Abstract
An unintended outcome of crop production is losses due to abiotic factors including wind, water, and temperature. Defoliation of sugarbeet from hail can occur in any month throughout the growing season and can cause sugarbeet damage ranging from virtually undetectable damage to complete defoliation of vegetative plant material. Sugarbeet will almost always recover and continue their growth cycle unless hail causes stand loss which occurs mostly when sugarbeet are seedlings. Modern-day sugarbeet are diploid varieties as compared to tetraploid and triploid varieties characterized by heavy leaf texture and a large bush style plant architecture produced in previous decades. Experiments were conducted at multiple locations in 2021, 2022, and 2023 to measure vegetative index, root yield, and percent sucrose following simulated hail treatments at different growth stages and intensity with diploid varieties. Experiments were initiated in April and May when conditions were appropriate for cultivation by seeding at approximately 161,700 seed per hectare. Treatments were six sugarbeet rows spaced 56 cm apart and 9.1 m in length. Stands were thinned to approximately 180 sugarbeet per 30.5 m row in rows two through five when sugarbeet were at the 2-lf stage. Treatments were 0%, 25%, 50%, 75% and 100% (only petioles remaining) loss of canopy to simulate hail implemented by removing leaves from plants with hand shears in mid-July, early August and end of August. Health and density of the sugarbeet canopy was quantified approximately 21, 42, and 63 days after treatment (DAT) by collecting normalized difference vegetation index (NDVI) data with a RapidScan CS-45 active sensor (Holland Scientific, Lincoln, NE). Sugarbeet was defoliated and harvested mechanically in mid to late September from the center two rows of each plot and weighed. A 10-kg sample was collected from each plot and analyzed for sucrose content and sugar loss to molasses by American Crystal Sugar Company (East Grand Forks, ND). Sugarbeet canopy 21 days after the 25% and 50% canopy loss simulated hail treatment was greater than 90% of the 0% treatment at Crookston in 2022. All treatments were greater than 90% of the 0% treatment, 42 DAT. Further, canopy regrowth from simulated hail in late-August occurred at the same rate as canopy regrowth from simulated hail in mid-July or early August. Root yield and percent sucrose loss expressed as percent of the 0% simulate hail treatment increased as severity of the simulated hail event increased. Loss of root yield was greatest when simulated hail event occurred in July and was least in late August or calendar date closest to sugarbeet harvest. However, percent loss of sucrose was least in early July and greatest when simulated hail occurred in late August or calendar date closest to sugarbeet harvest. Finally, loss of root yield and sucrose was influenced by growing conditions following the simulated hail event, especially at the 75% simulated hail intensity. These outcomes tended to match results in the historical literature or from experiments conducted in the 1950 and 1960s with tetraploid and triploid varieties.