Field studies were conducted to investigate the effects of different rates of herbicides on weed control, agronomic characteristics, and quality of sugar beet at Shiraz, Iran, in 2000 and 2001. Separate and combined applications of herbicides, including 14 combinations and different rates of grass and broadleaf herbicides, at two rates were used. Herbicides reduced weed biomass compared with the weedy check. In both years, maximum reduction in weed biomass was observed with desmedipham plus phenmedipham plus ethofumesate at 0.23 0.23 0.23 kg ai/ha and desmedipham plus phenmedipham plus propaquizafop at 0.46 0.46 0.1 kg ai/ha. Efficacy of grass herbicides was reduced when they were combined with pyrazon. Highest crop injury in both years was observed with desmedipham plus phenmedipham plus ethofumesate at 0.23 0.23 0.23 kg/ ha. Highest and lowest root yields in both years were produced in weed-free and weedy check plots, respectively. All herbicide treatments produced lower sugar beet yields than the hand-weeded check. Of the herbicide treatments evaluated, the highest sugar beet yields were with desmedipham plus phenmedipham plus propaquizafop at 0.46 0.46 0.1 kg/ha in 2001 and with desmedipham plus phenmedipham plus ethofumesate at 0.23 0.23 0.23 kg/ha in 2000. Sucrose content and other sugar beet brei characteristics were not affected by the herbicide treatments.

Nomenclature: Desmedipham; ethofumesate; phenmedipham; propaquizafop; pyrazon; sugar beet, Beta vulgaris L. ‘IC-1’.

Additional index words: Competition, weed biomass, weed density.

Abbreviations: DAP, days after planting; DAT, days after treatment; POST, postemergence; WAP, weeks after planting.