Sugarbeet research aims to target when fungicides should be applied

Sugarbeet research is underway to more specifically identify when plants should get fungicide treatment for cercospora leaf spot disease.

A field of sugarbeets.
Research underway by Nathan Wyatt, USDA-ARS research plant pathologist, aims to finetune when sugarbeets should be sprayed for cercospora leaf spot.
Contributed / NDSU
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FARGO, N.D. — A project underway by a research plant pathologist at U.S. Department of Agriculture's Agricultural Research Service aims to find a way to more efficiently control cercospora leaf spot disease in sugarbeets and to reduce fungicide resistance to the pathogen.

The research of Nathan Wyatt, who works in the Edward T. Schafer Agricultural Research Center's Northern Crop Science Laboratory in Fargo will be conducted during the next few years to fine tune the model that predicts when the risk of cercospora leaf disease is at a level at which growers can respond by spraying fungicides on the sugarbeets.

Mohamed Khan, North Dakota State University and University of Minnesota sugarbeet specialist, called cercospora leaf spot disease the most important problem facing growers during a talk at the Sugarbeet Research and Reporting Session held in January 2022.

The sugarbeet disease, which has potential to trim yields as much as 40% and reduce quality, results in major monetary losses and also decreases the storability of the crop, Peter Hakk, NDSU and U of M sugarbeet specialist, noted at the same research session.

For example, in 2016, cercospora leaf spot resulted in more than $140 million in sugarbeet losses in North Dakota and Minnesota, Hakk said.


Previous cercospora leaf spot disease research, based on the model known as Shane and Teng, was launched in 1984 and adjusted in 2003. That research identified weather conditions conducive to disease development.

“We’re looking at relative humidity and temperatures, at what threshold do you start to see cercospora leaf spot," Wyatt said. "They quantified a risk model through it so after a certain period of time at a certain relative humidity and temperature that day, they could put a zero to seven rating on how risky environmental conditions were for cercospora leaf spot to develop."

Daily infection values were averaged over 14- and 21-day periods to determine the favorable number of days for patogen development.

Wyatt will use that research, which identified weather conditions conducive to cercospora leaf spot disease development, together with new information about asymptomatic infection to devise more specific fungicide predictions.

The 2022 NDSU sugarbeet production guide recommends that farmers should start spraying fungicides when environmental conditions, including temperature and relative humidity, are favorable or when plants show symptoms of cercospora leaf spot disease. Farmers then spray every 10 to 14 days through the remainder of the growing season.

During the past two years, much more research has been conducted on the cercospora leaf spot pathogen’s biology, Wyatt said.

“We’re going to wrap our current knowledge of the pathogens and the biology we’ve gained over the past few years into an informative model about when we should be applying fungicides,” he said.

The goal of the research is not to eliminate spraying, but to develop a prediction model that won’t be based on a strict fungicide application schedule, Wyatt said.


That could lead to a reduction in spraying, which would reduce growers’ input costs. It also would help reduce resistance to cercospora leaf spot.

Data will be collected this summer, and field trials will get underway in 2023, Wyatt said. The goal is to have prediction models available for sugarbeet cooperatives in 2024.

Ann is a journalism veteran with nearly 40 years of reporting and editing experiences on a variety of topics including agriculture and business. Story ideas or questions can be sent to Ann by email at: or phone at: 218-779-8093.
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