Evaluating Postemergence Herbicides for Relative Corn Safety

Abstract

When determining the need for a postemergence herbicide, growers consider many factors including yield loss due to competition from existing weeds, effectiveness of various herbicide options, timing of application, as well as crop safety. Few trials have been conducted that compare corn injury and yield loss due to various active ingredients. Injury and potential yield loss from various postemergence herbicides were evaluated under weed‐free conditions. At labeled use rates, chlorosis and stunting were generally at acceptable levels (> 11%) and did not impact yield. In separate experiments with twice the labeled use rate, stunting was the most pronounced symptom and lasted longer than twisting or chlorosis. Yield was reduced with foramsulfuron, foramsulfuron plus iodosulfuron, primisulfuron plus dicamba, and dicamba plus atrazine compared to the untreated control. Predicting yield loss based on visual symptoms was not reliable. In addition, corn responded differently to various herbicide mixtures containing similar active ingredients. Knowledge of herbicides that have a higher risk of injury will allow farmers to make more informed decisions on postemergence herbicides, particularly when conditions are favorable for corn injury.

Tolerance of Maize (<i>Zea mays</i> L.) and Soybean [<i>Glycine max</i> (L.) Merr.] to Late Applications of Postemergence Herbicides

“…The height of maize plants treated with a single application of dicamba/diflufenzopyr was similar to the untreated control, whereas sequential applications caused an 8% reduction in height 28 DAT ( Table 3). This is similar to other studies which demonstrated stunting or reduced growth in maize due to applications of foramsulfuron or dicamba/diflufenzopyr [10] [12]- [14]. Nevertheless, the observed reductions in height in this study were transient as no differences were detected among the treated and non-treated maize by 56 DAT.…”

“…Nevertheless, the observed reductions in height in this study were transient as no differences were detected among the treated and non-treated maize by 56 DAT. Furthermore, the excellent tolerance to the herbicides used in this study was confirmed as the final maize yields were similar to the untreated control across all treatments (Table 3), consistent with other studies [10] [16] [19].…”

“…Similar levels of injury to maize by foramsulfuron [12]- [15] and dicamba/diflufenzopyr [16]- [19] have been reported. Conversely, up to 16% injury 3 DAT has been found in maize treated with twice the labeled dose of foramsulfuron and 23% injury 7 DAT for maize treated with twice the dose of dicamba/diflufenzopyr [10]. Maize tolerance to foramsulfuron can vary considerably by application timing and maize hybrid [20] [21].…”

“…The exception to this is maize, which can tolerate over two-fold of the maximum labeled dose of glyphosate applied at the 10-leaf stage with minimal injury and little to no yield loss [9]. Furthermore, to the best of our knowledge, few studies have been conducted in the absence of confounding weed competition effects that examine both a range of herbicides comparing relative crop tolerance [10] and the tolerance of crops to a late POST herbicide application [11]. Therefore, the objective of this research was to determine the tolerance of maize and soybean to a late application of select POST herbicides in the absence of weed interference.…”

Effect of Bentonite and Barley Straw on the Restoration of the Biological Quality of Agriculture Soil Contaminated with the Herbicide Successor T 550 SE

“…When selecting a herbicide, many different factors should be taken into account, such as date of application, crop safety, loss of yield due to the competition of already existing weeds and the effectiveness of a given herbicide when applied in combination with another preparation. According to VanGessel et al [76], the maize yield decreased following the application of foramsulfuron, foramsulfuron, and iodosulfuron, primisulfuron and dicamba, as well as dicamba and atrazine. They also observed that the application of a mixture of herbicides with similar active substances caused a varied response.…”