The Interaction of Acifluorfen and Bentazon in Herbicidal Combinations

Abstract

Acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} and bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were applied singly, in combination at various rates, with and without a crop oil concentrate to common lambsquarters (Chenopodium albumL. # CHEAL), redroot pigweed (Amaranthus retroflexusL. # AMARE), jimsonweed (Datura stramoniumL. # DATST), and velvetleaf (Abutilon theophrastiMedic. # ABUTH) grown in containers in the greenhouse and outdoors. Without crop oil concentrate, synergistic responses to the combinations were measured in common lambsquarters and velvetleaf. Antagonistic responses were measured in jimsonweed. Redroot pigweed response was antagonistic in the greenhouse and synergistic outdoors. The addition of a crop oil concentrate tended to mask the interactions. Crop oil concentrate also increased the droplet size for common lambsquarters, velvetleaf, jimsonweed, and redroot pigweed 53, 41, 28, and 27%, respectively. Neither herbicide at any rate or combination influenced droplet size. Radiolabeled studies showed reduced uptake of14C-acifluorfen when bentazon was present in common lambsquarters and redroot pigweed by 15 and 10%, respectively. Radiolabeled bentazon uptake was reduced 3% in jimsonweed and increased 20% in redroot pigweed when acifluorfen was present.