TITLE:
Glyphosate-Resistant Giant Ragweed (Ambrosia trifida L.): 2,4-D Dose Response and Control with Postemergence Herbicides in Soybean
AUTHORS:
Joanna Follings, Nader Soltani, Darren E. Robinson, François J. Tardif, Mark B. Lawton, Peter H. Sikkema
KEYWORDS:
Glyphosate Resistance; Multiple Herbicide-Resistant Crops; Preplant Herbicides; Postemergence Herbicides
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.4 No.9,
August
29,
2013
ABSTRACT: Glyphosate
resistant giant ragweed is an increasing problem in glyphosate resistant
cropping systems in southwestern Ontario. The postemergence herbicides
registered for use in soybean in Ontario do not provide consistent control of
glyphosate resistant giant ragweed. There is limited research on the lowest
effective rate of 2,4-D for the control of glyphosate resistant giant ragweed.
Consequently, the objectives of this study were a) to determine the efficacy of
herbicides applied postemergence for the control of glyphosate resistant
giant ragweed in glyphosate resistant soybean, and b) to determine the lowest
effective rate of 2,4-D for the control of glyphosate-resistant giant ragweed.
Ten postemergence herbicide combinations and seven rates of 2,4-D
were evaluated in field studies conducted in 2011 and 2012 at six locations
confirmed with glyphosate-resistant giant ragweed. The post emergence
herbicides evaluated did not provide acceptable/consistent control.
Of the herbicides evaluated, glyphosate plus cloransulam-methyl provided 26% to
70% control 8 WAA of glyphosate resistant giant ragweed, which was the best of
the herbicides combinations evaluated. The doses of 2,4-D required to reduce
giant ragweed shoot dry weight by 50, 80 and 95% were 142, 310 and 1048 g a.e. ha-1,
respectively.