Field studies were conducted from 2005 to 2009 in Idaho and Oregon to 1) evaluate the competitive effect of volunteer potato on sugar beet yield (volunteer potato competition experiment), and 2) determine the optimum timing of volunteer potato removal from glyphosate-tolerant sugar beet fields using glyphosate (volunteer potato removal timing experiment). The volunteer potato competition experiment consisted of eight potato densities, including the untreated check: 0, 6,741, 10,092, 13,455, 16,818, 20,184, 26,910, and 40,365 tubers ha−1. The volunteer potato removal experiment consisted of 10 removal timings (including the untreated check) ranging from the 10-cm rosette stage to mid-tuber bulking. There was a linear decrease in sugar beet root and sucrose yield as volunteer potato density increased (P < 0.001) such that with every volunteer potato tuber per square meter, sugar beet root yield decreased by 15% and sucrose yield decreased by 14%. At the highest volunteer potato density (40,365 tubers ha−1), sugar beet root yield was 29,600 kg ha−1 (compared to 73,600 kg ha−1 for the untreated), representing a 60% reduction in sugar beet root yield. In the removal timing study, a one-time application of glyphosate at the 10-cm rosette, hooking, and tuber initiation stages provided 74% to 98% reduction in volunteer potato tuber biomass. Delaying volunteer potato removal beyond the tuber initiation stage reduced sugar beet root and sucrose yield (12% to 20%), resulting in an economic loss of $104 to $161 per hectare. The best potato removal timing that optimizes the trade-off between improved control and potential for sugar beet yield reductions is before or at the tuber initiation stage.

A prepackaged mixture of desmedipham + phenmedipham was previously labeled for control of Amaranthus spp. in sugarbeet. Currently, there are no effective POST herbicide options to control glyphosate-resistant Palmer amaranth in sugarbeet. Sugarbeet growers are interested in using desmedipham + phenmedipham to control escaped Palmer amaranth. In 2019, a greenhouse experiment was initiated near Scottsbluff, NE, to determine the selectivity of desmedipham and phenmedipham between Palmer amaranth and sugarbeet. Three populations of Palmer amaranth and four sugarbeet hybrids were evaluated. Herbicide treatments consisted of desmedipham and phenmedipham applied singly or as mixtures at an equivalent rate. Herbicides were applied when Palmer amaranth and sugarbeet were at the cotyledon stage, or two true-leaf sugarbeet stage and when Palmer amaranth was 7 cm tall. The selectivity indices for desmedipham, phenmedipham, and desmedipham + phenmedipham were 1.61, 2.47, and 3.05, respectively, at the cotyledon stage. At the two true-leaf application stage, the highest rates of desmedipham and phenmedipham were associated with low mortality rates in sugarbeet, resulting in a failed response of death. The highest rates of desmedipham + phenmedipham caused a death response of sugarbeet; the selectivity index was 2.15. Desmedipham treatments resulted in lower LD50 estimates for Palmer amaranth compared to phenmedipham, indicating that desmedipham can provide greater levels of control for Palmer amaranth. However, desmedipham also caused greater injury in sugarbeet, producing lower LD50 estimates compared to phenmedipham. Desmedipham + phenmedipham provided 90% or greater control of cotyledon-size Palmer amaranth at a labeled rate but also caused high levels of sugarbeet injury. Neither desmedipham, phenmedipham, nor desmedipham + phenmedipham was able to control 7-cm tall Palmer amaranth at previously labeled rates. Results indicate that desmedipham + phenmedipham can only control Palmer amaranth if applied at the cotyledon stage and a high level of sugarbeet injury is acceptable.

Understanding the effects of crop management practices on weed survival and seed production is imperative in improving long-term weed management strategies, especially for herbicide-resistant weed populations. Kochia [Bassia scoparia (L.) A.J. Scott] is an economically important weed in western North American cropping systems for many reasons, including prolific seed production and evolved resistance to numerous herbicide sites of action. Field studies were conducted in 2014 in a total of four field sites in Wyoming, Montana, and Nebraska to quantify the impact of different crop canopies and herbicide applications on B. scoparia density and seed production. Crops used in this study were spring wheat (Triticum aestivum L.), dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.), and corn (Zea mays L.). Herbicide treatments included either acetolactate synthase (ALS) inhibitors effective on non-resistant B. scoparia or a non–ALS inhibiting herbicide effective for both ALS-resistant and ALS-susceptible B. scoparia. Bassia scoparia density midseason was affected more by herbicide choice than by crop canopy, whereas B. scoparia seed production per plant was affected more by crop canopy compared with herbicide treatment. Our results suggest that crop canopy and herbicide treatments were both influential on B. scoparia seed production per unit area, which is likely a key indicator of long-term management success for this annual weed species. The lowest germinable seed production per unit area was observed in spring wheat treated with non–ALS inhibiting herbicides, and the greatest germinable seed production was observed in sugar beet treated with ALS-inhibiting herbicides. The combined effects of crop canopy and herbicide treatment can minimize B. scoparia establishment and seed production.

The objective of this WSSA Weed Loss Committee report is to provide quantitative data on the potential yield loss in sugar beet due to weed interference from the major sugar beet growing areas of the United States and Canada. Researchers and extension specialists who conducted research on weed control in sugar beet in the United States and Canada provided quantitative data on sugar beet yield loss due to weed interference in their regions. Specifically, data were requested from weed control studies in sugar beet from up to 10 individual studies per calendar year over a 15-yr period between 2002 and 2017. Data collected indicated that if weeds are left uncontrolled under optimal agronomic practices, growers in Idaho, Michigan, Minnesota, Montana, Nebraska, North Dakota, Ontario, Oregon, and Wyoming would potentially lose an average of 79%, 61%, 66%, 68%, 63%, 75%, 83%, 78%, and 77% of the sugar beet yield. The corresponding monetary loss would be approximately US$234, US$122, US$369, US$43, US$40, US$211, US$12, US$14, and US$32 million, respectively. The average yield loss due to weed interference for the primary sugar beet growing areas of North America was estimated to be 70%. Thus, if weeds are not controlled, growers in the United States would lose approximately 22.4 million tonnes of sugar beet yield valued at approximately US$1.25 billion, and growers in Canada would lose approximately 0.5 million tonnes of sugar beet yield valued at approximately US$25 million. The high return on investment in weed management highlights the importance of continued weed science research for sustaining high crop yield and profitability of sugar beet production in North America.

Phytotoxic effects of metabolites from a naturally occurring rhizobacterial isolate, Pseudomonas syringae strain 3366, were determined on downy brome and ‘Hill 81’ winter wheat, along with 10 other weed and crop species. Centrifuged supernatant and concentrated ethyl acetate extracts from aerobic shake cultures of strain 3366 suppressed germination of seeds and reduced root and shoot growth in agar diffusion assays, soil assays, and under field conditions. Generally, root growth was inhibited more than shoot growth. Strain 3366 metabolites applied in soil inhibited all species tested. Crude ethyl acetate extracts in soil inhibited downy brome at concentrations that had little effect on winter wheat. Inhibitory activity was greater in Palouse silt loam (pH 5.8, 3.6% organic matter) than in Shano silt loam (pH 9.0, 0.8% organic matter). Activity of extracted metabolites decreased rapidly in wet soil but remained high in dry soil. Active metabolites were isolated and purified from the ethyl acetate extract using column chromatography, thin-layer chromatography, and crystallization. Chemical analysis revealed the presence of phenazine-1-carboxylic acid, 2-amino phenoxazone, and 2-amino phenol. Activity of these metabolites against downy brome was confirmed in agar assays. Phenazine-1-carboxylic acid, the major identifiable metabolite present in ethyl acetate extracts (20% by weight), inhibited downy brome root growth by 99% at concentrations of 5.7 mg L−1. Production of these metabolites in field soil by live bacteria of strain 3366 was confirmed with thin-layer chromatography.

The performance of a mechanistic simulation model of crop-weed competition was evaluated with data on the effects of weed density, relative time of weed emergence, and environmental conditions on crop yield for three different crop-weed combinations. Reductions in crop yields due to weed competition were simulated accurately for all experiments, except for one case in which severe water stress combined with weed competition altered crop morphological development (height and leaf area). The mechanistic model was then used to assess the potential and constraints of two empirical models of crop-weed competition, one based upon weed density and relative time of emergence, and the other on relative leaf area. The empirical model describing the relationship between relative leaf area of the weeds shortly after crop emergence and yield loss appeared to have several advantages for management applications, whereas the mechanistic model is more suited for research purposes.

Whole-plant bioassays using sugar beet, lettuce, cucumber, green bean, pea, and soybean as test crops were used to detect mesotrione residues in the soil. The test crops were planted in soil treated with mesotrione in the field the previous year at rates of 0 to 560 g ai ha−1 and in nontreated soil from the same field, with mesotrione added at concentrations of 0 to 320 μg kg−1. Experiments were conducted in the greenhouse for a 21-d period. Values for the dose giving a 50% response (I50) were predicted using a log-logistic nonlinear regression model. I50 values (mean ± SE) of 8.6 ± 1.8, 14.9 ± 2.0, 29.8 ± 11.0, 41.6 ± 7.3, 52.9 ± 6.4, and 67.9 ± 30.3 g ai ha−1 for sugar beet, lettuce, green bean, cucumber, pea, and soybean, respectively, indicate that these crops were effective bioassay test species for quantifying mesotrione residues. A greenhouse bioassay was a simple and sensitive tool to detect mesotrione at concentrations of less than 1.0 μg kg−1 with sugar beet and lettuce being the most sensitive test species. The I50 values for soil treated with known concentrations of mesotrione were lower than for field soil treated with mesotrione the previous year. Knowing the level of mesotrione residues in the soil, growers have flexibility in crop rotations following mesotrione use on corn. Growers can use this information to minimize risk of crop injury by choosing appropriate rotation crops that suffer little or no yield reduction.

New trends in crop breeding include analytical approaches to identify metabolic fingerprints that can be used for associations to the genetic background. The biochemical phenotype, as a result of plant endogenous factors and interaction with the environment, has the potential to increase the accuracy of forecasting regarding agronomical quality factors. In this study a metabolite profile analysis by gas chromatography–mass spectrometry (GC–MS) was conducted on sets of seed material from sugar beet. One set represented high-performing varieties with a close genetic background and with a similar quality in terms of germination capacity. The second set contained seed lots from different genotypes comprising different germination capacities. By multivariate statistical analyses high variance in both sample sets was revealed. These data were further allocated to corresponding metabolite classes. It could be shown that an untargeted GC–MS approach has the power to resolve differences in the molecular phenotypes of related offspring lines. Metabolic profiles were found to correlate more to genotypic differences than to differences in the germination capacity.

Cell cycle activity in dry and germinating untreated and treated (soaked in water and subsequently in fungicide) seeds of two sugarbeet cultivars, collected at commercial harvest time (late mature seeds) and about 2 weeks before this (immature seeds), was investigated by flow cytometry, and by immuno-detection of β-tubulin and the B-subunit of the 11 S globulin. Germination capacity and field emergence were tested. With dry seeds of both cultivars, higher G2 / G1 ratios were observed in the radicle tips of late mature seeds, as compared with those from immature seeds. The late mature seeds contained more partly degraded (soluble) B-subunit of 11 S globulin, typical of germinating or primed sugarbeet seeds. Thus events associated with the onset of germination had occurred in the seed lots collected at commercial harvest time. The cytoskeleton protein β-tubulin was not detectable in dry seeds from either harvest. Western blotting revealed an accumulation of β-tubulin during germination and this was faster in the late mature harvested seeds which was correlated with the onset of DNA replication. Soaking enhanced the rate of cell cycle activation during germination as well as vigour, germination capacity, and field emergence. There was positive correlation between the G2 / G1 ratio and the traits examined in laboratory and field tests. It is concluded that a combined analysis of proteins and cell-cycle-related events can be used in understanding and predicting sugarbeet seed quality.