Interaction of Seedling Germination, Planting Date, and Flumioxazin on Peanut Physiology under Irrigated Conditions

Diclosulam and flumioxazin applied preemergent (PRE)\r\nresults in direct peanut exposure to these herbicides prior to seedling\r\nemergence. Flumioxazin has been reported to induce injury in adverse weather (i.e. cool-wet soil conditions) at crop\r\nemergence. Research at Ty Ty and Plains, Georgia evaluated the physiological\r\neffects of PRE herbicides to emerging peanut in 2018 and 2019. Peanut seed with\r\nvariable germination and different planting dates were evaluated as additional\r\nfactors. Peanut plant physiological measurements included electron transport\r\n(ETR), net assimilation rate (Anet),\r\nquantum yield of PSII (ΦPSII), and stomatal conductance to water\r\nvapor (GSW). Data were obtained from V3 to R1 peanut growth stages using a\r\nLiCOR 6800, along with stand counts and plant width measures. In 2018,\r\ndiclosulam reduced peanut ETR when measured across multiple growing degree days\r\n(GDD) after planting, compared to the nontreated control (NTC). Flumioxazin\r\nreduced peanut ETR compared to the NTC, at several sample timings for each\r\nplanting date. In 2018 and 2019 at both locations, flumioxazin impacted Anet less than ETR, but was\r\nconsistently similar to/or greater than the NTC. Peanut ΦPSII responded similarly as Anet at each location and yr. GSW was variable in both years; however flumioxazin treated plants had higher GSW\r\nrates than other treated plants. Peanut stand counts, plant widths, and pod\r\nyields noted few differences compared to the physiological measures. Though\r\nsome peanut plant physiological differences were noted when measured at varying\r\nGDD’s after planting with the different PRE treatments, planting date, and seed\r\nvigor, no specific trends were observed. Growers will often observe peanut\r\ninjury from flumioxazin early in the season. However, it is transient and does\r\nnot affect yield.