Comparison of Glyphosate Formulations for Weed Control and Tolerance in Maize (<i>Zea mays</i> L.) and Soybean [<i>Glycine max</i> (L.) Merr.]

Abstract

Twenty-two field experiments (six maize (Zea mays L.) and five soybean [Glycine max (L.) Merr.] using low glyphosate doses to assess weed control and six maize and five soybean using high glyphosate doses to assess tolerance) were conducted from 2010 to 2012 at two locations in southern Ontario, Canada to compare the commercially available glyphosate formulations of Roundup Weather MAX ® , Clearout ® 41 Plus, and Wise Up ® (WeatherMAX, Clearout, and WiseUp, respectively). In maize and soybean, control of velvetleaf, pigweed species, common lambsquarters, and green foxtail 4 weeks after treatment (WAT) using 900 g·ae·ha −1 ranged from at least 85% to 99%, regardless of formulation. By 8 WAT with 900 g·ae·ha −1 , control of these weeds generally declined, but still ranged from 82% to 97% across all formulations. At harvest, maize yields were similar to the weed-free control for 900 g·ae·ha −1 of glyphosate as WeatherMAX and Clearout; however, reduced weed control with WiseUp resulted in an 8.8% yield loss. For soybean, yields were similar to the weed-free control, regardless of formulation or dose. In the tolerance experiments, 2.1% and 2.8% injury was observed 4 WAT for maize treated with 3600 g·ae·ha −1 of glyphosate as WeatherMAX and WiseUp, respectively. However, maize yields were unaffected by glyphosate formulation or dose. In soybean, visible injury of 8.5%, 4.5%, and 3.7% was observed 1 WAT with 5400 g·ae·ha −1 of glyphosate as WeatherMAX, WiseUp, and Clearout, respectively; by 8 WAT, visible injury was similar to the untreated control, regardless of formulation or dose. The early injury from 5400 g·ae·ha −1 of glyphosate resulted in 8.5%, 4.6%, and 5.5% yield loss for the WeatherMAX, WiseUp, and Clearout formulations, respectively.

Product concentration and usage: Behavioral effects in the glyphosate market

“…The "generic" dummy controls for the possibility that farmers perceive generic products as less effective and therefore compensate by increasing application rates. Although peer-reviewed studies find no significant differences in efficacy between generic and non-generic products (Hartzler, Pringnitz, and Resfell, 2002;Mahoney, Shropshire, and Sikkema, 2014), anecdotal evidence via web-based forums suggests that some farmers are wary of generic products, particularly those not produced in the United States. 7 As noted, previous work has shown that some individuals are willing to purchase non-generic medications at a price premium, despite having the same ingredients.…”

Effect of glyphosate management, formulations and rates on the agronomic performance of maize with the cp4epsps gene

“…adjuvants or salts), each glyphosate formulation is expected to infl uence the rate of uptake and translocation directly, and consequently, the activity of the herbicide (REIS et al, 2014). In this respect, while some reports showed that at least one glyphosate formulation was involved in the occurrence of undesirable eff ects in RR soybean, particularly visible damage (MAHONEY et al, 2014), other studies revealed that the type of glyphosate formulation was unrelated to the occurrence of adverse any eff ects in the crop (ALBRECHT et al, 2018) or in RR2 maize (MAHONEY et al, 2014). For these studies, damage was more related to increases in the rate of glyphosate than the type of formulation.…”