2006 Annual Report 4d.Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and North Dakota State University. This project was initiated on June 1, 2004 and research is ongoing. The overall objectives of this project are to identify sunflower cultivars which are less susceptible to Sclerotinia head rot and to study chemical and biological control options for managing this disease. Please refer to the report for project 5442-21220-010-00D, Sclerotinia Diseases, for additional information. In 2005, this project was substantially modified. In past years, the results have proven very beneficial to breeding programs in evaluating progeny from crosses. However, considerable reluctance exists in releasing information to growers without a broader base of data on disease susceptibility. To remedy this void, the screening nursery was expanded to additional sites. The initial screening was conducted in Carrington and the Agriculture and Agrifoods Canada Station in Morden, Manitoba. Breeding programs were required to submit some commercial hybrids and not only breeding lines, to assure that the project will generate information useful to growers. Also new in 2005, the best 20 entries from the previous year’s head rot and stalk rot initial screenings were re-evaluated at these two sites, as well as at the NDSU Langdon Research Extension Center and South Dakota State University, Brookings. Our objective is to identify sunflower germplasm with improved resistance to both head and stalk rot. This set of 20 entries was also evaluated for stalk rot resistance at multiple sites. The initial screening nursery was successfully established at both sites in 2005. At Carrington, excellent infection was achieved, with impressively low variability in the data. Infection at Morden was low (possibly due to hear), but modifications were identified to improve methodology. For the 2006 season, only the Carrington data was used to select repeat entries. The repeat nurseries were established at all sites in 2005. Carrington and Langdon infection levels were excellent, with very good agreement between the data from the two sites. No useable data was collected at Morden (low infection, possibly due to hear) and Brookings (rabbit damage). Fungicide treatments were evaluated in 2005 in Carrington, Langdon, and Morden. A core set of treatments was developed, based upon labeled products and results of Sclerotinia fungicide trials on other crops. Investigators at some sites included additional treatments to study the efficacy of other products and rates. Carrington and Morden data showed some benefit from select treatments, but further improvements are needed. At Langdon, an evaluation of a series of adjuvants showed significant promise. Further modifications to the project were made in 2006. The Brookings site was dropped and sites for the repeat evaluation were added at the NDSU Oakes Irrigated Research Site and the University of Minnesota – Crookston. Trials have been established at all sites as planned. Publications and presentations: Bradley, C., and B. Henson. 2005. Sclerotinia management. Carrington Research Extension Center Annual Field Day, 19 July. Henson, B. 2005. Sunflower hybrid tolerance to Sclerotinia. Carrington Research Extension Center Row Crop Tour, 15 September. Henson, B. 2005. Progress in sunflower head rot screening. NDSU Research/Extension Fall Conference, 25 October. Henson, B. 2005. Progress in sunflower head rot screening (invited speaker). National Sunflower Association Board Meeting, Bismarck, North Dakota, 30 November. Henson, B. and T. Gulya. 2005. Sunflower disease management. Carrington Research Extension Center Crops Day, 13 December. Henson, R. A., S. Halley, T. Gulya, K. Y. Rashid, and M. A. Draper. 2006. Sunflower head rot screening nursery and fungicide evaluation. National Sunflower Association Sunflower Research Forum, Fargo, North Dakota, 11-12 January. www.sunflowernsa.com Henson, B., M. Swanson, P. Hendrickson, and M. Dahmer. 2005. Sunflower head rot screening nursery. 2005 Sclerotinia Initiative Annual Meeting, Bloomington, Minnesota, 18-20 January. Abstracts p. 41. Rashid, K. Y. 2005. Control of Sclerotinia head rot in sunflower. National Sunflower Association Sunflower Research Forum, Fargo, North Dakota, 11-12 January. www.sunflowernsa.com