<b>HRAC Group 5</b> <font size='2'> (Legacy C1 C2) </font> resistant Atriplex patula from United States, Michigan

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 5 (LEGACY C1 C2) RESISTANT HALBERDLEAF ORACH
(Atriplex patula)

PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)

United States, Michigan

INTRODUCTION		HALBERDLEAF ORACH
Halberdleaf Orach (Atriplex patula) is a dicot weed in the Chenopodiaceae family. In Michigan this weed first evolved resistance to Group 5 (Legacy C1 C2) herbicides in 2003 and infests Corn (maize). Group 5 (Legacy C1 C2) herbicides are known as PSII inhibitors - Serine 264 Binders (Inhbition of Photosynthesis at PSll - Serine 264 Binders ). Research has shown that these particular biotypes are resistant to atrazine and they may be cross-resistant to other Group 5 (Legacy C1 C2) 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 Mar 05, 2007 )
Common Name	Halberdleaf Orach
Species	Atriplex patula
Group	PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
Herbicides	atrazine
Location	United States, Michigan
Year	2003
Situation(s)	Corn (maize)
Contributors - (Alphabetically)	Steven Gower
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Halberdleaf Orach biotype with this Halberdleaf Orach 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 5 resistant Halberdleaf Orach 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

The mechanism of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the mechanism of resistance for this biotype then please update the database.

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 5 (Legacy C1 C2) resistant Halberdleaf Orach from Michigan please update the database.

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CONTRIBUTING WEED SCIENTISTS

STEVEN GOWER

Former Weed Science Diagnostician (Now with Monsanto) Michigan State University Diagnostic Services 578 Wilson Rd. East Lansing, 48824, Michigan United States Email Steven Gower

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

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Herbicide Resistant Halberdleaf Orach Globally
(Atriplex patula)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Belgium

2015

Sugar beets

desmedipham, lenacil, metamitron, and phenmedipham

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

France

2019

Potatoes, and Sugar beets

metamitron, and metribuzin

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Germany

1980

Corn (maize)

atrazine

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

United States (Michigan)

2003

Corn (maize)

atrazine

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Literature about Similar Cases

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López, C. ; López, C. ; Murillo, S. ; Zaragoza, C. ; Prado, R. de. 1993. Annual weed populations resistant to atrazine in Aragon. : 249 - 253.

In a survey conducted in the maize-growing area of Aragon in NE Spain during 1991 and 1992, weed species were collected to investigate the extent of atrazine resistance. The survey focussed on fields repeatedly treated with atrazine. Samples of weeds suspected of atrazine resistance were subjected to laboratory tests. The slow chlorophyll fluorescence test was used to assess inhibition of photosynthesis and revealed some resistant specimens of Chenopodium album, Amaranthus retroflexus and A. hybridus. A detoxifying ecotype of Atriplex patula was also discovered. The number of atrazine-resistant weeds found was not high..

Kees, H.. 1988. The development of triazine-resistant annual weeds in Bavaria and experience with their control. Gesunde Pflanzen 40 : 407 - 412, 414.

The first evidence of weed resistance to triazine herbicides in Bavaria occurred in the period 1975-80 in intensive maize growing areas following continuous treatment with atrazine. Resistance was shown by Stellaria media, Solanum nigrum, Chenopodium album and Galinsoga ciliata, with Atriplex patula and C. ficifolium being largely unaffected. Since 1982 there has been a sharp increase in the areas affected by resistant species which included for the first time Amaranthus retroflexus, Senecio vulgaris and, in isolated instances, C. polyspermum; Polygonum lapathifolium, Fallopia convoluulus, and Epilobium tetragonum also showed resistance. Since 1980, triazine-resistance has also been reported in S. vulgaris, Poa annua, C. album and A. retroflexus in horticultural crops. Control strategies to combat weed resistance are discussed..

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