Herbicide Resistant Weeds

GROUP G/9 RESISTANT GIANT RAGWEED (Ambrosia trifida)
Canada: Ontario

Thursday, September 09, 2010

What's on this page

Giant Ragweed

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

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Introduction

Level of Infestation

Giant Ragweed (Ambrosia trifida) is a dicot weed in the Asteraceae family. In Ontario this weed first evolved resistance to Group G/9 herbicides in 2008 and infests soybean. Group G/9 herbicides are known as Glycines (Inhibition of EPSP synthase). Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group G/9 herbicides.

Local weed scientists estimate that Group G/9 resistant Giant Ragweed in Ontario infests 6-10 sites and the number of sites are increasing. They also estimate that there are 51-100 acres infested with Group G/9 resistant Giant Ragweed and the area infested is increasing.

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 Mar 31, 2010 )
Common Name	Giant Ragweed
Species	Ambrosia trifida
Group	Glycines (G/9)
Herbicides	glyphosate
Location	Canada, Ontario
Year	2008
Situation(s)	soybean
Sites	6-10
Acres Infested	51-100
Contributors	Francois Tardif
Input Data	Edit this Case \| Add New Case of Resistance \| Add Note

ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Giant Ragweed biotype with this Giant Ragweed 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 G/9 resistant Giant Ragweed indicate that inheritance is determined by a , 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

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 G/9 resistant Giant Ragweed from Ontario please update the database.

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HERBICIDE RESISTANT GIANT RAGWEED GLOBALLY
#	Country	Year	Sites	Acres	Mode of Action
1.	Canada (Ontario)	2008	6-10	51-100	Glycines (G/9)
2.	USA (Indiana)	1998	unknown	unknown	ALS inhibitors (B/2)
3.	USA (Indiana)	1998	unknown	unknown	ALS inhibitors (B/2)
4.	USA (Illinois)	1998	unknown	unknown	ALS inhibitors (B/2)
5.	USA (Ohio)	1998	101-500	1001-10000	ALS inhibitors (B/2)
6.	USA (Iowa)	2000	11-50	101-500	ALS inhibitors (B/2)
7.	USA (Ohio)	2004	2-5	101-500	Glycines (G/9)
8.	USA (Indiana)	2005	1	11-50	Glycines (G/9)
9.	USA (Arkansas)	2005	6-10	101-500	Glycines (G/9)
10.	USA (Kansas)	2006	2-5	501-1000	Glycines (G/9)
11.	USA (Minnesota)	2006	2-5	101-500	Glycines (G/9)
12.	USA (Ohio) Multiple Resistance	2006	1	101-500	ALS inhibitors (B/2) Glycines (G/9)
13.	USA (Tennessee)	2007	101-500	1001-10000	Glycines (G/9)
14.	USA (Iowa)	2009	6-10	unknown	Glycines (G/9)
15.	USA (Missouri)	2009	2-5	101-500	Glycines (G/9)

FACT SHEETS AND OTHER LITERATURE	Format
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Scientific Abstracts on Herbicide Resistant Ambrosia trifida
Evolved resistance to acetolactate synthase–inhibiting herbicides in common sunflower (Helianthus annuus), giant ragweed (Ambrosia trifida), and shattercane (Sorghum bicolor) in Iowa
Ian A. Zelaya, and Micheal D. K. Owen 2004. Evolved resistance to acetolactate synthase–inhibiting herbicides in common sunflower (Helianthus annuus), giant ragweed (Ambrosia trifida), and shattercane (Sorghum bicolor) in Iowa Weed Science. 52: 538-548.
Absorption, translocation, and metabolism of imazethapyr in common ragweed (Ambrosia artemisiifolia) and giant ragweed (Ambrosia trifida).
Ballard, T. O., M. E. Foley, and T. T. Bauman. 1995. Absorption, translocation, and metabolism of imazethapyr in common ragweed (Ambrosia artemisiifolia) and giant ragweed (Ambrosia trifida). Weed Science. 43: 572-577.

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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