRR

R

Testing methods

Quick-Test Seed Test

www.plantscienceconsulting.com.au


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


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


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


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.

2015 clethodim vs butroxydim webinar-small

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