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Since 2013, the glucose content of all beet samples from beet reception and field trials is routinely analyzed in The Netherlands using a biosensor which is integrated into the automatic beet laboratory system. The invert sugar content is subsequently calculated from the glucose content using a linear conversion factor. This additional information helps to identify beet deliveries with a questionable beet quality at an early stage and provides valuable information on various agronomic factors that increase invert sugar accumulation in the beet. Based on results obtained during the past years, different factors are highlighted that affect the invert sugar content in the beet. Among these factors, beet deterioration following frost damage and the presence of root rot due to infestation by pests and diseases have shown to increase the invert sugar content dramatically. In addition, unfavorable storage conditions and bad harvesting quality had a substantial impact on invert sugar accumulation. Growth conditions and beet variety also influenced the invert sugar content markedly, although to a much lesser extent. Using the obtained data, the most important control measures that enable growers to prevent undesired invert sugar formation and consequent sugar losses in their beet are discussed.

A method by high-performance liquid chromatography (HPLC) with UV-detection was developed for the determination of the active substances hymexazol, tefluthrin, sedaxane, fludioxonil, metalaxyl-M, thiamethoxam, imidacloprid, clothianidin and β-cyfluthrin in pelleted sugar beet seed. The method performance was investigated in a round-robin study in 2021. In this study, ten laboratories analyzed 15 different seed samples, provided by five manufacturers. For each sample, two representative portions of 100 pelleted seeds were analyzed. In general, the highest recovery rates were obtained using an extraction solvent consisting of 95% acetone, 4% water and 1% phosphoric acid and this solvent was therefore selected as the preferred solvent for the simultaneous extraction of the different active substances from the pelleted seeds. However, slightly higher recovery rates for hymexazol were obtained using a mixture of 80% acetone, 19% water and 1% phosphoric acid. This solvent remains an alternative for the analysis of hymexazol. The presented and validated method may serve as an internationally recognized reference method for the analysis of different fungicides and insecticides in pelleted sugar beet seeds from different origin.

Different seed storage methods, varying in storage temperature, moisture and/or oxygen content, were applied to commercial sugar beet seed lots from four breeding companies. After storage for 10–11 months, germination of the seed was tested in the laboratory (cold test, 10°C). In addition, the contents of active ingredients (fungicides and insecticide) were analyzed and compared with the initial contents before storage. Based on these results, a selection of the most promising storage methods was made to test plant emergence in a field experiment. This research was performed in 2015/16 and in 2016/17. In both years, two storage treatments outperformed the others: these were storage in a closed jar with the addition of moisture absorber (i.e. silica gel) at room temperature and storage at –18°C in a closed plastic bag. Using these two storage methods, seed vigour and contents of active ingredients were comparable to those in seed that had not been stored for one year. Based on the results from this study, the advice to growers for a successful storage of residual sugar beet seed was adjusted in 2017, after including some practical guidelines and considerations.