Submitted to: Weed Technology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/1995
Publication Date: N/A
Interpretive Summary: Foxtail (Setaria spp.) seedling growth models were developed to better predict the time of a successful postemergence weed control treatment, such as a nicosulfuron (Accent) application. Height growth of giant, green, and yellow foxtails was monitored in greenhouse and field settings. In a separate 2-year field study, green foxtail densities and associated corn yield losses were manipulated by applying a single application of nicosulfuron and at specified intervals of growing degree days (GDD). Foxtail height growth was closely related to GDD in both greenhouse and field settings. Neither soil, water, nor rainfall influenced height growth until after about 300 cumulative GDD (centigrade) after planting. Nicosulfuron applications between 200 to 300 GDD after planting minimized corn yield losses due to green foxtail interference. Green foxtail height was about 2" at 200 GDD and 4" at 300 GDD after planting. These heights correspond to the label recommendation for nicosulfuron application for foxtail control in corn. These results indicate that foxtails can be managed effectively by applying nicosulfuron between 200 to 300 GDD after planting, thereby alleviating the need for costly and time-consuming daily scouting of fields to monitor foxtail seedling heights.
Technical Abstract: Seedling growth of giant, green, and yellow foxtail was monitored in greenhouse and field settings and compared with elapsed thermal time (growing degree days, GDD, base 10 C). In addition, green foxtail in corn was controlled with nicosulfuron applied at seven intervals between 100 and 450 GDD after planting in 1993 and 1994. Average height growth in response eto GDD was similar in greenhouse and field settings within each foxtail species, and it was similar between years in the field. Average height growth (mm) of field populations of foxtail seedlings was described as: giant foxtail = (-0.71 + 0.038* GDD)**2, green foxtail = (0.27 + 0.033* GDD)**2, and yellow foxtail = (0.04 + 0.30* GDD)**2. Leaf development was linearly related to GDD. In 1993 corn yield losses due to green foxtail interference were least when nicosulfuron was applied 200 to 300 GDD after planting, at the time green foxtail height was 50 to 100 mm. In 1994 corn yield losses were minimized if nicosulfuron was applied any time before 30 GDD.