It was reported in the July 20 ICM newsletter (pages 146-147) that there were several incidents where weeds were not controlled by Roundup Ultra. Mention was made of a specific field near Everly, Iowa, where common waterhemp was surviving 3 applications of Roundup Ultra. This field was revisited and most of the common waterhemp plants have succumbed to the third application of 48 ounces of Roundup Ultra. The early applications included a 24-ounce treatment followed by a 36-ounce retreatment. Some plants that were collected from the site and transplanted in the greenhouse have survived all three applications, albeit with considerable damage. Our research efforts to elucidate the reason(s) for these control problems are underway.
Iowa State University
Owen, Micheal D., "Waterhemp update" (1998). Integrated Crop Management News. 2310.
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