International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
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Status of Herbicide Resistance in California - Brad Hanson : January, 2014

Herbicide resistance in California is currently dominated by two patterns of resistance that differ somewhat from the rest of the United States. The first major category is multiple-resistance in a number of sedge and grass weeds of the rice production region of the Sacramento Valley. Rice in these areas is typically grown under flooded conditions and is often in long-term rice monoculture due to soil and water conditions in the area which makes them heavily reliant on herbicides for weed control. These cases tend to be due to non-target site mechanisms or, in some cases, combinations of target site and non-target site mechanisms of resistance, and present a serious challenge to growers. The second broad category is glyphosate-resistant weeds in orchards, vineyards, and associated non-crop areas such as roadsides, canal banks, and field margins. Glyphosate has been the most important herbicide in these areas for several years due to efficacy, economical cost, and a favorable environmental and toxicological profile. In the past decade, several new cases of glyphosate resistance have been documented. The most widespread of these appears to be hairy fleabane which can be found nearly anywhere in the agricultural areas of the state. One important distinction between California and other regions of the US is that our cases of glyphosate-resistance are not primarily associated with Roundup Ready cropping systems but instead with non-crop uses or directed spray applications in woody perennial crops. Roundup Ready crops (cotton, maize, and recently alfalfa) are grown in California and do have some challenges with glyphosate-resistant weeds; however, tillage and irrigation practices seem to have reduced or delayed this problem in comparison to the reduced tillage row crop systems in other parts of the country.

Status of Herbicide Resistance in California - Maor Matzrafi : April, 2015

During the last couple of years we are running a survey to try and understand the magnitude of herbicide resistance in the southern part of Israel where wheat is the most common crop. We have identified some false positive herbicide resistant reports due to miss application of herbicides, especially ACCase inhibitors. Over all, the cases found are mostly based on NTS mechanism but laboratory experiments are still in progress to base those assumptions. Our Conyza canadensis have developed resistance due to two target site mutations in the ALS and PSII genes in the same individual plants (real multiple resistances). Avena sterilis also showed mutation in the ACCase gene and this population is still under investigation. After several field trials that have been conducted this year in wheat fields; we believe that the answer for the resistance in grass weeds might be pre-em treatments with VLCFA herbicides. Our goal is to convince our farmers to do so in the next few years.

Best regards, Maor and Baruch

Herbicide Resistant Weeds in California, United States.
#YearSpeciesSite of ActionActivesContacts
1 1037Common Groundsel1981Senecio vulgaris
Common Groundsel
United States
(California)
CaliforniaCA Photosystem II inhibitors (C1/5) Photosystem II inhibitors (C1/5) atrazine Jodie Holt
2 396Perennial Ryegrass1989Lolium perenne
Perennial Ryegrass
United States
(California)
CaliforniaCA ALS inhibitors (B/2) ALS inhibitors (B/2) sulfometuron-methyl Leonard Saari, Josephine Cotterman
3 390California Arrowhead1993Sagittaria montevidensis
California Arrowhead
United States
(California)
CaliforniaCA ALS inhibitors (B/2) ALS inhibitors (B/2) bensulfuron-methyl Michael Carriere
4 391Smallflower Umbrella Sedge1993Cyperus difformis
Smallflower Umbrella Sedge
United States
(California)
CaliforniaCA ALS inhibitors (B/2) ALS inhibitors (B/2) bensulfuron-methyl Michael Carriere
5 1036Russian-thistle1994Salsola tragus
Russian-thistle
United States
(California)
California  ALS inhibitors (B/2) ALS inhibitors (B/2) chlorsulfuron, sulfometuron-methyl Timothy Prather, Jodie Holt
6 1176Wild Oat1996Avena fatua
Wild Oat
United States
(California)
CaliforniaCA Cell elongation inhibitors (Z/8) Cell elongation inhibitors (Z/8) difenzoquat Steve Orloff, Jodie Holt
7 1098Eared Redstem1997Ammannia auriculata
Eared Redstem
United States
(California)
CaliforniaCA ALS inhibitors (B/2) ALS inhibitors (B/2) bensulfuron-methyl Jim Hill
8 1099Ricefield Bulrush1997Schoenoplectus mucronatus (=Scirpus mucronatus)
Ricefield Bulrush
United States
(California)
CaliforniaCA ALS inhibitors (B/2) ALS inhibitors (B/2) bensulfuron-methyl Jim Hill
9 283Late Watergrass1998Echinochloa phyllopogon (=E. oryzicola)
Late Watergrass
United States
(California)
CaliforniaCA ACCase inhibitors (A/1) ACCase inhibitors (A/1) fenoxaprop-P-ethyl Albert Fischer
10 1034Rigid Ryegrass1998Lolium rigidum
Rigid Ryegrass
United States
(California)
California  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Thomas Lanini : retired, Brad Hanson, Marie Jasieniuk
11 1035Late Watergrass1998Echinochloa phyllopogon (=E. oryzicola)
Late Watergrass
United States
(California)
CaliforniaCA Lipid Inhibitors (N/8) Lipid Inhibitors (N/8) thiobencarb = benthiocarb Albert Fischer
12 5492Early Watergrass2000Echinochloa oryzoides
Early Watergrass
United States
(California)
California  Lipid Inhibitors (N/8) Lipid Inhibitors (N/8) molinate, thiobencarb = benthiocarb Albert Fischer
13 5135Redstem2000Ammannia coccinea
Redstem
United States
(California)
California  ALS inhibitors (B/2) ALS inhibitors (B/2) bensulfuron-methyl Jim Hill
14 5136Barnyardgrass2000Echinochloa crus-galli var. crus-galli
Barnyardgrass
United States
(California)
California  ACCase inhibitors (A/1), Lipid Inhibitors (N/8) Multiple Resistance: 2 Sites of Action
ACCase inhibitors (A/1)
Lipid Inhibitors (N/8)
cyhalofop-butyl, fenoxaprop-P-ethyl, molinate, thiobencarb = benthiocarb Albert Fischer
15 5137Late Watergrass2000Echinochloa phyllopogon (=E. oryzicola)
Late Watergrass
United States
(California)
California  ACCase inhibitors (A/1), Lipid Inhibitors (N/8) Multiple Resistance: 2 Sites of Action
ACCase inhibitors (A/1)
Lipid Inhibitors (N/8)
cyhalofop-butyl, fenoxaprop-P-ethyl, molinate, thiobencarb = benthiocarb Albert Fischer
16 5163Little seed Canary grass2001Phalaris minor
Little seed Canary grass
United States
(California)
California  ACCase inhibitors (A/1) ACCase inhibitors (A/1) clethodim, fenoxaprop-P-ethyl, fluazifop-P-butyl, sethoxydim Joseph Di Tomaso
17 5134Smooth Crabgrass2002Digitaria ischaemum
Smooth Crabgrass
United States
(California)
California  Synthetic Auxins (O/4) Synthetic Auxins (O/4) quinclorac Albert Fischer
18 5250Horseweed2005Conyza canadensis
Horseweed
United States
(California)
California  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Brad Hanson, Anil Shrestha, Kurt Hembree, Steve Wright
19 5310Hairy Fleabane2007Conyza bonariensis
Hairy Fleabane
United States
(California)
California  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Brad Hanson, Anil Shrestha, Kurt Hembree, Marcelo L. Moretti
20 5545Junglerice2008Echinochloa colona
Junglerice
United States
(California)
California  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Albert Fischer, Thomas Lanini : retired, Brad Hanson, Steve Wright
21 5698Italian Ryegrass2008Lolium perenne ssp. multiflorum
Italian Ryegrass
United States
(California)
California  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Marie Jasieniuk
22 5390Hairy Fleabane2009Conyza bonariensis
Hairy Fleabane
United States
(California)
California  EPSP synthase inhibitors (G/9), PSI Electron Diverter (D/22) Multiple Resistance: 2 Sites of Action
EPSP synthase inhibitors (G/9)
PSI Electron Diverter (D/22)
glyphosate, paraquat Brad Hanson, Anil Shrestha, Kurt Hembree, Steve Wright, Marcelo L. Moretti
23 6739Smallflower Umbrella Sedge2013Cyperus difformis
Smallflower Umbrella Sedge
United States
(California)
California  PSII inhibitor (Ureas and amides) (C2/7) PSII inhibitor (Ureas and amides) (C2/7) propanil Albert Fischer, Rafael Pedroso
24 7805Annual Bluegrass2013Poa annua
Annual Bluegrass
United States
(California)
California  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Brad Hanson, Marcelo L. Moretti
25 9924Ricefield Bulrush2014Schoenoplectus mucronatus (=Scirpus mucronatus)
Ricefield Bulrush
United States
(California)
California  PSII inhibitor (Ureas and amides) (C2/7) PSII inhibitor (Ureas and amides) (C2/7) propanil Albert Fischer, Rafael Pedroso
26 9943Horseweed2014Conyza canadensis
Horseweed
United States
(California)
California  EPSP synthase inhibitors (G/9), PSI Electron Diverter (D/22) Multiple Resistance: 2 Sites of Action
EPSP synthase inhibitors (G/9)
PSI Electron Diverter (D/22)
glyphosate, paraquat Brad Hanson, Marcelo L. Moretti
27 13041Palmer Amaranth2015Amaranthus palmeri
Palmer Amaranth
United States
(California)
California  EPSP synthase inhibitors (G/9) EPSP synthase inhibitors (G/9) glyphosate Brad Hanson, Anil Shrestha, Steve Wright, Jorge Angeles, Samikshya Budhathoki , Mala To, Sonia Rios
28 13044Italian Ryegrass2015Lolium perenne ssp. multiflorum
Italian Ryegrass
United States
(California)
California  Glutamine synthase inhibitors (H/10) Glutamine synthase inhibitors (H/10) glufosinate-ammonium Marie Jasieniuk, Parsa Tehranchian
29 15066Italian Ryegrass2015Lolium perenne ssp. multiflorum
Italian Ryegrass
United States
(California)
California  ACCase inhibitors (A/1), EPSP synthase inhibitors (G/9), PSI Electron Diverter (D/22) Multiple Resistance: 3 Sites of Action
ACCase inhibitors (A/1)
EPSP synthase inhibitors (G/9)
PSI Electron Diverter (D/22)
glyphosate, paraquat, sethoxydim Brad Hanson, Marie Jasieniuk, Caio Brunharo, Parsa Tehranchian
30 17104Italian Ryegrass2016Lolium perenne ssp. multiflorum
Italian Ryegrass
United States
(California)
California  ACCase inhibitors (A/1), ALS inhibitors (B/2), EPSP synthase inhibitors (G/9), PSI Electron Diverter (D/22) Multiple Resistance: 4 Sites of Action
ACCase inhibitors (A/1)
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
PSI Electron Diverter (D/22)
clethodim, cyhalofop-butyl, fenoxaprop-P-ethyl, fluazifop-P-butyl, glyphosate, imazamox, mesosulfuron-methyl, paraquat, sethoxydim Marie Jasieniuk, Maor Matzrafi, Parsa Tehranchian
Contributing Weed Scientists
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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Monday, December 18, 2017 .  Available  www.weedscience.org
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