A cercospora leaf spot model for sugar beet: in practice by an industry

Sugar beet (Beta vulgaris L.) is planted on nearly 268,000 ha in the Red River Valley (RRV) of Minnesota and North Dakota and in southern Minnesota. This geographic region is the leader in sugar beet production in the United States, representing about 45% of the hectares planted and accounting for 50% of the tonnage produced annually. The most recent economic analysis by Bangsund and Leistritz estimated that the 1992 sugar beet crop in Minnesota and North Dakota had direct impacts (production and processing) at $575.5 million and secondary impacts at an additional $1.06 billion. The sugar beet industry in Minnesota and North Dakota consists of three grower-owned cooperatives. American Crystal Sugar Company (186,810 ha) includes five districts, each with a factory where sugar is extracted. The Minn-Dak Farmers Cooperative (37,320 ha) and the Southern Minnesota Beet Sugar Cooperative (43,590 ha) are large districts, each with a single factory. The RRV includes the American Crystal and Minn-Dak cooperatives. Distance from the northern to the southern borders of the three cooperatives spans about 560 km. This article reviews the history of Cercospora leaf spot in Minnesota and North Dakota, which culminated in development of a leaf spot model. It also covers implementation and evolution of the model during 10 years of application by the sugar beet industry. Limitations and benefits of the Cercospora leaf spot model are presented.