| Aminopyralid is a synthetic auxin herbicide of the pyridinecarboxylic acid family that was introduced in 2005; thus, the amount of information available on this herbicide is limited. Greenhouse experiments were conducted to determine the absorption, translocation, and metabolism of 14C-aminopyralid in the southern forage bahiagrass (Paspalum notatum Fluegge). Absorption of 14C-aminopyralid was 99% at 4 DAT with 89% of the 14C recovered remaining in the treated leaves. Shoots of plants contained 9% of recovered 14C, and less than 1.0% of recovered 14C was translocated to the roots of bahiagrass plants. The portion of recovered 14C that remained in the form of aminopyralid was 94% or greater. Due to the environmental persistence of this herbicide, field experiments were conducted to determine the sensitivity of bell pepper, Capsicum annuum L.; eggplant, Solanum melongena L.; muskmelon, Cucumis melo L.; tomato, Lycopersicon esculentum Mill.; watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai to aminopyralid soil residiues. Aminopyralid was applied at six rates from 0.0014 kg ae ha-1 to 0.0448 kg ae ha-1, and vegetable crops were planted in the treated areas. At an aminopyralid soil concentration of 0.2 mug kg-1, the limit of quantitation (LOQ) for aminopyralid in this research, crop injury ratings 6 wk after planting were 48 (bell pepper), 67 (eggplant), 71 (tomato), 3 (muskmelon), and 3% (watermelon), and fruit yield losses (relative to the untreated control) at 0.2 mug kg-1 aminopyralid were 61, 64, 95, 8, and 14% in those respective crops. Laboratory experiments were conducted to determine the sorption of aminopyralid to soil and clay minerals. Freundlich distribution coefficients (Kf) for aminopyralid ranged from 0.35 in a Cecil sandy loam to 0.96 in an Arredondo fine sand. It was concluded that soil sorption of aminopyralid was greater than that of picloram and that the potential for off-target movement of aminopyralid is less than that of picloram. Mineralization of picloram and aminopyralid in Sharkey clay was 15.2 and 23.7%, respectively, and mineralization of those respective herbicides in Arredondo fine sand was 5.4 and 9.2%. |
