Response of peanut (Arachis hypogaea L.) to sublethal rates of dicamba plus glyphosate at different growth stages

The widespread adoption of dicamba‐resistant crops has increased the applications of newer dicamba formulations for weed control. However, there is a concern for potential off‐target injury and yield reduction to peanuts (Arachis hypogea L.) planted in close proximity to dicamba‐resistant crops. Field experiments were conducted in the summer of 2019 and 2020 to evaluate peanut response to reduced rates (1/512X, 1/128X, 1/32X, and 1/8X the label rate, 564 + 1280 g ae ha−1) of dicamba plus glyphosate (XtendiMax plus Roundup PowerMax) at 25, 50, and 75 days after planting (DAP) which corresponds to vegetative, flowering, and pod development stages, respectively. Peanut exposure to dicamba plus glyphosate at 25 DAP resulted in 1.6–2.3 times greater injury and 3.4–8.5 times greater height and canopy width reductions compared to 50 and 75 DAP exposures. Peanuts suffered greater yield reduction (18%–19%) when exposed to dicamba plus glyphosate at 25 and 75 DAP than at 50 DAP (10%). Regression analysis indicated a significant linear response for peanut injury (except at 8 weeks after treatment), canopy width reduction, and yield reduction with an increasing rate of dicamba plus glyphosate. Dicamba plus glyphosate at 1/512X rate resulted in a 3% peanut yield reduction, whereas a 41% yield reduction was observed at 1/8X rate. Correlation analysis, with Pearson's rho values ranging from 0.81 to 0.86, showed that peanut injury can be a useful predictor for estimating yield reduction. Therefore, extreme care must be taken to prevent drift occurrence or spray‐tank contamination when applying dicamba plus glyphosate on XtendFlex crops near peanut fields. Core Ideas Dicamba plus glyphosate caused greater injury to peanut at vegetative than at flowering or pod development stages. The yield loss was two times greater at the vegetative and pod development stages than at the flowering stage. The 1/8X label rate of dicamba plus glyphosate reduced peanut yield up to 41% compared to the weed‐free control.