Evaluation location: North Dakota, United States
A grower-owned field site near St. Thomas, North Dakota was selected to evaluate Beta germplasm accessions for potential resistance to SBRM feeding injury. The experiment was planted on 9 May, 2012. No planting-time or postemergence insecticide protection was applied to any plots. Individual treatment plots were single rows that were 28 ft (8.5 m) long and spaced 55.9 cm (22 inches) apart. Experimental design was a randomized complete block with four replications of 34 treatments. Treatments included 30 accessions of B. vulgaris maritima that were obtained from the NPGS Beta collection, courtesy of the USDA-ARS Western Regional Plant Introduction Station (Pullman, WA). Four additional entries (i.e., FC704, PI-608437, PI-658654, and Triton) were included for comparative purposes. The commercial hybrid entry, Triton, served as the susceptible control. Larval feeding injury was assessed on up to ten sugarbeet roots per plot and rated in accordance with a 0 to 9 scale (0 = no damage and 9 = 75% or more of root surface blackened with feeding scars or a dead plant) on 13 August. Most SBRM fly activity occurred during early to mid-June, and peaked on 8 June at 136 flies per trap per day. This was a relatively high level of activity in comparison to most previous years. Root maggot feeding injury in the more susceptible entries was also moderately high compared to other years of testing. The lowest SBRM feeding injury in the test (i.e., 1.7 on the 0 to 9 rating scale) was recorded for PI-608437 (F1016). PI-608437 incurred significantly less feeding injury than all other entries, except FC704 and PI-658654 (F1024), which had average root injury ratings of 2.22 and 2.97, respectively. Other entries that had significantly lower SBRM feeding injury than the susceptible commercial hybrid (Triton) included the following: PI-518307, PI-518319, PI-518326, PI-518339, PI-518345, PI-518360, PI-518414, PI-540694, and PI-604507.