<b>HRAC Group 2</b> <font size='2'> (Legacy B) </font> resistant Rumex obtusifolius from France

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 2 (LEGACY B) RESISTANT BROAD-LEAVED DOCK
(Rumex obtusifolius)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

France, Western France

INTRODUCTION		BROAD-LEAVED DOCK
Broad-Leaved Dock (Rumex obtusifolius) is a dicot weed in the Polygonaceae family. In France this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2017 and infests Wheat. Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ). Research has shown that these particular biotypes are resistant to florasulam, metsulfuron-methyl, and thifensulfuron-methyl and they may be cross-resistant to other Group 2 (Legacy B) herbicides. The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS (last updated Nov 19, 2019 )
Common Name	Broad-Leaved Dock
Species	Rumex obtusifolius
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	florasulam, metsulfuron-methyl, and thifensulfuron-methyl
Location	France, Western France
Year	2017
Situation(s)	Wheat
Contributors - (Alphabetically)	Christophe Délye
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NOTES ABOUT THIS BIOTYPE

MECHANISM

Christophe Délye

Strong resistance to SU herbicides (metsulfuron, thifensulfuron) and to the TP (florasulame). This is TSR (ALS mutant is Trp574Leu).

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Broad-Leaved Dock biotype with this Broad-Leaved Dock biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on HRAC Group 2 resistant Broad-Leaved Dock have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

Studies on the mechanism of resistance of Group 2 (Legacy B) resistant Broad-Leaved Dock from France indicate that resistance is due to an altered target site. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group 2 (Legacy B) resistant Broad-Leaved Dock from France please update the database.

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CONTRIBUTING WEED SCIENTISTS

CHRISTOPHE DÉLYE

Chargé de Recherches INRA Agroécologie 17 rue de Sully Dijon, F-21000, Burgundy France Email Christophe Délye Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in France have been instrumental in providing you this information. Particular thanks is given to Christophe Délye for providing detailed information.

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Herbicide Resistant Broad-Leaved Dock Globally
(Rumex obtusifolius)

Country

FirstYear

Situation

Active Ingredients

Site of Action

France

2017

Wheat

florasulam, metsulfuron-methyl, and thifensulfuron-methyl

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Literature about Similar Cases

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Dixon, F. L. ; Clay, D. V. ; Willoughby, I.. 2006. The efficacy of pre-emergence herbicides on problem weeds in woodland regeneration. Crop Protection 25 : 259 - 268.

Weeds germinating from seed are serious competitors for resources with young trees and can delay or prevent woodland establishment and regeneration. However, there is only limited information available on which pre-emergence herbicides are effective on problem weeds that commonly occur in these situations, in particular for perennial species germinating on fertile ex agricultural sites. Following previously reported glasshouse screening experiments for potentially useful herbicide treatments, ten residual herbicide treatments were tested on twelve problem weed species in the field. The results showed considerable variations in the susceptibilities of weed species to the different herbicide treatments. The combination of atrazine plus cyanazine, included as a standard herbicide mix that is commonly used in forestry situations, was the most effective treatment overall, with most weed species appearing to be susceptible or moderately susceptible. Chamerion angustifolium (rosebay willowherb) was the most sensitive species tested, being well controlled by the mixture of atrazine plus cyanazine, metazachlor, the higher doses of napropamide, and the mixture of metazachlor plus pendimethalin. Cirsium arvense (creeping thistle) was susceptible to isoxaben, and atrazine plus cyanazine. Clematis vitalba (old man's beard) was susceptible to isoxaben. Senecio vulgaris (groundsel) was well controlled by atrazine plus cyanazine, and metazachlor. Ranunculus repens (creeping buttercup) only appeared to be controlled by napropamide. Rumex obtusifolius (broadleaved dock) and Urtica dioica (common nettle) were susceptible to pendimethalin. Rubus fruticosus agg. (bramble), Cirsium vulgare (spear thistle), Senecio jacobea (common ragwort) and Trifolium repens (white clover) were only susceptible to the mixture of atrazine plus cyanazine. Brassica napus ssp. oleifera (volunteer oilseed rape) was not completely controlled by any of the treatments, although atrazine plus cyanazine did give significant growth reductions. A comparison of the susceptibility implied by existing literature, glasshouse pot experiments and the field trials reported here, shows the importance of confirming results obtained in pot trials with field testing and provides valuable information on efficacy which will be useful in assisting herbicide selection in the future..

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