Weed Technology (2004) 18, 810-815

Clayton D. Myhre, Heather A. Loeppky and F. Craig Stevenson (2004)
MON-37500 for weed control and alfalfa seed production
Weed Technology 18 (3), 810-815
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 0.5x, 1x, and 1.5x label-recommended rates of MON-37500 and also 2,4-DB and hexazinone. MON-37500 applied at the 1x and 1.5x 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 1x and 1.5x 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 1x 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 0.5x MON-37500 rate often resulted in inferior weed control relative to the 1x and 1.5x 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.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website

Research topic(s) for pests/diseases/weeds:
control - general
damage/losses/economics

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Cirsium arvense (weed)	Alfalfa/lucerne (Medicago sativa)	Canada (west)
	Taraxacum officinale (weed)	Alfalfa/lucerne (Medicago sativa)	Canada (west)
	Elymus repens (weed)	Alfalfa/lucerne (Medicago sativa)	Canada (west)