Weed interference and control in sugarbeet (Beta vulgaris L.) in the Gharb region of Morocco

Field experiments were conducted to evaluate the impact of weed interference duration and weed control strategies on growth and sucrose yield of fall-seeded sugarbeet in the Gharb region (Morocco). Sugarbeet showed a great capacity to recover from early weed interference, but the recovery did not prevent sucrose yield loss. Sugarbeet sucrose yield was reduced by 99 to 100% by full-season weed interference, and by 5 or 10% if weeds were allowed to interfere with sugarbeet for 2 to 2.5 or 5 to 5.5 weeks after sugarbeet emergence (WAE). Cumulative leaf area duration (LAD cum ) explained differences in sucrose yields between weed interference durations and weed control strategies, and higher LAD cum was the result of higher leaf area expansion rate. Yield loss could be prevented with increased number of hand-weedings if the first two hand-weedings were executed early in the growing season. Three hand-weedings during the sugarbeet canopy establishment phase permitted sucrose yield similar to sugarbeet kept weed-free from 4 WAE until harvest. POST phenmedipham plus sethoxydim gave insufficient weed control and resulted in sucrose yield reductions of 76 to 81%, compared to weed-free sugarbeet. However, a single hand-weeding following POST phenmedipham plus sethoxydim improved sucrose yield by 280 to 350%, compared to sucrose yields obtained with POST herbicides alone. The combination of POST herbicides and one hand-weeding gave a sucrose yield higher than or equal to sucrose yield from sugarbeet hand-weeded three times. Nomenclature: Phenmedipham, (3-[(methoxycarbonyl) amino] phenyl (3-methylphenyl) carbamate; sethoxydim, (2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio) propyl]-3-hydroxy-2-cyclohexen-1-one); sugarbeet, Beta vulgaris L.