Previous research has shown that flumioxazin has the potential to cause peanut injury. In response to this concern, laboratory and greenhouse experiments were conducted to investigate the influence of temperature on germination of flumioxazin-treated peanut seed and the effect of interval between flumioxazin application and irrigation on peanut emergence and injury. Laboratory experiments using ¹⁴C-flumioxazin were also conducted to investigate differential tolerance exhibited by peanut, ivyleaf morningglory, and sicklepod to flumioxazin. Flumioxazin treatments containing either water-dispersible granular or wettable powder formulation at 1.4 μmol L⁻¹ did not influence germination compared with nontreated peanut across all temperature regimes (15 to 40 C). Peanut treated with either formulations of flumioxazin preemergence and receiving irrigation at emergence and 2 and 4 d after emergence were injured between 40 and 60%. Peanut treated at 8 and 12 d after emergence were injured between 25 and 15%, respectively. Total ¹⁴C absorbed by ivyleaf mornigglory was 57% of applied whereas sicklepod absorbed 46%, 72 h after treatment (HAT). Peanut absorbed > 74% of applied ¹⁴C 72 HAT. The majority of absorbed ¹⁴C remained in roots of sicklepod, ivyleaf morningglory, and peanut at all harvest times. Ivyleaf morningglory contained 41% of the parent herbicide 72 HAT whereas sicklepod and peanut contained only 24 and 11% parent compound, respectively. Regression slopes indicated slower flumioxazin metabolism by ivyleaf morningglory (a susceptible species) compared with sicklepod and peanut (tolerant species).

Nomenclature: Flumioxazin; ivyleaf morningglory, [Ipomoea hederacea (L.) Jacq.] IPOHE; sicklepod, [Senna obtusifolia (L.) Irwin and Barneby] CASOB; peanut, Arachis hypogaea L. ‘NC 10C’.