Dose response of yellow and white popcorn hybrids to glyphosate, a premix of 2,4‐D choline and glyphosate, or dicamba

Abstract

Popcorn (Zea mays L. var. everta) is difficult to distinguish from field corn (Zea mays L. var. indentata) and is produced adjacent or in close proximity to field corn and soybean [Glycine max (L.) Merr.]. This creates a potential for misapplication or drift of herbicides used in nearby corn and soybean. Field experiments were conducted near Clay Center, Nebraska in 2017 and 2018 to determine the effect of glyphosate, 2,4‐D choline/glyphosate (premix), or dicamba on the growth and yield of popcorn. Treatments included nontreated control and four rates of glyphosate, 2,4‐D choline/glyphosate, or dicamba applied post‐emergence (POST) at five‐ or eight‐leaf (V5 and V8, respectively) popcorn growth stages to white and yellow popcorn hybrids. A three‐parameter log‐logistic model was fitted to treatment combination with varying herbicide rates. Glyphosate and 2,4‐D choline/glyphosate applied at V5 had greater injury, biomass reduction, height reduction, and yield loss than at V8. The two hybrids responded similarly to herbicides at most measurements. At the V8 application, 2,4‐D choline/glyphosate resulted in greater injury in the white hybrid; however, no hybrid differences in glyphosate sensitivity were observed at the V8 growth stage. Glyphosate and 2,4‐D choline/glyphosate at 0.25× rates resulted in complete plant death in both hybrids, whereas the highest dicamba dose (2×) caused 11% injury and no biomass reduction, plant height reduction, or yield loss. These results demonstrate the sensitivity of popcorn to glyphosate, 2,4‐D choline/glyphosate, or dicamba and can be of immediate educational use and practical implementation for popcorn producers, herbicide applicators, and agronomists.

Significance of application timing, formulation, and cytochrome P450 genotypic class on sweet corn response to dicamba

“…Sweet corn sensitivity to dicamba and other CYP-metabolized herbicides also has been shown to vary by growth stage at the time of application. In glyphosate-tolerant popcorn, there was no significant difference in injury, biomass, or plant height between dicamba applied at V5 or V8; however, glyphosate and 2,4-D caused greater injury at V5 than at V8 (Barnes et al 2020). Similar results in sweet corn showed mesotrione and nicosulfuron decreased yield more when applied between V3 and V5 compared with between V5 and V7 (Meyer et al 2010).…”

Genetic diversity of North American popcorn germplasm and the effect of population structure on nicosulfuron response

“…Recent studies have been unable to identify differences in herbicide sensitivity among several (i.e., up to eight entries) commercial white and yellow popcorn hybrids (Barnes, Lawrence, Knezevic, Irmak et al., 2020; Barnes, Lawrence, Knezevic, Rodriguez et al., 2020). However, given the unknown origin of the hybrid parents used in these studies and the prevalence of North American Yellow Pearl Popcorns in commercial germplasm, these hybrids were likely selected using kernel color alone and do not represent the two groups of North American popcorn.…”

Reliable and rapid identification of glyphosate‐resistance in the invasive weed Amaranthus palmeri in China

“…18 One is the greenhouse glyphosate dose-response (GDR) assay. 19 The other is a molecular method based on the glyphosate-resistance mechanism. 20 The greenhouse glyphosate dose-response assay is the more widely used method to identify and quantify herbicide resistance.…”

“…In general, two kinds of methods have been developed to identify a weed's level of herbicide resistance 18 . One is the greenhouse glyphosate dose–response (GDR) assay 19 . The other is a molecular method based on the glyphosate‐resistance mechanism 20 .…”