MON-37500 for Weed Control and Alfalfa Seed Production

Abstract

Alfalfa seed producers have a limited number of herbicide options to manage weed problems. MON-37500 (proposed name sulfosulfuron) is a sulfonylurea herbicide that controls dandelion and quackgrass, two common weeds in alfalfa fields. A study was conducted in two alfalfa fields at Valparaiso and Carrot River, Saskatchewan, Canada, from 1999 to 2001 to evaluate perennial weed control and alfalfa production responses with 0.5×, 1×, and 1.5× label-recommended rates of MON-37500 and also 2,4-DB and hexazinone. MON-37500 applied at the 1× and 1.5× rates at both locations reduced mid-May alfalfa vigor from 100% to between 80 and 90% and increased early-season control of dandelion and quackgrass by about 10 to 40 percentage units, when compared with other herbicide treatments. Improved weed control with 1× and 1.5× MON-37500 rates was sustained into mid-June only at Carrot River and was completely eliminated (100% vigor and 0% weed control), or almost so, by mid-July. MON-37500 did not control Canada thistle. Improved early-season weed control with the 1× MON-37500 rate apparently compensated for the loss of alfalfa vigor at Valparaiso, thus resulting in 27% (57 kg/ha) greater seed yield than with the other herbicide treatments. At Carrot River, hexazinone generally provided levels of weed control similar to MON-37500 but did not injure alfalfa. Consequently, alfalfa yields were highest and the proportion of dead (decaying) seed was least with this treatment. The 0.5× MON-37500 rate often resulted in inferior weed control relative to the 1× and 1.5× rates and never was among the herbicide treatments providing the greatest seed yield. Managing the residual activity of MON-37500 and its negative effect on alfalfa growth, especially at locations with soils having coarse texture and low organic matter content, represents the greatest challenge in making MON-37500 a reliable weed management tool for alfalfa seed producers.

Impact of cultivars and herbicides on weed management in alfalfa

“…Initial injury was usually < 10% when metribuzin, hexazinone, or the low rates of sulfosulfuron and metsulfuron were applied in November or December to dormant alfalfa that was seeded at least 18 mo before herbicide application (i.e., fall of 1998 and 2000 at Creston and fall of 1995 to 2001 at Lethbridge). Myhre et al (2004) also reported that established alfalfa had good tolerance to sulfosulfuron applied in October at locations in northern Saskatchewan.…”

Potential Mutagenicity of Udimo 75 WG Herbicide in Salmonella typhimurium with Ames Test

“…Sulfonylurea herbicides are very strong, highly selective chemicals that are widely used in agriculture and can act at low application rates (Mora et al 2019) and it is estimated that there will be even more sales in the market in further. These herbicides have weak toxicity for animals and humans, and are effective on a broad range of weeds (Myhre et al 2004). Sulfonylurea herbicides inhibit the activity of acetolactate synthase (ALS) enzyme, and the biosynthesis of isoleucine, leucine and valine causing the death of the plant (Jin et al 2012, Delye et al 2018.…”

Application Timing and Degradation Rate of Sulfosulfuron in Soil Co-affect Control Efficacy of Egyptian broomrape (Phelipanche aegyptiaca) in Tomato

“…in different crops, namely acetolactate synthase inhibitors, from the chemical groups sulfonylureas and imidazolinones (Eizenberg et al 2013), and the 5-enolpyruvylshikimate-3-phosphate inhibitor glyphosate (Cochavi et al 2016b). One of the herbicides used for control of P. aegyptiaca in tomatoes is sulfosulfuron, a sulfonylurea herbicide that has been used for selective control of autotrophic weeds in various crops (Eizenberg et al 2003; Geiger and Stahlman 1996; Kutzior et al 1999; Myhre et al 2004). This herbicide is known to have long-term residual activity in neutral and low-alkaline soils, due to its slow degradation rate (Saha and Kulshrestha 2002, 2008), injuring sensitive plants up to 32 mo after its application (Kelley and Peeper 2003; Lyon et al 2003).…”