International Survey of Herbicide-Resistant Weeds

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Status of Herbicide Resistance in Montana - Prashant Jha : January, 2014

Increasing herbicide-resistant strains of kochia, Russian thistle, wild oat, and Persian darnel are evident in Montana farm fields. Wild oat resistance to multiple modes of action including ACCase- and ALS-inhibitor herbicides is of increasing concern for predominantly cereal-based cropping systems of Montana. Furthermore, the recent evolution of glyphosate-resistant kochia (first weed to develop glyphosate resistance in Montana) and presence of auxinic (dicamba and fluroxypyr)- and ALS-inhibitor-resistant kochia is a potential threat to Montana cropping systems. Kochia resistance to auxinic herbicides was found in a few Montana wheat fields in 1995, although the extent of infestation is limited. Glyphosate and ALS-inhibitor (multiple-resistant) kochia biotypes were found in chem-fallow (wheat-fallow rotation) fields in northern Montana (2012/2013) and expected to be more widespread in occurence. Further spread of glyhosate-resistant kochia is a potential threat to the sustainability of glyphosate-resistant (Roundup Ready®) crops including corn, alfalfa, and sugar beet grown in Montana. More importantly, there is lack of POST herbicides in sugar beet production other than glyphosate and triflusulfuron (ALS-inhibitor herbicide) which are effective on kochia. Therefore, it is crucial for sugar beet growers to better manage the resistant weed seed bank in crops (corn, wheat/barley: more effective alternative modes of action available) grown in rotation with glyphosate-resistant sugar beet.

Herbicide Resistant Weeds in Montana, United States.
#YearSpeciesSite of ActionActivesContacts
1 414Kochia1984Kochia scoparia
Kochia
United States
(Montana)
MontanaMT Photosystem II inhibitors (C1/5) Photosystem II inhibitors (C1/5) atrazine Alvin Bussan
2 411Russian-thistle1987Salsola tragus
Russian-thistle
United States
(Montana)
MontanaMT ALS inhibitors (B/2) ALS inhibitors (B/2) chlorsulfuron Alvin Bussan
3 420Kochia1989Kochia scoparia
Kochia
United States
(Montana)
MontanaMT ALS inhibitors (B/2) ALS inhibitors (B/2) chlorsulfuron, metsulfuron-methyl Alvin Bussan
4 412Wild Oat1990Avena fatua
Wild Oat
United States
(Montana)
MontanaMT Cell elongation inhibitors (Z/8), Lipid Inhibitors (N/8) Multiple Resistance: 2 Sites of Action
Cell elongation inhibitors (Z/8)
Lipid Inhibitors (N/8)
difenzoquat, triallate Alvin Bussan
5 557Persian Darnel1993Lolium persicum
Persian Darnel
United States
(Montana)
MontanaMT ACCase inhibitors (A/1) ACCase inhibitors (A/1) diclofop-methyl Alvin Bussan
6 532Kochia1994Kochia scoparia
Kochia
United States
(Montana)
Montana  Synthetic Auxins (O/4) Synthetic Auxins (O/4) dicamba, fluroxypyr Bill Dyer, Alvin Bussan
7 558Wild Oat1996Avena fatua
Wild Oat
United States
(Montana)
MontanaMT ALS inhibitors (B/2) ALS inhibitors (B/2) imazamethabenz-methyl Bill Dyer
8 5246Wild Oat2002Avena fatua
Wild Oat
United States
(Montana)
Montana  ACCase inhibitors (A/1) ACCase inhibitors (A/1) clodinafop-propargyl, diclofop-methyl, fenoxaprop-P-ethyl, tralkoxydim Alvin Bussan, Jeffery Brennan
9 7804Green Foxtail2005Setaria viridis
Green Foxtail
United States
(Montana)
Montana  ACCase inhibitors (A/1) ACCase inhibitors (A/1) diclofop-methyl, fenoxaprop-P-ethyl, fluazifop-P-butyl, pinoxaden, sethoxydim Bill Dyer
10 5711Kochia2012Kochia scoparia
Kochia
United States
(Montana)
Montana  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Prashant Jha
11 7810Kochia2013Kochia scoparia
Kochia
United States
(Montana)
Montana  ALS inhibitors (B/2), EPSP synthase inhibitors (G/9) Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
glyphosate, metsulfuron-methyl, thifensulfuron-methyl, tribenuron-methyl Prashant Jha
12 11011Horseweed2015Conyza canadensis
Horseweed
United States
(Montana)
Montana  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Tim Fine, Fabian Menalled
13 12032Russian-thistle2015Salsola tragus
Russian-thistle
United States
(Montana)
Montana  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Prashant Jha, Vipan Kumar
14 15071Downy Brome (Cheatgrass)2016Bromus tectorum
Downy Brome (Cheatgrass)
United States
(Montana)
Montana  ALS inhibitors (B/2) ALS inhibitors (B/2) imazamox, procarbazone-sodium, pyroxsulam Prashant Jha, Vipan Kumar
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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Saturday, September 21, 2019 .  Available  www.weedscience.org
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