Tips to Maximize Glyphosate Effectiveness
Christy Sprague, MSU Crop and Soil Sciences, wrote an article for the MSU IPM newsletter on maximizing glyphosate activity: http://www.ipmnews.msu.edu/fieldcrop/fieldcrop/tabid/56/articleType/ArticleView/articleId/2706/Tips-for-maximizing-glyphosate-activity.aspx
I’ve taken a few tips verbatim from that article:
- Ammonium sulfate (AMS) should always be added to all glyphosate products. We recommend adding dry spray grade AMS at 17 lbs/100 gal. or the equivalent of 17 lbs/100 gal. of liquid AMS products. The addition of AMS minimizes the negative effect of hard water on glyphosate activity and is important for velvetleaf control, regardless of water quality.
- Applying the appropriate glyphosate rate in glyphosate-resistant crops is important for consistent weed control. Proper glyphosate rates should be based on weed type, weed size and spray volume. In most cases, the appropriate rate to use for weed control in glyphosate-resistant crops is 0.75 lbs a.e./A of glyphosate. This rate will effectively control several annual weed species between two to eight inches tall. However, if weeds become larger or if harder to control species such as common lambsquarters or giant ragweed are present, increase the glyphosate rate to 1.13 lbs a.e./A to adequately control these weed species.
- It is important to make timely glyphosate applications to minimize the chances of yield loss due to early-season weed competition and to maximize weed control. The optimum time for glyphosate applications in corn is before weeds are four inches tall, and when weeds are four inches tall in narrow-row (7.5 and 15 inches) soybeans and six inches tall in wide-row (30 inches) soybeans. Controlling weeds at these times reduces the chances for yield loss, as well as reduces the risk of weed control failures of larger weed that may be under stressful conditions (drought, stem-boring insects, coverage issue, etc.).
Full podcast here: Maximizing Glyphosate Effectiveness