Absorption and Translocation of Aminocyclopyrachlor and Aminocyclopyrachlor-Methyl Ester in Canada Thistle (Cirsium arvense)

Abstract

Laboratory studies were conducted using 14 C-aminocyclopyrachlor (DPX-MAT28) and its 14 C-methyl ester formulation (DPX-KJM44) to (1) determine the adjuvants' effects on absorption, (2) compare the absorption and translocation of aminocyclopyrachlor free acid with the methyl ester, and (3) determine the rate at which aminocyclopyrachlor-methyl ester is metabolized to the free acid in Canada thistle. Canada thistle plants were grown from root cuttings and treated in the rosette growth stage. The effect of different adjuvants on absorption was determined by treating individual leaves with formulated herbicide plus 14 C-herbicide alone or with methylated seed oil (MSO), crop oil concentrate, or nonionic surfactant with and without urea ammonium nitrate and ammonium sulfate. Plants were harvested 96 h after treatment (HAT). For absorption and translocation experiments, plants were oversprayed with aminocyclopyrachlor or its methyl ester at a rate of 0.14 kg ae ha 21 in combination with 1% MSO. Formulated herbicide plus 14 C-herbicide was then applied to a protected leaf, and plants were harvested 24 to 192 HAT. Plants were harvested and radioactivity was determined in the treated leaf and in aboveground and belowground tissues. Metabolism of aminocyclopyrachlor-methyl ester to the free acid was determined 2, 6, and 24 HAT. All aboveground biomass was analyzed by high-performance liquid chromatography to establish the ratio of methyl ester to free acid. MSO applied with either herbicide formulation resulted in the highest absorption compared with no surfactant. Significantly greater aminocyclopyrachlor-methyl ester was absorbed, compared with the free acid, which was reflected in the greater aboveground translocation for the methyl ester. Both formulations had similar amounts of translocation to the roots, with 8.6% (SE 6 3.3) for the methyl ester compared with 6.2% (SE 6 2.5) for the free acid. Approximately 80% of the methyl ester was converted to the free acid at 6 HAT. Based on this conversion rate, aminocyclopyrachlor translocated as the free acid in Canada thistle. Nomenclature: Aminocyclopyrachlor

Aminocyclopyrachlor Absorption, Translocation and Metabolism in Field Bindweed (Convolvulus arvensis)

“…Aminocyclopyrachlor exhibited slightly lower maximum absorption in field bindweed compared with Canada thistle (57%) (Bukun et al 2010) and rush skeletonweed (64%) (Bell et al 2011). In prickly lettuce and yellow starthistle, aminocyclopyrachlor absorption was much less compared to field bindweed with 5% and 10%, respectively (Bell et al 2011).…”

“…Aminocyclopyrachlor absorption, translocation, and metabolism has been studied in Canada thistle [Cirsium arvense (L.) Scop.] (Bukun et al 2010), as well as prickly lettuce (Latuca serriola L.), rush skeletonweed (Chondrilla juncea L.), and yellow starthistle (Centaurea solstialis L.) (Bell et al 2011).…”

Sorption−Desorption of Aminocyclopyrachlor in Selected Brazilian Soils

“…4 Approximately 80% of the methyl ester is converted to the free acid into plants six hours after leaf absorption. 3 Aminocyclopyrachlor has been developed for noncrop uses such as bare ground, brush, right-of-way, and turf, as well as for range, pasture and invasive weed control 5 and has both foliar and soil activity on susceptible species. 6 It is active on a number of glyphosate and ALS-resistant weeds such as marestail, 7 Russian thistle, kochia, and prickly lettuce.…”

In memoriam Professor Corwin Hansch: birth pangs of QSAR before 1961

“…Discovery researches of the synthetic growth hormone for agricultural use as selective herbicides have been still going on, the most recently launched herbicide-active compound being a tri-substituted pyrimidine carboxylic acid named aminocyclopyrachlor (Fig. 10) from DuPont in 2010 [55].…”