Evaluation location: North Dakota, United States
A commercial field site near St. Thomas, in northeastern North Dakota, was selected for the 1999 Beta germplasm trial due to consistently high Sugar beet root maggot (SBRM) populations in the vicinity. Forty entries (treatments) were planted on 17 May into single-row plots (22-inch row spacing) that were 35 ft in length. Experimental design was a randomized complete block with four replications of treatments. A commercial variety (Maribo 9363) was included as a susceptible standard. SBRM population levels in the northern Red River Valley of North Dakota and Minnesota were severe during the 1999 growing season. Plant stand counts were very low for the majority of this experiment. Maribo 9363 had a DI of 5.88 and an average of only 19 surviving plants per 35 ft of row, whereas, the same variety had a mean density of 44.5 plants during 1998. Low stand counts were largely due to severe SBRM larval feeding injury that often caused the severing of sugar beet tap roots and eventual plant mortality.