Herbicide Resistance: Implications for Weed Management in Wheat

Drew Lyon – Endowed Chair, Small Grains Extension & Research, Weed Science

Charles Darwin

On The Origin of Species by Means of Natural Selection, or

The Preservation of Favoured Races in the Struggle for Life

Requirements for Natural Selection

A struggle for existence

Variation

Inheritance

Herbicide Resistance is a Case Studyon Natural Selection

Progression of Weed Resistance

Treatment

% Resistant

Weeds in

Population

Weed

Control

0 Application .0001 Excellent

1st Application .00143 Excellent

2nd Application .0205 Excellent

3rd Application .294 Excellent

4th Application 4.22 Excellent

5th Application 60.5 Failure

Weed resistance progresses logarithmically

Year 0

First application of herbicide to the initial population

seed pool or seed bank in soil

Herbicide-resistant biotype

Year 1Year 2

After first application, the resistant individual survives the treatment and produces seed

Control is still excellent, but resistant seed continue to increase

Credit: Mike DeFelice

Treatment

% Resistant

Weeds in

Population

Weed

Control

0 Application .0001 Excellent

1st Application .00143 Excellent

2nd Application .0205 Excellent

3rd Application .294 Excellent

4th Application 4.22 Excellent

5th Application 60.5 Failure

Control is still very good, but resistant seed continue to increase

Year 3

seed pool or seed bank in soil

Progression of Weed ResistanceWeed resistance progresses logarithmically

Year 4

Control may still appear acceptable, but the seed pool is almost completely composed of the resistant type

Herbicide resistance cannot be reversed in a practical time frame. In many cases, the seed pool is unlikely to change back because there is no fitness penalty.

Year 5

Weed plants and seed pool arenow mostly herbicide-resistant

Credit: Mike DeFelice

Factors Affecting Speed of Selection

7

The length of time for selection of resistance varies by : Cultural practices

Frequency of herbicide use

Herbicide mechanism of action

Year 0 Year 2 Year 4 Year 6 Year 8 Year 10 Later

Biology of weed species

Frequency of resistant biotypes among weed species

Current Status of Resistance

1. No herbicides with new mechanisms of

action are in advanced development trials.

2. The last new mechanism of action was

introduced over 30 years ago.

Du

ke

(20

12

). P

est

Man

agem

ent

Sci

ence

Cumulative a.i. Introductions versus

Issued Herbicide Patents per Year

Current Status of Resistance

1. No herbicides with new mechanisms of

action are in advanced development trials.

2. The last new mechanism of action was

introduced over 25 years ago.

3. The number of weeds with herbicide

resistance continues to increase within the

US and globally.

4. The number of weeds with herbicide

resistance to more than one herbicide

continues to increase.

weedscience.org

Current Status of HerbicideResistance in the PNW

Species MOA

Common Groundsel Group 5 (simazine), Group 6 (bromoxynil)

Prickly Lettuce Group 2 (ALS), Group 4 (synthetic auxins)

KochiaGroup 2 (ALS), Group 4 (synthetic auxins),

Group 9 (glyphosate),

Russian Thistle Group 2 (ALS), Group 9 (glyphosate)

Mayweed Chamomile Group 2 (ALS)

Redroot Pigweed Group 5 (photosystem II)

Spiny Sowthistle Group 2 (ALS)

Common Lambsquarters Group 5 (photosystem II)

Yellow Starthistle Group 4 (synthetic auxins)

Downy Brome Group 1 (ACCase), Group 2 (ALS)

Italian Ryegrass

Group 1 (ACCase), Group 2 (ALS), Group 15

(flufenacet),

Group 9 (glyphosate), Group 10 (glufosinate)

Wild Oat Group 1 (ACCase), Group 3 (pronamide), Group 8,

Group 26 (difenzoquat, triallate)

Glyphosate Dose Response - Average Dry Weight Reductions

Dose Response Picture Gallery

Dose Response Picture Gallery

Dose Response Picture Gallery

Dose Response Picture Gallery

Dose Response Picture Gallery

How Do We Avoid or Delay Herbicide Resistance in Weeds?

Sanitation Mechanical

Chemical

Cultural

Biological

Integrated Weed Management

General Principles of Integrated Weed Management

Use agronomic practices that limit the introduction and spread of weeds

“Prevent weed problems before they start”

Help the crop compete with weeds

Help crop “choke out” weeds

Use practices that keep weeds “off balance”

“do not allow weeds to adapt”

Prevent Weed ProblemsBefore They Start

Use clean seed

Tarp grain loads

Control weeds on field edges

Remove or cut weeds before seed set

Compost livestock manure

Manage weed seed at harvest and after harvest

Weed Seeds at Harvest

Majority of weed seeds exit in the

chaff fraction

Narrow Windrow Burning

Most Western Australian growers use this technique

99% control of Lolium and Raphanus

Windrows vs. Field Burning

Italian Ryegrass Seed Survival

0

5

10

15

20

25

30

35

40

Spread/No Burn Spread/Burn Windrow/Burn

No

. of

see

dlin

gs e

me

rge

d

2013 2014

0*

036

37

502 584

No Burn vs. Burn P=0.003Spread vs. Windrow P=0.002

No Burn vs. Burn P<0.001Spread vs. Windrow P<0.001

* Seconds above 392° F (200o C)

Alternatives to Field Burning

Chaff Collection

Up to 85% of Lolium and Raphanus seed collected and removed

Bale Direct Systems

Integrated Impact Mill Systems

Chaff Lining

Tram Lining

Harvest Weed Seed Control

Biological attribute needed for system to work:mature seed do not shatter before grain harvest, held above

cutting bar height

Italian Ryegrass Seed Retention in Winter Wheat – 2017 & 2018

0

10

20

30

40

50

60

70

80

90

100

6-Jul 11-Jul 18-Jul 27-Jul 1-Aug

Seed

ret

enti

on

(%

)

Sample date

Three sites each year & three sampling locations at each site.

Help Crop “Choke Out” Weeds

Fertilizer placement and/or timing

High seeding rates

Narrow row spacing

Shallow and uniform seeding

High quality seed

Well prepared seedbed

Competitive crop varieties

Do Not Allow Weeds to Adapt

Crop rotation

Select crops with varied seeding dates

Select crops with varied life cycles

Alternate crops with varied competitive abilities

Rotate and/or combine herbicides with different mechanisms of action AND activity on the same target weeds

Annual Ryegrass Seed Persistence

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7

Seed

via

bili

ty (

%)

Years after burial

WD 1 WD 3 WD 7 PD 1 PD 3 PD 7

Adapted from Rampton and Ching, 1970. Persistence of crop seeds in soil. Agron. J. 62: 272-277.

smallgrains.wsu.edu

• Pulse Crop MOA Tool• Wheat MOA Tool

Do Not Allow Weeds to Adapt

Crop rotation

Select crops with varied seeding dates

Select crops with varied life cycles

Alternate crops with varied competitive abilities

Rotate and/or combine herbicides with different mechanisms of action

Rotate use of Herbicide-Resistant Crops

Rotate tillage practices

Risk of Resistance on aPer Species Basis

Moss 1998

Management Option: Low Moderate High

Herbicide mix or rotation in cropping system

> 2 modes of action

2 modes of action 1 modes of action

Weed control in cropping system

Cultural, mechanical,

and chemical

Cultural and chemical

Chemical alone

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 3 years Good Declining Poor

Italian Ryegrass

• Obligate outcrossing species– Wide genetic variation– Pollen can move resistance

• Resistant to every labeled mode of action– Glyphosate resistance in

orchards

• Some populations in Australia are resistant to 6 sites of action

Italian Ryegrass Control – Winter Wheat

• Use a soil-applied VLCFA synthesis inhibitor (Group 15) herbicide in the fall

– pyroxasulfone (Zidua)

– pyroxasulfone + carfentrazone (Anthem Flex)

– flufenacet + metribuzin (Axiom)

• Follow with a POST ALS inhibitor (Group 2) herbicide in the spring

– pyroxsulam (PowerFlex HL, TeamMate)

– flucarbazone (Everest 3.0, Sierra)

– mesosulfuron (Osprey)

Italian Ryegrass Control with Pyroxasulfone

Italian ryegrass control Winter wheat yield

Treatment Rate Timing 2017 2018 2017 2018

g ai ha-1 -------------- % -------------- ---------- kg ha-1 ----------

Nontreated check --- --- --- --- 2220 b 1880 d

Pyroxasulfone 90 PRE 75 e 86 ab 6920 a 6450 a

Pyroxasulfone 90 DPRE 81 cde 75 c 6790 a 5850 ab

Pyroxasulfone + metribuzin 90 + 76 DPRE 79 de 75 c 6990 a 5240 bc

Pyroxasulfone 150 Spike leaf 90 abc 81 bc 6850 a 6250 ab

Pyroxasulfone + pyroxsulam

150 + 18 Spike leaf 89 abc 88 ab 5580 a 5910 ab

Pyroxasulfone 150 Tillering 30 f 40 d 2690 b 4170 c

Pyroxasulfone + pyroxsulam

150 + 18 Tillering 27 f 35 d 2960 b 4100 c

Pyroxasulfone + pyroxasulfone

9060

PRESpike leaf

95 a 91 ab 6450 a 6050 ab

Pyroxasulfone + Pyroxasulfone + pyroxsulam

90 60 + 18

PRESpike leaf

91 ab 93 a 5980 a 6120 ab

Pyroxasulfone + Pyroxasulfone

9060

PRETillering

79 de 94 a 6320 a 5850 ab

Pyroxasulfone + Pyroxasulfone + pyroxsulam

9060 + 18

PRETillering

85 bcd 91 ab 6920 a 5640 ab

Italian Ryegrass Control – Spring Wheat

• Consider the following:– Not growing spring wheat

– Baling winter wheat straw in the fall prior to spring wheat seeding

– Delayed seeding• Barley may be a better choice for delayed seeding

– Shallow fall tillage after harvest to stimulate germination before planting the next spring crop

• Use an ACCase inhibitor (Group 1) herbicide for POST control

– Use a den or fop

• pinoxaden (Axial XL)

• clodinafop (Discover NG, NextStep NG, Observe)

• fenoxaprop (Double Check, Parity, Tacoma 1EC)

Non-baled vs. Baled Straw

400 Italian ryegrass plants/ft2

Non-baled vs. Baled Straw

0

10

20

30

40

50

60

70

80

Non-baled Baled

Ital

ian

rye

gras

s ca

no

py

cove

r at

har

vest

(%

)

No Zidua Zidua

Italian Ryegrass Control – Garbanzo Beans

• Several good soil-applied herbicides available

– metolachlor (Dual Magnum)

– dimethanamid (Outlook)

– triallate (Avadex, Far-Go)

– pendimethalin (Prowl, Prowl H2O) - or + metribuzin (Tripzin ZC)

• Use ACCase inhibitor (Group 1) herbicide for POST control

– Use a dim

• Clethodim (Select 2EC, Select Max)

• Consider deep plowing in areas with heavy infestations

Italian Ryegrass Control - Canola

• PPI– ethalfluralin (Sonalan)

– Trifluralin (Treflan)

• POST – quizalofop-p-ethyl (Assure II)

– Sethoxydim (Poast)

– Clethodim (Select 2EC, Select Max)

• RR canola: POST – glyphosate

• apply early at maximum allowable rate

Non-labeled Uses

Some of the pesticides discussed in this presentation were tested under an experimental use permit granted by WSDA. Application of a pesticide to a crop or site that is not on the label is a violation of pesticide law and may subject the applicator to civil penalties up to $7,500. In addition, such an application may also result in illegal residues that could subject the crop to seizure or embargo action by WSDA and/or the U.S. Food and Drug Administration. It is your responsibility to check the label before using the product to ensure lawful use and obtain all necessary permits in advance.

Questions?