Distribution of Arable Weed Populations along Eastern Arkansas–Mississippi Delta Roadsides: Factors Affecting Weed Occurrence

Abstract

The occurrence of 36 arable weed species across 13 counties in the eastern Arkansas–Mississippi Delta area on 489 randomly selected road sites was surveyed in 2012. Palmer amaranth, johnsongrass, large crabgrass, barnyardgrass, prickly sida, and broadleaf signalgrass were the top six weed species, with occurrence noted at 313, 294, 261, 238, 176, and 136 sites, respectively. Factors found to affect weed occurrence along Mississippi Delta roadsides included topographical characteristics, weed species, ditch slope, road type, and nearby land use. Among roadside topographical characteristics, road shoulder was found to strongly affect weed occurrence. In addition, paved and gravel road types with moderate roadside slope explained most of the variability of weed occurrence at each sampling site. Additionally, nearby arable land use affected weed occurrence more so than natural, residential, and pastoral land. Barnyardgrass, johnsongrass, and Palmer amaranth were 3.6 to 4.3 times more likely to occur than all other species identified. An effective weed management plan along eastern Arkansas–Mississippi Delta roadsides should focus on road shoulder, adjacent arable land use, road type, and specific weed species (e.g., Palmer amaranth, johnsongrass, and barnyardgrass). The inclusion of these parameters in future weed control programs can prove invaluable for preventing the spread of the herbicide-resistant Palmer amaranth, barnyardgrass, and johnsongrass.