Occurrence and distribution of glyphosate-resistant giant ragweed (Ambrosia trifida L.) in southwestern Ontario

Abstract

Vink, J. P., Soltani, N., Robinson, D. E., Tardif, F. J., Lawton, M. B. and Sikkema, P. H. 2012. Occurrence and distribution of glyphosate-resistant giant ragweed ( Ambrosia trifida L.) in southwestern Ontario. Can. J. Plant Sci. 92: 533–539. Giant ragweed is the first confirmed glyphosate-resistant (GR) weed in Canada. A survey was conducted to document the distribution of GR giant ragweed in southwestern Ontario. Giant ragweed seed was collected from 102 sites in Essex (70), Chatham-Kent (21), Lambton (10) and Waterloo counties (1) during the autumn of 2009 and 2010 prior to soybean harvest. Plants were grown in a growth room, sprayed with glyphosate at 1800 g a.e. ha−1 and classified as resistant or susceptible. GR giant ragweed has been confirmed at 47 new locations in three counties (Essex, Chatham-Kent and Lambton). The results from this survey indicate that GR giant ragweed biotypes occur across a greater area in southwestern Ontario than originally thought. This survey provides an important baseline for future surveys in the province.

Preplant and Postemergence Control of Glyphosate-Resistant Giant Ragweed in Corn

“…Subsequently, resistance to glyphosate was confirmed at 3 and 12 times the maximum recommended rate under greenhouse and field testing, respectively. In 2009 and 2010, a survey of southwestern Ontario confirmed GR giant ragweed populations in 47 additional locations indicating a greater distribution of resistant plants than originally anticipated [10]. By 2012, GR giant ragweed was further detected in four Ontario counties, with five populations demonstrating multiple resistances to both glyphosate and cloransulam-methyl [11].…”

“…Giant ragweed populations were confirmed as resistant to glyphosate prior to study establishment [10]. The first set of trials determined GR giant ragweed control using various PP tank-mixtures while the second examined GR giant ragweed control using POST tank-mixes.…”

Glyphosate-Resistant Giant Ragweed (<i>Ambrosia trifida</i> L.): 2,4-D Dose Response and Control with Postemergence Herbicides in Soybean

“…Giant ragweed seedlings begin to emerge in early March [10] and continue to emerge until late July [11]. Historically, growers in Ontario would control this problematic weed with glyphosate; however, in 2008 giant ragweed was confirmed to be resistant to glyphosate [12].…”

Growth Stage Affects Dose Response of Selected Glyphosate-Resistant Weeds to Premix of 2,4-D Choline and Glyphosate (Enlist Duo™ Herbicide*)

“…Dose response curve indicated ≥ 90% control of 10-cm tall giant ragweed even with a lower than the recommended rate (1,640 g ae ha -1 ) at 21DAT (Figure 2A), while the 20-cm tall giant ragweed was controlled 87 to 93% at the recommended rate at 21 DAT. Similarly, Vink et al (2012) reported > 90% control of 2-to 17-cm tall giant ragweed with 2,4-D ester (500 g ae ha -1 ) applied alone, indicating the sensitivity of giant ragweed to 2,4-D. Higher level of giant ragweed control has been reported in a previous study despite the plant height being higher than recommended. For example, Robinson et al (2012) reported ≥ 99% control of 26-to 46-cm tall giant ragweed with 2,4-D (280 g ae ha -1 ) applied alone or tank-mixed with glyphosate (1,120 g ae ha -1 ).…”

“…Results of this study suggested that Enlist Duo™ herbicide is very effective for controlling glyphosate-resistant giant ragweed. This might be due to giant ragweed's sensitivity to phenoxy herbicides Vink et al, 2012). Recently, Kaur et al (2014) and Jhala et al (2014a) reported 99% control of glyphosate-resistant giant ragweed in Nebraska with herbicide programs that included preplant application of 2,4-D in soybean.…”