2003 SUGARBEET RESEARCH AND EXTENSION REPORTS. VOLUME 34, PAGE 300-304 EVALUATION OF ZONE TILLAGE, FUMIGATION, AND A SYSTEMIC ACQUIRED RESISTANCE INDUCER ON RHIZOMANIA OF SUGARBEET Carl A. Bradley 1 , Mohamed F. R. Khan 2 , Norman R. Cattanach 3 , and Randy S. Nelson 3 1 Extension Plant Pathologist, North Dakota State University 2 Extension Sugarbeet Specialist, North Dakota State University and Univ. of Minnesota 3 Research Specialist, North Dakota State University Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is becoming more prevalent in the Red River Valley sugarbeet production region and is nearly endemic in the southern Minnesota sugarbeet production region. Resistant cultivars and crop rotation have been the main tactics used to manage the disease. More rhizomania management options may be needed in the future due to the recent spread of the ‘P’ strain in Europe and appearance of a new strain of BNYVV in California that are able to cause disease on Rhizomania-resistant cultivars that use the ‘Holly’ gene (Harju et al., 2002; Liu et al., 2003). The effect of tillage has not been evaluated for effects on rhizomania. It is possible that deeper tillage prior to planting may allow better drainage and better root growth thus providing a less adequate environment for disease infection. The use of fumigation has been evaluated for control of rhizomania in California, Texas, and the United Kingdom (Harveson and Rush, 1994; Henry et al., 1992; Martin and Whitney, 1990), but has not been evaluated in North Dakota and Minnesota. The systemic acquired resistance (SAR) inducer 1,2,3-benzothiadiazole-7-thiocarboxylic acid-S- methyl-ester manufactured by Syngenta and known as Actigard in the U.S. and BION in Europe has been evaluated for control of rhizomania of sugarbeet in Germany (Mouhanna and Schlosser, 1998). OBJECTIVES The objectives of the two studies presented herein were: i) to evaluate the effects of zone tillage on rhizomania of susceptible and resistant cultivars; and ii) to evaluate the effect of fumigation with Telone II and seed treatment with Actigard on rhizomania of susceptible and resistant cultivars. MATERIALS AND METHODS Both the tillage study and the fumigation/SAR study were conducted at the rhizomania nursery in Glyndon, MN. A minimum of 5 plants per plot were collected for BNYVV testing. Root hairs were removed from each beet and analyzed using a double-antibody sandwich enzyme-linked immunosorbent assay (DAS ELISA) technique with a BNYVV reagent set (Agdia, Elkhart, IN). Absorbance values of each ELISA reaction were obtained using an ELISA plate reader at 405 nm. Specific details regarding the field components of each study are contained below. Tillage study. A steel shank was used to till the soil at a 12 in. depth for half of the plots immediately prior to planting. The shank was positioned so that it would be directly in each row of sugarbeet plants (zone tillage). Plots were either planted to the rhizomania-resistant cultivar Van der Have H46177 or the rhizomania- susceptible cultivar Crystal 952 on 23 May 2003. Plots were harvested 1 Oct 2003. Plots were 6 rows wide on 22 in. centers, 30 ft long, and organized as a 2 x 2 factorial in a randomized complete block design with 3 replications. The general linear model procedure (PROC GLM) in SAS (SAS Institute, Inc., Cary, NC) was used for statistical analysis. Fumigation/SAR study. Two chemical treatments were evaluated and compared to an untreated control in this study. The treatments consisted of: plots fumigated with Telone II (dichloropropene) at 12 gal/acre on 6 Nov 2002, plots planted to seed treated with Actigard 50WG (1,2,3-benzothiadiazole-7-thiocarboxylic acid-S-methyl- ester) at 3 g/kg seed, and an untreated control. Plots were either planted to the rhizomania-resistant cultivar Van der Have H46177 or the rhizomania-susceptible cultivar Crystal 999 on 12 May 2003. Plots were 6 rows wide