Growth and Yield Response of Peanut to Simulated Drift of Glufosinate at Vegetative and Reproductive Growth Stages

Abstract The increased incidence of glyphosate-resistant weeds has led to an exponential increase in the use of glufosinate in glufosinate-resistant corn, cotton, and soybean. Field experiments were conducted in 2021 and 2022 to evaluate peanut response to glufosinate at 25 and 60 d after planting, corresponding to vegetative (V3) and reproductive (R4) growth stages, at 1.2, 4.7, 18.9, 75.5, and 302 g ai ha -1 representing 1/514 to 1/2 of the labeled rate of 604 g ha -1 . Peanut injury and canopy and yield reductions from glufosinate were <10% when applied at 1.2, 4.7, and 18.9 g ha -1 . However, at 75.5 and 302 g ha -1 peanut injury ranged from 24% to 72% for V3 exposure timing and 33% to 54% for R4 exposure timing. Similarly, glufosinate at 75.5 and 302 g ha -1 reduced peanut canopy width by 10% to 23% for V3 exposure timing and 43% to 57% for R4 exposure timing. Averaged across exposure timing, peanut yield was reduced by 15% and 61% at 75.5 and 302 g ha -1 , respectively. Averaged across rates, peanut yield reduction was 18% for V3 exposure timing, with glufosinate at 298 g ha -1 required to cause an estimated 50% reduction in yield. For R3 exposure timing, peanut yield reduction was 20%, with glufosinate at 243 g ha -1 required to cause an estimated 50% reduction in yield. There was no difference in Normalized Difference Vegetative Index (NDVI) between untreated plants and peanut exposed to glufosinate at 1.2, 4.7, and 18.9 g ha -1 . However, peanut exposed to glufosinate at 75.5 and 302 g ha -1 were distinguished from untreated plants with lower NDVI values. Based on Pearson’s Rho correlation coefficient, the best timing for assessing potential yield reduction based on injury was between 2 and 4 wk after treatment.