International Survey of Herbicide-Resistant Weeds

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Status of Herbicide Resistance in Idaho - Donn Thill : January, 2014

In north Idaho, the serious herbicide resistant weed is Italian ryegrass. There are biotypes resistant to all group 1 herbicides, most group 2 and flufenacet (15). Other biotypes have a mixed bag of resistance; resistance to several group ones, but not cethodim or pinoxadim. Nearly 75% of ryegrass infestation are resistant to the older group 1 herbicides – those listed in the table. Group 2 resistance is becoming more common. We are relying group 15; flufenacet and pyroxosulfone (to be registered soon). So far there is no cross resistance reported to the two group 15 herbicides. In southern Idaho, the most serious herbicide resistant weed is likely kochia.

Herbicide Resistant Weeds in Idaho, United States.
#YearSpeciesSite of ActionActivesContacts
1 230Prickly Lettuce1987Lactuca serriola
Prickly Lettuce
United States
(Idaho)
Idaho  ALS inhibitors (B/2) ALS inhibitors (B/2) chlorsulfuron, imazethapyr, metsulfuron-methyl, thifensulfuron-methyl, triasulfuron, tribenuron-methyl Donn Thill
2 232Kochia1989Kochia scoparia
Kochia
United States
(Idaho)
IdahoID ALS inhibitors (B/2) ALS inhibitors (B/2) chlorsulfuron Donn Thill
3 512Russian-thistle1990Salsola tragus
Russian-thistle
United States
(Idaho)
IdahoID ALS inhibitors (B/2) ALS inhibitors (B/2) chlorsulfuron Donn Thill
4 519Italian Ryegrass1991Lolium perenne ssp. multiflorum
Italian Ryegrass
United States
(Idaho)
Idaho  ACCase inhibitors (A/1) ACCase inhibitors (A/1) clodinafop-propargyl, diclofop-methyl, quizalofop-P-ethyl, sethoxydim Steven Seefeldt, Donn Thill
5 235Wild Oat1992Avena fatua
Wild Oat
United States
(Idaho)
IdahoID ACCase inhibitors (A/1) ACCase inhibitors (A/1) clodinafop-propargyl, diclofop-methyl, fenoxaprop-P-ethyl Donn Thill
6 234Wild Oat1993Avena fatua
Wild Oat
United States
(Idaho)
IdahoID 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 Donn Thill
7 524Mayweed Chamomile1997Anthemis cotula
Mayweed Chamomile
United States
(Idaho)
Idaho  ALS inhibitors (B/2) ALS inhibitors (B/2) chlorsulfuron, imazethapyr, thifensulfuron-methyl, tribenuron-methyl Steven Seefeldt, Donn Thill
8 1058Kochia1997Kochia scoparia
Kochia
United States
(Idaho)
IdahoID Synthetic Auxins (O/4) Synthetic Auxins (O/4) dicamba Don Morishita
9 5280Italian Ryegrass2005Lolium perenne ssp. multiflorum
Italian Ryegrass
United States
(Idaho)
Idaho  ACCase inhibitors (A/1), ALS inhibitors (B/2), Long chain fatty acid inhibitors (K3/15) Multiple Resistance: 3 Sites of Action
ACCase inhibitors (A/1)
ALS inhibitors (B/2)
Long chain fatty acid inhibitors (K3/15)
clethodim, clodinafop-propargyl, diclofop-methyl, flufenacet, quizalofop-P-ethyl, triasulfuron Donn Thill
10 5293Redroot Pigweed2005Amaranthus retroflexus
Redroot Pigweed
United States
(Idaho)
Idaho  Photosystem II inhibitors (C1/5) Photosystem II inhibitors (C1/5) metribuzin Pamela Hutchinson
11 9945Kochia2014Kochia scoparia
Kochia
United States
(Idaho)
Idaho  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Don Morishita, Prashant Jha
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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Saturday, December 7, 2019 .  Available  www.weedscience.org
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