The University of Idaho Sugarbeet RhizomaniaVariety Performance Tests, 2004.  John J. Gallian, Sugarbeet Specialist and Plant Pathologist, Dixie Vargas, Scientific Aide, University of Idaho, Twin Falls Research and Extension Center.

  Commercial and experimental Rhizomania resistant varieties adapted to the Idaho growing area were tested at the College of Southern Idaho Ag Endowment Farm at Twin Falls on a field leased by the Snake River Sugarbeet Research and Seed Committee for rhizomania research.  The field had been inoculated in 2000 with rhizomania-infested soil and susceptible sugarbeets were grown to establish disease. In the spring of 2004 soil was sampled to 24 inches, 50 lb N and 40 lb P₂O₅ applied per acre, and the field was double disked, roller harrowed, and bedded. Temik was applied in the bed at 18 lb/A.    Forty-three varieties plus 2 susceptible commercial checks were planted on April 27, 2004, with a research cone planter at a rate of 8 seeds/ft of row.  Nortron was applied at 3.0 pt/A broadcast basis in a 10-inch band on April 29, and the field was handline sprinkler irrigated with 0.5 inches of water on May 5 to activate the herbicide. 

  Experimental design was a randomized complete block replicated 8 times.  Plots were 4 rows wide (22 inch row spacing) by 25 ft long with a 5 ft alley separating each tier.  The test received serious hail damage on May 22 when most plants were in the cotyledon stage.  The first application of post-emergence herbicide was delayed for 10 days because of the injury.  A broadcast tank mix of Progress 21.0 oz/A, Upbeet 0.5 oz/A, and Stinger 6.0 oz/A was applied on June 1, and 40 lb/A N as ammonium nitrate was applied on June 2 to encourage recovery from the injury, immediately followed by cultivation and irrigation. A tank mix of Progress 24.0 oz/A, Upbeet 0.5-oz/A and Stinger 6.0 oz/A was broadcast applied on June 17, and Assure II 9.0 oz/A on June 18.  Plants were thinned to an 8-inch average spacing at the 2-4-leaf stage the week of June 7.

  All varieties were entered into the curly top nursery in Twin Falls, Idaho, operated by the Beet Sugar Development Foundation (BSDF) and were rated for resistance to curly top virus disease.  The trial was harvested on October 4-5.  Plants were machine topped and the two center rows of each plot were machine harvested using a two-row modified Farmhand 808 harvester.  Roots were weighed and 2 sugar and 1 tare sample (8 beets minimum per sample) were taken per plot. Each root in one border row for each plot in four replications were lifted and scored for rhizomania symptoms using a 0 to 9 rating scale, where 0 = immunity (no disease symptoms) and 9 = highly susceptible.  Sugar and tare samples were analyzed at the Amalgamated Sugar Company Tare Laboratory at Paul, Idaho.   Disease was uniform and moderate throughout the test. Yield data were adjusted according to tare values. 

  Bolting is an important consideration when choosing a variety.  On October 4, immediately prior to harvest, bolted plants were counted in the two center rows for every plot.  Percent bolters were calculated based an average of 72 plants/50 ft of row in each plot across the eight replications.  Five varieties had bolters and the percentages are given in the following table.  There were no bolters in any of the remaining varieties in the test.

Results of the standard rhizomania test are given in Table 11.  Average root yield per acre of the 3 highest performing varieties was 18.51 tons higher than the susceptible check varieties, and the average estimated recoverable sugar for the same varieties was 5125 lb/A higher than the susceptible check varieties. The disease index (DI) is the mean rating of all roots for each variety.  The percent resistance (% R) is the percentage of roots for each variety that had ratings of 0 to 3.