Distribution of Glyphosate and Cloransulam-Methyl Resistant Giant Ragweed (Ambrosia trifida L.) Populations in Southern Ontario
Giant ragweed is a
species of flowering plant in the sunflower family. It is native to North
America, and can also be found in orchards and non-cropped areas such as
ditches and river banks in southern areas of Canada and the Midwestern and
Eastern United States. It is an erect annual broadleaf weed and has a long
emergence period lasting from early March to late July. It also has the ability
to grow rapidly and can reach heights of up to 6 m.
Actually, giant
ragweed is also a very competitive weed in row crop production and has been
found to drastically reduce soybean yield. In 2008, giant ragweed was the first
weed species with confirmed resistance to glyphosate in Canada. As of 2010
there were 48 locations with confirmed glyphosate resistant giant ragweed in
Essex, Kent and Lambton counties. In addition, there was suspected resistance
to cloransulam-methyl.
The objectives of
this research were 1) to conduct an expanded field survey on the distribution
of glyphosate resistant giant ragweed in Ontario, 2) to determine the
distribution of cloransulam-methyl resistant giant ragweed in Ontario, and 3)
to determine the distribution of multiple resistant (glyphosate and
cloransulam-methyl) giant ragweed in Ontario.
In 2011 and 2012
giant ragweed seed was collected from 85 field sites in Essex (16), Kent (34),
Lambton (23), Elgin (3), Middlesex (6), Lennox & Addington (1), Huron (1)
and Brant (1) counties. In total, there were 34 additional locations confirmed
with glyphosate resistant giant ragweed in Ontario. There were 11 locations
confirmed with cloransulam-methyl resistant giant ragweed and 5 locations with
multiple resistance to both glyphosate and cloransulam-methyl.
In summary, this
survey demonstrated that glyphosate resistant giant ragweed was no longer
confined to the southwestern portion of Ontario. Since the initial assessment
of its distribution in Ontario, the presence of glyphosate-resistant giant
ragweed had been confirmed in four additional counties.
Article by Yuji Mitadera, et al, from Japan.
Image by Tim Martin, from Flickr-cc.
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