Managing Herbicide Resistance

Franck E. Dayan

Bioagricultural Sciences and Pest Management

Colorado State University

• Evolution of herbicide resistance

• Different types of mechanisms of resistance

• Resistance to glyphosate, PPO inhibitors, ALS inhibitors and PGR

• Multiple herbicide resistance

• Managing herbicide resistance

Outline

Darwin focused on the change resulting from a Competitive Struggle for Existence

Mr. Herbert Spencer was influenced by Darwin’s The Origin of Species and coined the term ‘Survival of the Fittest’

Darwin later adopted the term to mean ‘better designed for an immediate, local environment’

Evolution

Individuals able to survive a herbicide dose that normally provides effective control of that species

Evolution of herbicide resistance

"better designed for an immediate, local environment“

Délye et al. 2013 DNA Analysis of herbarium specimens of the grass weed Alopecurus myosuroides reveals herbicide resistance pre-dated herbicides. PLoS ONE 8(10): e75117. doi:10.1371/journal.pone.0075117

Old herbarium collections

Between 1788 and 1975 • Before any ACCase (Group 1) herbicides

Mutation for resistance to both FOPs and DIMs found in a sample from 1888

Blackgrass from France

Resistance exists before any herbicides are used

Left to Right: • Rice • Barnyard grass Mimics rice • Barnyard grass Normal • Genetic trait

Resistance will evolve to any persistent selection pressure

Avoids hand weeding

Emergence to Flowering (days)

20 40 60 80

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Slide by M. Walsh Harrington Seed

Destructor

Resistance will evolve to any persistent selection pressure

Intercepts and destroys weed seeds during grain crop harvest. The interception and destruction of weed seeds occurs during grain crop harvest on the chaff fraction exiting the grain harvester

Adaptive capacity of wild radish to halve its time to flowering following five generations

Avoids seed destruction

Chronological increase in unique (species and

MOA) cases of evolved herbicide-resistant weeds worldwide

History of herbicide resistance

1st reports of ALS & ACCase resistance

- mid 80’s

RR™ introduced US in 1996

Roundup resistance

1st report of triazine resistance - 1968

Duke, S. O.; Dayan, F. E., Herbicides. In eLS, John Wiley & Sons, Ltd: Chichester, UK, 2018; p 11

Herbicide Resistance by MOA

History of herbicide resistance

Busi et al 2018 Weed resistance to synthetic auxin herbicides. Pest Manag. Sci. 2018, 74, 2265-2276

ALS inhibitors (1979)

Accase inhibitors (1974)

Glyphosate (1974)

Synthetic auxins (1945)

History of herbicide resistance

History of herbicide resistance

History of herbicide resistance

Weed biology

1. Outcrosser/self-infertility

2. High level of genetic diversity

3. High seed production

4. Some seed dormancy

5. Highly competitive

Characteristics associated with resistance

1. MOA involves a primary gene product 2. Nuclear-encoded, semi-dominant or

dominant gene 3. Herbicide is a non-competitive

inhibitor 4. No fitness penalty for resistance 5. Herbicide is extremely effective 6. Has some persistence in the soil

Characteristics associated with resistance

Herbicide chemistry

1. Frequent use of herbicides with a similar mechanism of action – this is the most important of all factors

2. Monocultures and crop rotations that rely on the same herbicide mechanism of action for weed control

3. Lack of non-chemical weed control practices such as cultivation, stubble burning, stale seedbeds and competitive and cover crops

Characteristics associated with resistance

Resistance linked to farming practices

Any trait which slows/prevents herbicide reaching the site of action, or reduces toxic effect at site of action

Target Site

Mutation Increased expression/ Gene amplification

Potential Herbicide Resistance Mechanisms

Non-Target Site

Metabolism Altered translocation & sequestration

Reduced foliar uptake

General oxidative stress response

Resistance mechanisms

Resistance to glyphosate

Glyphosate-resistant species Year Populations Situation

Annual ryegrass (Lolium rigidum) 1996 678# everywhere gly is used

Awnless Barnyard grass (Echinochloa colona) 2007 102 herbicide fallow

Liverseed grass (Urochloa panicoides) 2008 4 herbicide fallow

Flaxleaf fleabane (Conyza bonariensis) 2010 65 roadsides

Windmill grass (Chloris truncata) 2010 11 herbicide fallow; roadsides

Wild radish (Raphanus raphanistrum) 2010 3 herbicide fallow

Great brome (Bromus diandrus) 2011 5 fence lines

Tall fleabane (Conyza sumatrensis) 2012 8 roadsides

Sowthistle (Sonchus oleraceus) 2014 5 herbicide fallow

Red brome (Bromus rubens) 2014 1 herbicide fallow

Sweet summer grass (Moorochloa eruciformis) 2014 1 herbicide fallow

Prickly lettuce (Lactuca serriola) 2014 1 herbicide fallow

Feathertop Rhodes grass (Chloris virgata) 2015 4 herbicide fallow; roadsides

Tridax daisy (Tridax procumbens) 2016 1 (Ord Irrig) herbicide fallow; channels

Winter grass (Poa annua) 2017 3* golf courses

Wild / willow-leaved lettuce (Lactuca saligna) 2017 2 vegetables

Northern barley grass (Hordeum glaucum) 2018 1 fences, buildings

# stopped counting; * Multiple Resistance 2,3,5,9,25

Increase in GR in 7 years

Country Number of species Country Number of species

2011 2018 2011 2018

USA 11 17 Australia 5 17

Canada 1 6 Czech

Republic

1 1

Brazil 5 8 Israel 2 2

Argentina 3 11 South

Africa

3 3

Chile 1 1 China 2 2

Spain 5 5 Malaysia 2 2

France 2 3 Italy 1 3

Resistance to glyphosate

Palmer amaranth 3x of glyphosate at 32 oz/ac

Glyphosate-resistant Palmer

1. High level of resistance

2. Trait that is nuclear encoded

3. Transferred through pollen flow

4. Potential for transfer to other amaranth species

5. Few alternative modes of action

Why is glyphosate resistant Palmer amaranth a big deal?

Glyphosate-resistant Palmer

Tranel, UI

10X copy number = Survived 4X label rate

3200 g a.e./ha

88 oz/ac

Glyphosate-resistant Kochia

M. VanGessel, UD

Resistant and susceptible horseweed following glyphosate application.

Glyphosate-resistant horseweed

Video by C Vanhorn Traps herbicide in dead leaves

Glyphosate-resistant giant ragweed

Species Country Mechanism First Year

Acalypha australis Asian Copperleaf

China 2011

Amaranthus quitensis Pigweed (quitensis)

Bolivia 2005

Amaranthus tuberculatus Common Waterhemp

United States Target and multiple SOA

2001

Ambrosia artemisiifolia Common Ragweed

United States Target and multiple SOA

2001

Descurainia sophia Flixweed

China 2011

Euphorbia heterohylla Wild Poinsettia

Brazil Multiple SOA 2004

Resistance to PPO inhibitors Group 14 herbicides

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Agricultural use

Roundup ready crop

Glyphosate resistance

0

420 g

4.2 g 0.42 g

42 g

Front row: Sensitive Back row: Resistant

Resistance to PPO inhibitors

Cobra (ai ha-1) dose response

M Normal PPX2

Gly

Resistant PPX2 has a codon deletion of glycine at position 210

With extra 90 bp at the 5’ end provide for dual targeting

M Dual targeted resistant PPX2 M

Origin of Resistance is in Mitochondria

PPO protein transport

acetolactate synthase

Acetolactate synthase (ALS) is involved in the biosynthesis of the branch-chain amino acids (valine, leucine, and isoleucine)

ALS is the target site of many herbicides that provide broad spectrum weed control at extremely low concentrations

Plants tend to evolve resistance to ALS inhibitors very rapidly

Symptoms include malformation, stunting, and reduced seed production

Effect of cloransulam-methyl on wild-type and resistance giant ragweed

pyruvate

valine isoleucine

2-ketobutyrate

leucine

2-aceto-2-hydroxybutyrate

2,3-dihydroxy-3-methylvalerate

NADPH

pyruvate

2-acetolactate

2,3-dihydroxy-3-isovalerate

NADPH

pyruvate

Resistance to ALS inhibitors

Area (×106 ha) treated with specific synthetic auxin herbicide active ingredients reported in 2014 (Dow AgroSciences proprietary sources, 2014).

Busi et al 2018 Weed resistance to synthetic auxin herbicides. Pest Manag. Sci. 2018, 74, 2265-2276

Resistance to PGR

– MOA does not result from interactions with a single gene product

– Multiple sites of action

– Resistance develops as a quantitative trait

– Multiple genes must be stacked together in order to develop resistance

– Very difficult to maintain resistance because of influx of susceptible pollen

– Multiple gene mutations could result in reduce fitness

RESISTANCE SLOW TO DEVELOP

Resistance to PGR

Multiple herbicide resistance

• Illinois waterhemp population has 4-way

resistance: Glyphosate, ALS, PPO, atrazine

• Kansas Kochia has glyphosate, ALS, atrazine,

Dicamba

• Other waterhemp populations resistant to HPPD

and 2,4-D

• No new modes of action in near future

• Have to sustain available herbicide resources

PSII Resistance

ALS Resistance PGR susceptible

Multiple resistance kochia

PRE • Scoparia – HPPD, 27 • Authority MTZ – PPO + PSII,

14 + 5 • Fierce – PPO + VLCFAE, 14 +

15 • Spartan – PPO, 14 • Clarity – auxin*, 4 • Atrazine – PSII, 5 • Linex – PSII, 7 • Corvus – ALS + HPPD, 2 + 27 • Zidua – VLCFAE, 15

Post • Clarity – auxin*, 4 • Starane – auxin, 4 (no R yet in CO • Sharpen – PPO, 14 • Impact – HPPD, 27 • Laudis – HPPD, 27 • Roundup* - EPSPS, 9 • Liberty – GS, 10 • Diflexx* – dicamba, 4 • Gramoxone – PSI, 22

Kochia can be resistant to Group 2; 5, 6, 7; 9; and 4

Kochia herbicides

MANAGEMENT OPTION LOW RISK MODERATE RISK HIGH RISK

Herbicide mix or rotation in cropping system

> 2 modes of action 2 modes of action 1 mode of action

Weed control in cropping system

Cultural*, mechanical and chemical

Cultural and chemical Chemical only

Use of same mode of action per season

Once More than once Many times

Cropping system Full rotation Limited rotation No rotation

Resistance status to mode of action

Unknown Limited Common

Weed infestation Low Moderate High

Control in last three years Good Declining Poor

Resistance risk assessment

https://hracglobal.com/

1- Has the same herbicide or herbicides with the same mechanism of action been used for several years? 2- Has the uncontrolled weed been successfully controlled by the same herbicide in previous years? 3- Are there live weeds beside dead weeds of the same species following a herbicide application? 4- Has a decline in control been noticed in recent years? 5- Are there resistant weeds in local fields, roadsides, farms, etc.? 6- Are other species in the same location being adequately controlled by your herbicide application?

Resistance risk assessment

With a number of ‘yes’ answers and other factors ruled out, resistance may be strongly suspected. At this point, leave a small area of weeds to collect whole plant or seed samples to test so resistance can be determined.

https://hracglobal.com/

Integrated Weed Management Chemical Applying herbicides to a crop

Mechanical Cultivation or ploughing to control emerged plants and bury non-germinated seed. It also includes harvest weed seed destruction such as stubble burning and cutting for hay or silage to prevent the weeds from setting seed.

Cultural Altering the crop planting date, row spacing and harvest timing to disrupt the weed cycle. It also includes planting crops that can out-compete weeds, buying certified seed that’s free of weeds and using a diverse crop rotation. Growers should also sanitize farm equipment when moving between fields.

https://hracglobal.com/

Biological Introduce insects and pathogens that control target weed species and introducing post-harvest grazing of growing weeds. Using a diversified crop rotation allows farmers to use these different weed techniques. Avoid successive crops that use herbicides with the same mechanism of action to control the same weed species in the same field.

Herbicide rotation and mixture

Use mixtures or sequential treatments of herbicides - Herbicide in the mixture should have different MOA, but target the same weed species - Consider all chemical control options before planting, in-crop and after harvest

Herbicide mixtures and herbicide rotations alone are not enough to prevent resistance. They must be used in a diversified plan than also incorporates mechanical, cultural and biological practices.

Avoid continued use of the same herbicides -That includes different herbicides with the same site of action, unless integrated with other weed control practices -Limit the number of applications of a single herbicide or herbicides with the same site of action in a single growing season

https://hracglobal.com/

1. High seeding rate

2. Narrow row spacing

3. E-W orientation

4. Competitive cultivar

Crop competition/agronomy

Barley

‘Stacking’ effective agronomic practices for sustainable weed management

Crop competition/agronomy

Northern Great Plains 10: Maintaining a database: invaluable reference

9: Strategic tillage: if, where, or when needed

8: Field & site-specific weed mgmt: 1 size may not fit all

7: Weed sanitation: border control and slowing HR dispersal

6: In-crop wheat-selective herbicide rotation: combating NTSR

5: Herbicide gp rotation: avoid back-to-back in-crop gp A or B

4: Herbicide mixtures/sequences: better than rotations

3: Pre- and post-herbicide scouting: know your enemy

2: Competitive crops & practices that promote competitiveness:

natural biological control

1: Crop diversity

Top 10 HRWM practices

Beckie and Harker 2017 Our top 10 herbicide-resistant weed management practices. Pest Manag. Sci.73, 1045-1052

Questions