Effects of Low-Dose Flumioxazin and Metribuzin Postemergence Applications on Soybean

Abstract

All herbicides will move off-target to sensitive crops when not applied correctly. Therefore, low-dose applications of flumioxazin and metribuzin were evaluated in soybean at the unifoliate, V2, and V4 growth stages. Rates evaluated were 12.5%, 25%, and 50% of the labeled use rates of 72 and 316 g ai ha−1 of flumioxazin and metribuzin, respectively. Flumioxazin injury was characterized by necrosis and visible height and width reduction. Injury increased with rate 3 d after treatment (DAT), with unifoliate, V2, and V4 soybean injured 15% to 30%, 18% to 27%, and 5% to 8%, respectively. Unifoliate and V4 soybean were injured more than V4 soybean 3 to 14 DAT, but injury decreased to <5% by 42 DAT. Soybean yields in the flumioxazin study were 92% to 96% of the nontreated, resulting in a yield loss of 196 to 393 kg ha−1 and a revenue loss of 71 to 141 US$ ha−1. Metribuzin injury was primarily chlorosis with necrosis and a visible reduction in soybean height and width. Soybean at the V2 growth stage was injured 14% more than V4 soybean 3 DAT, regardless of metribuzin rate. Injury to V2 and V4 soybean was similar 14 DAT, with injury of 21% to 40% across rates. Soybean injury when treated at the V2 and V4 growth stages was 6% to 29% 42 DAT compared to unifoliate soybean at 0 to 17%. Soybean yields in the metribuzin study yields were 96% to 98% of the nontreated. However, a 2% to 4% reduction equates to a loss of 90 to 180 kg ha−1 and a revenue loss of 32 to 65 US$ ha−1. Unifoliate and V2 soybean are more sensitive to a low dose of flumioxazin POST, and V2 and V4 soybean are more sensitive to a low dose of metribuzin POST. Injury and the impact on soybean growth could potentially cause economic loss for a soybean producer.

Evaluation of Bentazone Reaction by Growth Stage and Bentazone Dose Across Soybean Genotypes

“…Other researchers also reported that higher doses produced more leaf injury when soybean plants were treated with dicamba and metribuzin (McCown et al 2018;Stephenson et al 2018). The influence of genotypes on the injury was also significant because tolerant accessions produce significantly less necrosis than sensitive accessions.…”

HPPD inhibitor-susceptible soybean growth, yield, and economic return following isoxaflutole and mesotrione applied postemergence

“…Therefore, a reduction in height following the V2 application is what led to greater observed injury. Similarly, Stephenson et al (2019b) reported that metribuzin postemergence at 39.5 and 79 g ai ha −1 , which is 12.5% and 25% of the field use rate, injured V2 soybean greater than unifoliate and V4 soybean at 14, 28, and 42 DAT. Also, fomesafen postemergence at 12.5% of the labeled use rate injured V5 and V7 corn greater than V1, V3, or V9 corn (Sperry et al 2019).…”

“…At all locations, treatments were applied with a CO 2 -pressurized backpack sprayer in a constant carrier volume of 140 L ha −1 . Others have simulated off-target movement of herbicides utilizing constant carrier volume (Al-Khatib et al 2003;Bailey and Kapusta 1993;Ellis et al 2003;Sperry et al 2019;Stephenson et al 2019aStephenson et al , 2019bSteppig et al 2018). At Alexandria, all treatments were applied at 190 kPa using four flat-fan 11002 nozzles (AIXR TeeJet®, TeeJet Technologies Southeast, P.O.…”

“…Visible chlorosis, necrosis, and height reduction were accounted for in the visible injury rating, which is consistent with Frans et al (1986), who described using visible discoloration and stunting to determine visible injury. Soybean heights were recorded at 14, 28, and 42 DAT by measuring 10 randomly selected plants in each plot from the soil to the apical terminal of each plant (Rana et al 2014;Sperry et al 2019;Stephenson et al 2019aStephenson et al , 2019b. Soybean heights were collected to provide a quantitative measurement of potential height reduction caused by the treatments.…”

“…Off-target movement of pesticides ranges from 1% to 8% and 20% to 35% for ground and aerial applications, respectively (Maybank et al 1978;Wolf et al 1992). Others have evaluated simulated herbicide off-target movement on corn (Zea mays L.), cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L.) Moench], rice (Oryza sativa L.), and soybean (Al-Khatib et al 2003;Bailey and Kapusta 1993;Ellis et al , 2003Matocha and Jones 2015;Sperry et al 2019;Stephenson et al 2019aStephenson et al , 2019bSteppig et al 2018).…”