Herbicide Resistant Weeds

GROUP B/2 RESISTANT REDROOT PIGWEED (Amaranthus retroflexus)
Canada: Ontario

Thursday, September 09, 2010

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Redroot Pigweed

1.	Introduction
2.	Level of Infestation
3.	Quick Statistics
4.	Notes about this biotype
5.	Academic Aspects
6.	R Redroot Pigweed Globally
7.	Fact Sheets and Literature
8.	Contributing Weed Scientists
9.	Acknowledgements
10.	Where to now?

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Introduction

Level of Infestation

Redroot Pigweed (Amaranthus retroflexus) is a dicot weed in the Amaranthaceae family. In Ontario this weed first evolved resistance to Group B/2 herbicides in 1998 and infests corn, cropland, and soybean. Group B/2 herbicides are known as ALS inhibitors (Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)). Research has shown that these particular biotypes are resistant to imazethapyr, and thifensulfuron-methyl and they may be cross-resistant to other Group B/2 herbicides.

Local weed scientists estimate that Group B/2 resistant Redroot Pigweed in Ontario infests 6-10 sites and the number of sites are increasing. They also estimate that there are 501-1000 acres infested with Group B/2 resistant Redroot Pigweed.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their mode of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS ( last updated Dec 07, 2000 )
Common Name	Redroot Pigweed
Species	Amaranthus retroflexus
Group	ALS inhibitors (B/2)
Herbicides	imazethapyr, and thifensulfuron-methyl
Location	Canada, Ontario
Year	1998
Situation(s)	corn, cropland, and soybean
Sites	6-10
Acres Infested	501-1000
Contributors	Francois Tardif
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NOTES ABOUT THIS BIOTYPE

GENERAL

Hugh Beckie

Ferguson, G. M., R. S. Diebold, F. J. Tardif, and A. S. Hamill. 2000. Populations of green pigweed (Amaranthus powellii) and redroot pigweed (Amaranthus retroflexus) in Ontario show different patterns of resistance to ALS-inhibiting herbicides and to triazines. Weed Sci. Soc. Am. Abstr. 40:47-48. Also: Ferguson, G. M., A. S. Hamill, and F. Tardif. 2000. Characterization of imazethapyr and flumetsulam resistance and cross resistance to thifensulfuron-methyl in populations of Amaranthus powellii S. Wats. and A. retroflexus L. in Ontario. Abstr. Third International Weed Science Congress, Foz do Iguassu, Brazil. Corvallis, OR: International Weed Science Society. p. 152.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Redroot Pigweed biotype with this Redroot Pigweed 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 Group B/2 resistant Redroot Pigweed indicate that inheritance is determined by a one gene, semi dominant, nuclear trait. 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 B/2 resistant Redroot Pigweed from Ontario 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 B/2 resistant Redroot Pigweed from Ontario please update the database.

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HERBICIDE RESISTANT REDROOT PIGWEED GLOBALLY
#	Country	Year	Sites	Acres	Mode of Action
1.	Bulgaria	1984	11-50	1001-10000	Photosystem II inhibitors (C1/5)
2.	Bulgaria	1984	2-5	1-5	Ureas and amides (C2/7)
3.	Canada (Ontario)	1980	501-1000	501-1000	Photosystem II inhibitors (C1/5)
4.	Canada (Ontario)	1998	6-10	501-1000	ALS inhibitors (B/2)
5.	Canada (Ontario)	2001	1	unknown	Ureas and amides (C2/7)
6.	Canada (Quebec)	2001	1	unknown	Ureas and amides (C2/7)
7.	Canada (Manitoba)	2002	1	51-100	ALS inhibitors (B/2)
8.	Canada (Ontario)	2005	1	51-100	Nitriles and others (C3/6)
9.	China	1990	501-1000	101-500	Photosystem II inhibitors (C1/5)
10.	Czech Republic	1985	501-1000	1001-10000	Photosystem II inhibitors (C1/5)
11.	France	1980	unknown	unknown	Photosystem II inhibitors (C1/5)
12.	Germany Multiple Resistance	1980	51-100	51-100	Photosystem II inhibitors (C1/5) Ureas and amides (C2/7)
13.	Greece	2000	2-5	11-50	Photosystem II inhibitors (C1/5)
14.	Israel	1991	2-5	11-50	ALS inhibitors (B/2)
15.	Italy	1999	1	51-100	Photosystem II inhibitors (C1/5)
16.	Italy	2003	1	51-100	ALS inhibitors (B/2)
17.	Poland	1991	51-100	unknown	Photosystem II inhibitors (C1/5)
18.	Spain	1986	6-10	unknown	Photosystem II inhibitors (C1/5)
19.	Switzerland	1982	51-100	101-500	Photosystem II inhibitors (C1/5)
20.	USA (Indiana)	1980	501-1000	1001-10000	Photosystem II inhibitors (C1/5)
21.	USA (Colorado)	1982	501-1000	1001-10000	Photosystem II inhibitors (C1/5)
22.	USA (Connecticut)	1984	501-1000	10001-100000	Photosystem II inhibitors (C1/5)
23.	USA (New Hampshire)	1984	11-50	501-1000	Photosystem II inhibitors (C1/5)
24.	USA (Maine)	1985	51-100	1001-10000	Photosystem II inhibitors (C1/5)
25.	USA (Minnesota)	1991	1	11-50	Photosystem II inhibitors (C1/5)
26.	USA (Vermont)	1991	51-100	1001-10000	Photosystem II inhibitors (C1/5)
27.	USA (Virginia)	1993	unknown	unknown	Photosystem II inhibitors (C1/5)
28.	USA (Oregon)	1994	6-10	101-500	Photosystem II inhibitors (C1/5)
29.	USA (Arkansas)	1995	unknown	unknown	ALS inhibitors (B/2)
30.	USA (Kansas)	1995	unknown	unknown	Photosystem II inhibitors (C1/5)
31.	USA (Maryland)	1998	unknown	unknown	ALS inhibitors (B/2)
32.	USA (Pennsylvania) Multiple Resistance	1998	2-5	501-1000	ALS inhibitors (B/2) Photosystem II inhibitors (C1/5)
33.	USA (North Dakota)	1999	1	1-5	ALS inhibitors (B/2)
34.	USA (Michigan) Multiple Resistance	2001	6-10	51-100	Photosystem II inhibitors (C1/5) Ureas and amides (C2/7)
35.	USA (Idaho)	2005	2-5	501-1000	Photosystem II inhibitors (C1/5)
36.	Yugoslavia	1999	unknown	unknown	Photosystem II inhibitors (C1/5)
37.	Yugoslavia	2002	unknown	unknown	ALS inhibitors (B/2)

FACT SHEETS AND OTHER LITERATURE	Format
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Scientific Abstracts on Herbicide Resistant Amaranthus retroflexus
Mutations in ALS confer herbicide resistance in redroot pigweed (Amaranthus retroflexus) and Powell amaranth (Amaranthus powellii).
McNaughton, K. E., J. Letarte, E. A. Lee, and F. J. Tardif. 2005. Mutations in ALS confer herbicide resistance in redroot pigweed (Amaranthus retroflexus) and Powell amaranth (Amaranthus powellii). Weed Science. 53: 17-22.
An italian population of Amaranthus retroflexus resistant to ALS-inhibiting herbicides: resistance pattern and molecular basis.
Scarabel L., Varotto S., and Sattin M. 2005. An italian population of Amaranthus retroflexus resistant to ALS-inhibiting herbicides: resistance pattern and molecular basis. 13th EWRS Symposium. : Abstr. 202.
Sulfometuron-resistant Amaranthus retroflexus : cross-resistance and molecular basis for resistance to acetolactate synthase-inhibiting herbicides.
Sibony, M.; Michel, A.; Haas, H. U.; Rubin, B.; Hurle, K. 2001. Sulfometuron-resistant Amaranthus retroflexus : cross-resistance and molecular basis for resistance to acetolactate synthase-inhibiting herbicides. Weed Research. 41: 509-522.
Mutations in the ALS gene confering resistance to group II herbicides in redroot pigweed (Amaranthus retroflexus) and green pigweed (A. powellii).
McNaughton, K. E., E. Lee A., and F. Tardif J. 2001. Mutations in the ALS gene confering resistance to group II herbicides in redroot pigweed (Amaranthus retroflexus) and green pigweed (A. powellii). Weed Science Society of America Abstracts. 41: 97.
Metribuzin resistance in Amaranthus retroflexus and Chenopodium album in Greece.
Eleftherohorinos, I. G., I. Vasilakoglou B., and K. Dhima V. 2000. Metribuzin resistance in Amaranthus retroflexus and Chenopodium album in Greece. Weed Science. 48: 69-74.
Amaranthus retroflexus L. (code: AMARE).: Amaranthus retroflexus L. Amaranto comune o blito (codice: AMARE).
Campagna, G. and G. Rapparini. 1997. Amaranthus retroflexus L. (code: AMARE).: Amaranthus retroflexus L. Amaranto comune o blito (codice: AMARE). Informatore Agrario. 53: 68.
Herbicide cross-resistance in atrazine-resistant velvetleaf (Abutilon theophrasti) and redroot pigweed (Amaranthus retroflexus).
Dabaan, M. E., K. Garbutt, H. Brown (ed.), G. W. Cussans (ed.), M. D. Devine (ed.), S. O. Duke (ed.), C. Fernandez Quintanilla (ed.), A. Helweg (ed.), R. E. Labrada (ed.), M. Landes (ed.), P. Kudsk (ed.), and J. C. Streibig. 1996. Herbicide cross-resistance in atrazine-resistant velvetleaf (Abutilon theophrasti) and redroot pigweed (Amaranthus retroflexus). Proceedings of the second international weed control congress, Copenhagen, Denmark, 25-28 June 1996. 1-4: 505-510.
Molecular survey of Polish resistant biotypes of weeds.
Gadamski, G., D. Ciarka, S. W. Gawronski, H. Brown (ed.), G. W. Cussans (ed.), M. D. Devine (ed.), S. O. Duke (ed.), C. Fernandez Quintanilla (ed.), A. Helweg (ed.), R. E. Labrada (ed.), M. Landes (ed.), P. Kudsk (ed.), and J. C. Streibig. 1996. Molecular survey of Polish resistant biotypes of weeds. Proceedings of the second international weed control congress, Copenhagen, Denmark, 25-28 June 1996. 1-4: 547-550.
Physiological and biochemical characteristics in triazine resistant biotypes of four Amaranthus species.
Dominguez, C., M. Tena, R. Prado de, and R. De Prado. 1994. Physiological and biochemical characteristics in triazine resistant biotypes of four Amaranthus species. Journal of Plant Physiology. 143: 632-636.
Lipid composition and chloroplast ultrastructure in triazine resistant biotypes of Amaranthus species.
Dominguez, C., M. Tena, I. Rodriguez, R. Prado de, and R. De Prado. 1994. Lipid composition and chloroplast ultrastructure in triazine resistant biotypes of Amaranthus species. Journal of Plant Physiology. 143: 637-642.
Rapid diagnosis of ALS/AHAS-resistant weeds.
Gerwick, B. C., L. C. Mireles, and R. J. Eilers. 1993. Rapid diagnosis of ALS/AHAS-resistant weeds. Weed Technology. 7: 519-524.
Tolerance of cultured Amaranthus retroflexus cells to atrazine.
Shigematsu, Y., S. Chaicharoen, F. Sato, and Y. Yamada. 1993. Tolerance of cultured Amaranthus retroflexus cells to atrazine. Zeitschrift fur Naturforschung. Section C, Biosciences. 48: 275-277.
Triazine resistance in biotypes of Solanum nigrum and four Amaranthus species found in Spain.
Prado, R. de, C. Dominguez, M. Tena, and R. De Prado. 1993. Triazine resistance in biotypes of Solanum nigrum and four Amaranthus species found in Spain. Weed Research. 33: 17-24.
Annual weed populations resistant to atrazine in Aragon.
Lopez, C., C. Lopez, S. Murillo, C. Zaragoza, R. Prado de, and R. De Prado. 1993. Annual weed populations resistant to atrazine in Aragon. Proceedings of the 1993 Congress of the Spanish Weed Science Society, Lugo, Spain, 1-3 December 1993. : 249-253.
The infraspecific structure of weeds in relation to herbicide resistance.
Juttersonke, B. and K. Arlt. 1992. The infraspecific structure of weeds in relation to herbicide resistance. Zeitschrift-fur-Pflanzenkrankheiten-und-Pflanzenschutz. 1992, presented at the 16th German conference on weed biology and control, held at Stuttgart-Hohenheim, Germany, on 10-12 March 1992. 13: 475-481.
Quantitative comparison of chloroplast ultrastructure in mesophyll cells of triazine resistant and triazine sensitive Amaranthus retroflexus L. plants.
Kutik, J. and E. Bergmannova. 1991. Quantitative comparison of chloroplast ultrastructure in mesophyll cells of triazine resistant and triazine sensitive Amaranthus retroflexus L. plants. Biologia Plantarum. 33: 510-512 + .
The problem of triazine resistance in annual weeds in maize and horticultural crops.
Kees, H. and A. Lutz. 1991. The problem of triazine resistance in annual weeds in maize and horticultural crops. Gesunde Pflanzen. 43: 216-220.
Structure-activity relationships of triazinone herbicides on resistant weeds and resistant Chlamydomonas reinhardtii.
Oettmeier, W., U. Hilp, W. Draber, C. Fedtke, and R. R. Schmidt. 1991. Structure-activity relationships of triazinone herbicides on resistant weeds and resistant Chlamydomonas reinhardtii. Pesticide Science. 33: 399-409.
A bioassay to measure the frequency of sulfonylurea resistance in weed populations.
Davis, E. S., P. K. Fay, and R. G. Lym. 1991. A bioassay to measure the frequency of sulfonylurea resistance in weed populations. Proceedings of the Western Society of Weed Science, Seattle, Washington, USA, 12-14 March 1991. 44: 26-27.
Control of triazine-resistant weeds in maize in southwest Poland.
Rola, J. and H. Rola. 1990. Control of triazine-resistant weeds in maize in southwest Poland. Zeitschrift fur Pflanzenkrankheiten und Pflanzenschutz. 1990. 12: 509-514.
Triazine-resistant weeds found in Spain.
De Prado, R., C. Dominguez, M. Tena, R. Prado de, R. Cavalloro (ed.), and G. Noye (ed.). 1989. Triazine-resistant weeds found in Spain. Importance and perspectives on herbicide-resistant weeds. Proceedings of a meeting of the EC Experts' Group, Tollose, Denmark, 15-17 November 1988. 11561: 67-79.
Characterization of a triple (atrazine-pyrazon-pyridate) resistant biotype of common lambsquarters (Chenopodium album L.).
Solymosi, P. and E. Lehoczki. 1989. Characterization of a triple (atrazine-pyrazon-pyridate) resistant biotype of common lambsquarters (Chenopodium album L.). Journal of Plant Physiology. 4: 685-690.
Methods to determine the occurrence of weeds resistant to triazine herbicides in soil.
Zemanek, J. 1989. Methods to determine the occurrence of weeds resistant to triazine herbicides in soil. Sbornuk UVTUZ, Ochrana Rostlin. 25: 151-158.
Herbicide-resistant weeds and search for biocontrol agents in Yugoslavia.
Sovljanski, B., M. Arsenovic, Z. Klokocar Smit, V. Janjic, Z. Ostojic, R. Cavalloro (ed.), and G. Noye (ed.). 1989. Herbicide-resistant weeds and search for biocontrol agents in Yugoslavia. Importance and perspectives on herbicide-resistant weeds. Proceedings of a meeting of the EC Experts' Group, Tollose, Denmark, 15-17 November 1988. 11561: 153-160.
Co-resistance of atrazine-resistant Chenopodium and Amaranthus biotypes to other Photosystem II inhibiting herbicides.
Solymosi, P. and E. Lehoczki. 1989. Co-resistance of atrazine-resistant Chenopodium and Amaranthus biotypes to other Photosystem II inhibiting herbicides. Zeitschrift fur Naturforschung. Section C, Biosciences. 44: 119-127.
Searching for atrazine resistant weed populations in Czechoslovakia.
Chodova, D. 1988. Searching for atrazine resistant weed populations in Czechoslovakia. Fragmenta Herbologica Jugoslavica. 17: 37-43.
Biological, ecological and cultural effects on the development and distribution of redroot pigweed (Amaranthus retroflexus L.).
Bachthaler, G., A. Ullsperger, and H. Kees. 1988. Biological, ecological and cultural effects on the development and distribution of redroot pigweed (Amaranthus retroflexus L.). Nachrichtenblatt des Deutschen Pflanzenschutzdienstes. 40: 161-170.
Problems of herbicide-resistant weeds.
Mikulka, J. and D. Chodova. 1988. Problems of herbicide-resistant weeds. Agrochemia. 28: 207-212.
Inhibition of photosynthesis in intact plants of biotypes resistant or susceptible to atrazine and cross-resistant to other herbicides.
Oorschot, J. L. P. van, P. H. Leeuwen van, J. L. P. Van Oorschot, and P. H. Van Leeuwen. 1988. Inhibition of photosynthesis in intact plants of biotypes resistant or susceptible to atrazine and cross-resistant to other herbicides. Weed Research. 28: 223-230.
Characterization of triazine-resistant biotypes of Amaranthus spp. found in Spain.
Prado, R. de, C. Dominguez, and M. Tena. 1988. Characterization of triazine-resistant biotypes of Amaranthus spp. found in Spain. VIIIe Colloque International sur la Biologie, l'Ecologie et la Systematique des Mauvaises Herbes. 1: 247-256.
Using the Hill reaction to distinguish between atrazine-resistant and sensitive weed biotypes.
Kockova, M., D. Chodova, and J. Mikulka. 1988. Using the Hill reaction to distinguish between atrazine-resistant and sensitive weed biotypes. Agrochemia. 28: 87-90.
The development of triazine-resistant annual weeds in Bavaria and experience with their control.
Kees, H. 1988. The development of triazine-resistant annual weeds in Bavaria and experience with their control. Gesunde Pflanzen. 40: 407-414.
Occurrence of the triazine herbicide resistant populations of pale persicaria (Polygonum lapathifolium).
Mikulka, J., D. Chodova, and M. Kocova. 1988. Occurrence of the triazine herbicide resistant populations of pale persicaria (Polygonum lapathifolium). Sbornik Uvtiz, Ochrana Rostlin. 24: 297-302.
Photosystem II activity and triazine resistance in weeds.
Sinclair, J. and P. MacDonald. 1987. Photosystem II activity and triazine resistance in weeds. Canadian Journal of Botany. 65: 2147-2151.
New cases of co-resistance in weed stands resistant to atrazine.
Solymosi, P. and E. Lehoczki. 1987. New cases of co-resistance in weed stands resistant to atrazine. Novenyvedelem. 23: 439-444.
Emergence and growth rate of Amaranthus retroflexus biotypes sensitive and resistant to atrazine.
Zemanek, J. 1987. Emergence and growth rate of Amaranthus retroflexus biotypes sensitive and resistant to atrazine. Sbornik UVTIZ, Ochrana Rostlin. 23: 305-314.
Effect of herbicides on a resistant Amaranthus retroflexus biotype and on Echinochloa crus-galli.
Zemanek, J. 1987. Effect of herbicides on a resistant Amaranthus retroflexus biotype and on Echinochloa crus-galli. Agrochemia. 27: 367-371.
The effect of herbicides on resistant and sensitive biotypes of pigweed (Amaranthus retroflexus L.).
Zemanek, J. 1986. The effect of herbicides on resistant and sensitive biotypes of pigweed (Amaranthus retroflexus L.). Sbornik UVTIZ, Ochrana Rostlin. 22: 149-157.
Verification of the fluorescence method for determining redroot pigweed biotypes resistant to atrazine.
Chodova, D., J. Kral, and Z. Martinkova. 1986. Verification of the fluorescence method for determining redroot pigweed biotypes resistant to atrazine. Agrochemia. 26: 356-357.
Electrophoretic variation in triazine-resistant and susceptible populations of Amaranthus retroflexus L.
Warwick, S. I. and L. D. Black. 1986. Electrophoretic variation in triazine-resistant and susceptible populations of Amaranthus retroflexus L. New Phytologist. 104: 661-670.
1986 Survey of perennial weeds in Wisconsin.
Doll, J. D. and M. Visocky. 1986. 1986 Survey of perennial weeds in Wisconsin. Proceedings, North Central Weed Control Conference. 41: 64-74.
Detection of atrazine-resistant biotypes of pigweed and goosefoot by the fluorescence method.
Chodova, D., J. Kral, and J. Zemanek. 1986. Detection of atrazine-resistant biotypes of pigweed and goosefoot by the fluorescence method. Agrochemia. 26: 205-207.
Organization of the photosynthetic apparatus from triazine-resistant and -susceptible biotypes of several plant species.
Lemoine, Y., J. P. Dubacq, G. Zabulon, and J. M. Ducruet. 1986. Organization of the photosynthetic apparatus from triazine-resistant and -susceptible biotypes of several plant species. Canadian Journal of Botany. 64: 2999-3007.
Mapping of atrazine resistance for Amaranthus retroflexus L. in Hungary.
Solymosi, P. and S. Kostyal. 1985. Mapping of atrazine resistance for Amaranthus retroflexus L. in Hungary. Weed Research. 25: 411-414.
Aspects of the biology and control of pigweed (Amaranthus spp.) in New York.
Senesac, A. F. 1985. Aspects of the biology and control of pigweed (Amaranthus spp.) in New York. Dissertation Abstracts International, B Sciences and Engineering. 46: 1007.
The occurrence of populations of pigweeds (Amaranthus spp.) resistant to atrazine in Czechoslovakia.
Zemanek, J. and J. Mikulka. 1985. The occurrence of populations of pigweeds (Amaranthus spp.) resistant to atrazine in Czechoslovakia. Sbornik UVTIZ Ochrana Rostlin. 21: 39-46.
An altered concept of the model of the binding sites for triazine in Amaranthus retroflexus L. and Senecio vulgaris L.
Turcsanyi, G. 1984. An altered concept of the model of the binding sites for triazine in Amaranthus retroflexus L. and Senecio vulgaris L. Acta Botanica Hungarica. 30: 201-204.
Effects of inhibitors and diverters of photosynthetic electron transport on herbicide resistant and susceptible weed biotypes.
Fuerst, E. P. 1984. Effects of inhibitors and diverters of photosynthetic electron transport on herbicide resistant and susceptible weed biotypes. Dissertation Abstracts International, B Sciences and Engineering. 45: 1079-1080.
Morphological mutants in populations resistant to atrazine.
Solymosi, P. 1983. Morphological mutants in populations resistant to atrazine. Novenyvedelem. 19: 264.
Characteristics of herbicide binding sites in photosystem 2 in triazine-susceptible and -resistant Amaranthus retroflexus L. biotypes.
Turcsanyi, G. and A. Faludi Daniel. 1983. Characteristics of herbicide binding sites in photosystem 2 in triazine-susceptible and -resistant Amaranthus retroflexus L. biotypes. Photosynthetica. 17: 602-604.
Distribution of triazine-resistant weeds in Hungary and possibilities of control.
Torok, T. 1983. Distribution of triazine-resistant weeds in Hungary and possibilities of control. Novenyvedelem. 19: 263.
Comparative study of atrazine resistant populations of Amaranthus retroflexus from different locations in Hungary.
Solymosi, P. and E. Lehoczki. 1983. Comparative study of atrazine resistant populations of Amaranthus retroflexus from different locations in Hungary. Novenytermeles. 32: 427-435.
Evidence for two different herbicide binding proteins at the reducing side of photosystem II.
Oettmeier, W., K. Masson, C. Fedtke, J. Konze, R. R. Schmidt, J. Miyamoto (ed.), P. C. Kearney (ed.), S. Matsunaka (ed.), D. H. Hutson (ed.), and S. D. Murphy (ed.). 1983. Evidence for two different herbicide binding proteins at the reducing side of photosystem II. Pesticide chemistry: human welfare and the environment. Volume 3. Mode of action, metabolism and toxicology. : 91-96.
Weeds resistant to herbicides.
Voevodin, A. V. 1982. Weeds resistant to herbicides. Sel'skoe Khozyaistvo za Rubezhom. 8: 30-34.

CONTRIBUTING WEED SCIENTISTS

FRANCOIS TARDIF	Edit
Associate Professor University of Guelph Department of Plant Agriculture Guelph, N1G 2W1, Ontario Canada Email Francois Tardif Web : Web Site Link

Acknowledgements

Where to now?

The Herbicide Resistance Action Committee, the Weed Science Society of America, and weed scientists in Ontario have been instrumental in providing you this information. Particular thanks is given to Francois Tardif for providing detailed information.

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