Herbicide resistance in wild oats & barnyard grass & resistance testing

Dr Peter Boutsalis, Dr Jenna Malone,

Christopher Preston & Gurjeet Gill.

School of Agriculture, Food and Wine

University of Adelaide

Plant ScienceConsulting

Why does herbicide resistance occur?

Herbicides don’t cause resistance!!

Resistance is naturally present.

Herbicides select and enrich resistance

Ryegrass/ wild radish- obligate outcrossing so

combine weak resistance strong resistance

Wild oats/ barnyard grass mostly self pollinate.

Frequency of resistance

Group A: 1 in 500,000 naturally resistant

Group B: 1 in 20,000 naturally resistant (25X)

Group M: very rare but its here!

Frequency of Group A Resistant Individuals in a 100 ha Paddock

Plant Density

1 m-2

10 m-2

100 m-2

1000 m-2

Plants

1 million

10 million

100 million

1 billion

Resistant Individuals

2

20

200

2000

(assume a frequency of 1 R/ 500,000 plants)

So a paddock with a low density of survivors may not look threatening but if they are resistant resistant seedbank!!

If continuous use, how soon does resistance happen? - Rules of Thumb

Herbicide Group Years to resistance

B- Glean 4

A- Hoegrass 6-8

C- Simazine 10-15

D- Trifluralin 10-15

F- Brodal ~10

L- Sprayseed >12

M- Glyphosate ~15

Life Impact The University of Adelaide

Resistance in wild oats?

• 1000+ Group A resistant cases

• Group B’s- few confirmed

• Mataven (Group Z)

• What is the information from random• surveys?

GRDC sponsored survey GOA 2013 – Wild oats

Survey area: Coonamble to Narromine, Nyngen to

Coolah

40 wild oat samples

Trends- incidence of resistance:– Very low : Atlantis, Verdict, Select

– Low : Axial

– Medium : Mataven

– High: Topik

Wild oat herbicide resistance

How real is the threat ?

NGA survey Oct 2007

(Richard Daniel)

Acknowledgment: Bayer CropScience, Nufarm and Syngenta who all contributed to the cost of testing

How widely did we survey ?

• Involved 34 agronomists from Sthn Qld to the Liverpool Plains and west to Walgett and Mungindi

• 61 seed samples from ‘high risk’ situations (Paddocks with wild oat herbicide performance issues in 2007 or having previous concerns)

• 36 seed samples from ‘random level’ situations (Nearly all paddocks unsprayed for wild oats in 2007. Best estimate of ‘average resistance levels’)

• All samples tested by Peter Boutsalis (Plant Science Consulting) with a common range of 9 herbicides

When were herbicides applied ?

Products Herbicide group (sub group)

Application timing

TriflurX + Avadex Xtra

D + E Pre-emergent, directly on seed then covered with 1 cm soil, to simulate IBS

Wildcat, Topik and Verdict

A (fop)

3 leaf stageAxial A (den)

Select A (dim)

Atlantis B

Mataven Z Jointing to first node, to simulate SST

Incidence(% of samples with ANY resistance)

0

20

40

60

80

100

Wildcat 300

mL/ha

Topik65

mL/ha

Verdict50

mL/ha

Axial150

mL/ha

Mataven1875

mL/ha

Atlantis 330

mL/ha

Select 175

mL/ha

TriflurX+

AvadexXtra

% o

f sa

mp

les

wit

h A

NY

re

sist

an

ce

High risk (61 samples) Random level (36 samples)

Were samples resistant to more than one herbicide ?

Frequency of multiple herbicide resistance

59% of ‘high risk’ samples had resistance to 3 or more different herbicides

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8

Resistance to number of herbicides

% o

f s

am

ple

s

High risk (61 samples) Random level (36 samples)

15% of ‘high risk’ samples were NOT resistant to any herbicide

78% of ‘random level’ samples were NOT resistant to any herbicide

Conclusions

1. Herbicide resistant wild oats are a real and escalating issue in the north.

2. Testing of ‘escapes’ in individual paddocks MUST become a key management practice. Test to see what will WORK

3. No single product/ strategy will provide the solution

Life Impact The University of Adelaide

Understanding Group A herbicide resistance

Peter Boutsalis, Jenna Malone, Christopher Preston, Sam Kleemann, Gurjeet Gill

School of Agriculture, Food & Wine, University of Adelaide,

Wild Oats resistance- Group A’sFOPS DEN DIM

If resistant to below: Topik Verdict Targa Axial Achieve Select Factor

Topik - ? ? ? ? ? ?

Verdict R - R ? ? ? ?

Targa R ? - ? ? ? ?

Axial R ? ? - R ? ?

Achieve R ? ? R ? - ? ?

Select R ? ? ? ? - ?

Factor R ? ? ? ? R? -

Rate response: 150ml/ha Axial vs 300ml/ha Axial

Photos

Axial regrowth

300 vs 150ml Axial

Avadex

Wild oats resistance- Group B’sSulfonylureas IMI’s TP’s

If resistant to below:

Hussar (ryegrass)

Atlantis (wild oats)

Intervix/ OnDuty Crusader

Hussar - R? ? R?

Atlantis R - ? R?

Intervix (Clearfield) R R - R

Crusader R R ? -

Mechanisms of resistance

Mechanisms of resistance

How are resistant plants different to susceptible plants?

1. Metabolic resistance

2. Target site resistance

3. Uptake & translocation

4. Sequestration

5. Increased expression of target site - eg.

glyphosate resistance in brome

Metabolic resistance

Plant enzymes detoxify the herbicides before they reach the target site

The herbicide will kill the plant if it reaches the target site in sufficient concentration

Occurs in wild oats, ryegrass

Location of sensitive target site. Plant is resistant

X

Herbicide

Target Site Resistance

• Some herbicides bind to single but different enzyme: – Group A (ACCase), – B (ALS), – C (PS2) ,– M (EPSPS)

• Variations in efficacy within a Group can

occur eg. between Topik, Verdict, Axial,

Achieve, Select.

Target Site Resistance

• Herbicides are chemically different and bind to

the target-site enzyme slightly differently

• Different mutations change the shape of the

target site affecting cross-resistance

H2H1

Target

enzyme

Target

enzyme

Target

enzyme

H2H1

H2 H1

Group A target site- ACCase gene

Group A biniding site

Group A resistance mutations

1781 1999 2027 2041 2078 2088 2096

Biotin carboxylase Biotin carrier Carboxyltransferase

ACCase gene

Distribution & understanting of Group A resistance using 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 Paddock 2 Paddock 3

ACCase Target site mutations

Life Impact The University of Adelaide

Glyphosate Resistance

Christopher Preston, Jenna Malone and Peter Boutsalis

School of Agriculture, Food & Wine, University of Adelaide

Life Impact The University of Adelaide

What we have so far

Annual ryegrass Barnyard grass Liverseed grass

Fleabane Windmill grass Great brome

Life Impact The University of Adelaide

Glyphosate resistance in awnless BYG

• 70 populations confirmed glyphosate resistant

• Lots more unconfirmed

• Cross-pollination low: 1.4%

• Mechanisms of resistance

• 1 = Target site resistant

• 10 = ‘other’ mechanism

• Temperature effects

Glyphosate resistant barnyard grass

Life Impact The University of Adelaide

Temperature and glyphosate resistance

• In some glyphosate resistant biotypes temperature affects efficacy.

• Related with the resistance mechanism

20oC 30oC

Resistance Testing

Would you pay $300 to ensure you don’t choose the

wrong herbicide??

Buy effective herbicides (save money)

Reduce crop competition yield

Reduce weed infestations restrict crop rotation

choice

Avoid increase resistant seedbanks

“Know your enemy”Testing for Herbicide Resistance

What tests are there?

1. During the growing season• Syngenta Herbicide Resistance Quick-Test• Test for resistance on surviving weeds• Grasses mainly• 4-5 weeks

2. At end of season (pre-harvest)• Seed testing• 8-10 weeks• Dormancy breaking easy (wild radish, wild oats, ryegrass etc.)• Seedlings transplanted

3. Crop Seed Quality Testing•Germination, Vigor, TSW, •Clearfield testing- wheat/ barley/ canola

PLANT SCIENCE CONSULTING

www.plantscienceconsulting.com

Quick-Test: Monitoring: identify survivors

Why has this individual survived and the others haven't?

Is it resistant?

Post Plants

Growth stage = 1-2 leaf to advanced tillering

Best stage is early tillering

Rinse soil off roots

Plants can be trimmed

Leaves dry

Add NO water

Quick-Test: collect plants

Make cuttings

Cuttings and re-growth

1. Cuttings2. Regrowth 5-10 days later3. Spray

Compared to Standard Resistant and Susceptible biotypes in every test

Assess 2-3 weeks after spray

Test for any post emergence herbicide

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 RRR

Select + 1% Hasten 200 A-DIM 20 R

Hussar + 1% Hasten 200 B-SU 90 RRR

Atrazine + 0.2% BS1000 2000 C 0 S

Triflur X 1000 D 0 S

Results Ratings

RRRRR

R

For more information

www.plantscienceconsulting.com.au