Improving the Management of Dicot Weeds in Peanut with Narrow Row Spacings and Residual Herbicides

Narrow row spacings in peanut (Arachis hypogaea L.) production suppress spotted wilt and promote rapid canopy closure, improving competitiveness with weeds. Trials were conducted from 1999 to 2001 to determine if weed suppression in narrow row spacings, in conjunction with new residual herbicides supplemented with nonresidual herbicides, improved weed control and reduced herbicide use. Within each row spacing were three levels of weed management using the residual herbicides imazapic {(±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1Himidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid}, diclosulam [N-(2,6-dichlorophenyl)-5-ethoxy-7fluoro[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide], sulfentrazone {N-[2,4-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3methyl-5-oxo-1H-1,2,4-triazol-1-yl]phenyl]methanesulfonamide}, and flumioxazin {2-[7-fluoro-3,4-dihydro-3-oxo-4-(2propynyl)-2H-1,4-benzoxazin-6-yl]-4,5,6,7-tetrahydro-1H-iso-indole-1,3(2H)-dione}. Minimal weed management was ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)ben-zenamine] alone for annual grass control. Moderate weed management was ethalfluralin, a residual herbicide, and 2,4-DB [4-(2,4-dichlorophenoxy)butanoic acid]. Intense weed management was the moderate system for each residual herbicide, plus paraquat (1,1ʹ-dimethyl-4,4ʹbipyridinium ion), bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide], and acifluorfen {5-[2chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid}. Peanut seeded in narrow rows had quicker canopy closure than peanut seeded in wide rows. Densities of individual weeds species were not affected, although total weed densities were lower in narrow rows than wide rows. Narrow row spacings with residual herbicides did not reduce herbicide use compared with wide row spacings. Yields were 12% greater in narrow rows than wide rows. While narrow row spacings did not affect individual weed species and reduce herbicide use, narrow row spacings supplement herbicides by reducing the total number of weed escapes.