The journey from an epidemic to success.
Agronomy & Pest Management
Mohamed Khan
Professor & Extension Sugarbeet Specialist
North Dakota State University
FARGO
Abstract
Minnesota and North Dakota produce 60% of the United States sugar beet, Beta vulgaris. One of the major limiting factors for sugar beet production is the foliar disease, Cercospora leaf spot (CLS) caused by the fungus Cercospora beticola. CLS destroys the leaves of the plants and thus affects the photosynthetic capability of the plants. This disease results in significant reduction in root yield, recoverable sugar, percent sucrose, and increases concentration of impurities resulting in higher processing costs. For many years, growers used fungicides in a rotational program to effectively control. However in 2016, growers in North Dakota, Minnesota and Michigan lost $200 million because of an epidemic as a result of the fungus developing resistance to the major fungicides used for its control. Research was conducted to determine how best to control CLS with experimental, labeled fungicides and experimental varieties with improved disease resistance. Results indicated that mixtures involving multisite with site specific fungicides effectively controlled CLS especially with the experimental (CR+) varieties. Research sites were used for demonstration at field days. Research results were disseminated to growers, other educators, and advisors of growers at seminars, production guide, reports, bulletins, and a radio program conducted during the growing season. Growers quickly adopted the research-based recommendations and successfully controlled Cercospora leaf spot from 2017. Limited amounts of CR+ varieties became available in 2021 and was used on 60% of acres at one Cooperative in 2021. These growers have ordered CR+ seeds for 95% of their acreage in 2022. Using mixtures and CR+ varieties will reduce fungicide usage by at least 33% and will lead to improved recoverable sucrose and profitability in the future.
Authors: Mohamed Khan
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Mohamed Khan Professor & Extension Sugarbeet Specialist, North Dakota State University & University of Minnesota, North Dakota, 58104