Vertical mobility and cotton tolerance to trifludimoxazin, a new protoporphyrinogen oxidase-inhibiting herbicide, in three West Texas soils

Trifludimoxazin, a new protoporphyrinogen oxidase–inhibiting herbicide, is being evaluated for possible use as a soil-residual active herbicide treatment in cotton for control of small-seeded annual broadleaf weeds. Laboratory and greenhouse studies were conducted to compare vertical mobility and cotton tolerance of trifludimoxazin to flumioxazin and saflufenacil, which are two currently registered protoporphyrinogen oxidase–inhibiting herbicides for use in cotton, in three West Texas soils. Vertical soil mobility of trifludimoxazin was similar to flumioxazin in Acuff loam and Olton loam soils, but was more mobile than flumioxazin in the Amarillo loamy sand soil. The depth of trifludimoxazin movement after a 2.5-cm irrigation event ranged from 2.5 to 5.0 cm in all soils, which would not allow for crop selectivity based on herbicide placement, because ideal cotton seeding depth is from 0.6 to 2.54 cm deep. Greenhouse studies indicated that PRE treatments were more injurious than the 14 d preplant treatment when summarized across soils for the three herbicides (43% and 14% injury, respectively). No differences in visual cotton response or dry weight was observed after trifludimoxazin preplant as compared with the nontreated control within each of the three West Texas soils and was similar to the flumioxazin preplant across soils. On the basis of these results, a use pattern for trifludimoxazin in cotton may be established with the use of a more than 14-d preplant restriction before cotton planting.

Soil Mobility of Allyl Isothiocyanate and Chloropicrin as Influenced by Surfactants and Soil Texture

Methyl bromide (MeBr) was identified as a stratospheric ozone depletory; therefore, the use of MeBr was phased out in the United States in 2005. Chloropicrin (CP) and allyl isothiocyanate (AITC) are MeBr replacements. A mixture of CP and AITC is commonly applied to broaden the pest control spectrum. These two fumigants have low soil mobility; however, their efficacy could be improved if their soil mobility were enhanced. This research was conducted to study the effects of surfactants applied at 5% (v/v) for CP mobility and AITC mobility in soils. Mobility of the CP/AITC mixture applied with a nonionic surfactant comprising oleic, linoleic, and palmitic acids (nonionic-1) and mobility of the CP/AITC mixture applied with a nonionic surfactant comprising C9 hydrocarbon aromatics and calcium alkylarylsuphonate (nonionic-2) were compared with mobility of the CP/AITC mixture applied without surfactants in three soils (Elder sandy loam, Chualar loam, and Blanco clay loam) during a laboratory study. Nonionic-1 surfactant increased the concentration of total leachate collected for AITC by five and CP by 11 compared with CP/AITC applied alone. Surfactants may influence the fumigant mobility in soil by affecting the sorption/desorption equilibrium. Our research suggested that increased AITC mobility and CP mobility in soil with the addition of adding nonionic-1 surfactant may be due to the adsorption behavior of the surfactant in the soil and the solubilizing capability of the surfactant with pesticides.