Evaluating Chemical Fallow Herbicides for Potential use in

Controlling Glyphosate Resistant Kochia

Fabian Menalled & Ed DavisDecember, 2012

Project Justification• During the 2012 growing season there has been several

complains on kochia control failure with glyphosate

• Glyphosate resistant kochia has not yet been confirmed

in Montana, but it has been observed in Kansas, South

Dakota, North Dakota, Nebraska, and Alberta (Canada)

• At MSU, we are currently screening kochia seedlings to

confirm or reject the presence of glyphosate resistant

kochia

Glyphosate Resistance

• Worldwide: 24 species

• USA: 14 species

• Multiple resistance

– 2 Mode of Actions: 17 biotypes

– 3 Mode of Actions: 5 biotypes

– 4 Mode of Actions: 1 biotype

Source: www.weedscience.org, Checked Dec. 13, 2012

Confirmed glyphosate-resistant weed populations

Source: Heap 2012

Why is Kochia Such a Problem?

• Very competitive

• Extremely drought tolerate

• Late maturing

• Genetically diverse

• Out-crosses

• Over 50,000 seeds/plant

• Tumbleweed

• Herbicide resistancePNW Weed Management Handbook

Objectives• Evaluate soil active herbicides for kochia control

in a fallow period in anticipation of glyphosate

resistant kochia biotype occurrence in MT

• Achieve control of kochia seedling through mid-

July

– Kochia seed germination and seedling

establishment after mid-July is unlikely due to dry

upper soil profile

Herbicide Selection Criteria

• Early application (spring burndown)

• Soil residual activity

• Treatments:

– Gramoxone Super (burndown) & Atrazine, Sencor, Corvus (residual)

– Valor, Spartan, and Spartan Charge (burndown & residual)

– Glyphosate

• Percentage control evaluated 45 & 73 days after application

• Winter wheat: seeded in fall of 2012 to evaluate fallow

treatment effects on the crop

Amsterdam, MT

Chem fallow, no-till

Application: May 1, 2012

Perc

enta

ge C

ontr

ol

LSD = 7.39

Perc

enta

ge C

ontr

ol

LSD = 7.39LSD = 8.35

Approximate Price(Source 2012 North Dakota Weed Control Guide)

Treatment Cost $/A (high rate)Roundup 7.50Select 7.50Gramoxone Super 11.50Gramoxone Super + Atrazine 15.50Gramoxone Super + Sencor 75 DF 19.50 Gramoxone Super + Atrazine + Sencor 75DF 23.50Gramoxone Super + Corvus 42.30Gramoxone Super + Corvus + Sencor 50.30Select + Valor 24.00Select + Spartan 35.65Select + Spartan Charge + Valor 50.96Select + Spartan + Distinct 61.65

Gramoxone (paraquat)

• Restricted use pesticide

• Acute toxicity

– Fatal if inhaled. May be fatal is swallowed. Harmful in

contact with skin.

• Worldwide: 25 resistant species (43 resistant

biotypes) in 13 countries

• Australia: multiple resistance with glyphosate

Preventing the spread of herbicide resistant kochia

• Be alert!

Preventing the spread of herbicide resistant kochia

• Be alert!• Prevent weed seed production

Short wheat variety

High weed seed production

Tall wheat variety

Low weed seed production

Source: Menalled and Miller

Preventing the spread of herbicide resistant kochia

• Be alert!• Prevent weed seed production• Prevent the spread of weed seeds

Weeds are Distributed in Patches

After H. Beckie, Agri-Food Canada @ Saskatoon

Standard weed management conducted at the field level

270% expansion over 6 years

1997 2002

Standard weed management + weed shed prevention

24% expansion over 6 years

1997 2002

Preventing the spread of herbicide resistant kochia

• Be alert!• Prevent weed seed production• Prevent the spread of weed seeds• Develop and Integrated Weed Management

program to reduce the selective pressure towards the selection of herbicide resistant biotypes

http://www.ipm.montana.edu/CropWeeds/

http://www.ipm.montana.edu/CropWeeds/

In Summary• Several treatments provided kochia control through

mid summer without the use of glyphosate

• Glyphosate will still be required to control volunteer

cereal grain, weedy grasses and other broadleaf

weed species as well as susceptible kochia

• Extra cost

• Health and environmental issues

Contact us:

Fabian Menalled

719 Leon Johnson Hall

Montana State University

Bozeman, MT 59717

menalled@montana.edu

406-994-4783