FARGO, N.D. — Cercospora beticola is the most economically damaging foliar disease farmers face, says Mohammed Khan, a Fargo-based Extension sugarbeet specialist at North Dakota State University and the University of Minnesota.
Khan has been doing his job for 22 years but the Cercospora history goes back a long time before that. Here is his look back on its history:
- 1926 — Farmers started producing sugarbeets in East Grand Forks, Minn., with seeds supplied by the company. Europeans improved varieties for yield, but with susceptibility to cercospora. American Crystal Sugar and other private companies prevented varieties that had higher cercospora susceptibility, even those which limited tonnage yields.
- 1974 — Farmers buy American Crystal, making it a cooperative. The farmer owners changed to an “open policy,” with higher yield potential but with cercospora controlled by fungicides. They used “tin” and Benlate fungicides. After two years of use, cercospora developed resistance and overtook Benlate.
- 1981 — The first major cercospora “epidemic” occurred in Minnesota and North Dakota.
- 1998 — A second big Cercospora epidemic cost American Crystal growers $40 million, and a total of $100 million for the region’s three co-ops. "We were going toward more susceptible varieties, but using one or two fungicides,” Khan said. Growers sprayed an average of 3.7 times across the growing region. Some applied fungicides nearly every week — 12 applications a year.
- 1999 — Environmental Protection Agency approves a Section 18 exemption for a QoI fungicide trade named “Quadris,” and then “Eminent,” a triazole. “That was that was the product that saved the industry,” Khan said.
- 2003 — EPA approves Headline and by 2005 fully approved Eminent and other triazoles. Fungicides controlled the disease at two applications in the northern Red River Valley, three in the southern Red River Valley, and four in Southern Minnesota.
- 2016 — Excessive and continuous rains and heat, increased the Cercospora incidence and the potential for fungus mutations that would make them resistant to fungicides. NDSU and growers asked seed companies to speed up development of resistant varieties that were becoming commercially available in 2021.
- 2021 — Growers in Minn-Dak Farmers Cooperative in Wahpeton, N.D., and Southern Minnesota Beet Sugar Cooperative at Renville, Minn., were among the first in the country to start using CR+ (cercospora resistance plus performance) beet seed.