Response of Sugarbeet Varieties and Populations to Postemergence Herbicides

Injury from herbicides may reduce sugarbeet yield or sugar content. Previous research has shown a differential response of sugarbeet varieties to herbicides. We evaluated the growth response of fourteen sugarbeet varieties, and four USDA sugarbeet entries (three USDA experimental hybrids and their pollinator) to postemergence applications of the micro-rate of desmedipham plus phenmedipham (1:1 ratio) at 0.09 kg ai/ha plus triflusulfuron at 0.004 kg ai/ha plus clopyralid at 0.023 kg ae/ha plus methylated seed oil at 1.5% v/v. Sugarbeets were sprayed three times at weekly intervals beginning at the cotyledon growth stage. Sugarbeet varieties differed in their response to micro-rate herbicide applications. Leaf area, fresh weight and dry weight of Hilleshog E-17 and ACH 555, two diploid varieties, were not reduced by micro-rate applications, while the leaf area of Beta 5400 and Beta 5736, two triploid varieties, was reduced by 24 and 35%, respectively, compared to their respective untreated controls. In a second experiment, the leaf area and fresh and dry weight of Spartan and Hilleshog E-17 were not reduced by postemergence microrate applications in the growth chamber or field, compared to their respective controls. Hilleshog E-38, ACH 185, and Beta 5736 had significant reductions in leaf area and dry weight in the growth chamber and field, while RH-5 had significant reductions in the growth chamber only, and tolerance was not correlated with ploidy level. Among the USDA materials, reductions in growth measures were evident in all entries; however, reductions in the experimental hybrid with SP85576 cms were markedly less for all traits except growth chamber dry weight (27% reduction in fresh weight, 20% reduction in leaf area and 16% reduction in