June 22, 2026
By Claire LaCanne, University of Minnesota Extension Educator – Crops, Tom Peters, University of Minnesota Extension Sugarbeet Agronomist, and Dean Malvick, University of Minnesota Extension Field Crops Pathologist
During the June 17 Strategic Farming: Field Notes webinar, Extension specialists Tom Peters and Dean Malvick discussed updates in sugar beet and disease management, moderated by Anthony Hanson, Extension Educator - Integrated Pest Management. The session highlighted updates and challenges for sugar beet management, including pest management and the onset of disease pressure.
of the acreage that is in the United States. Sugar beets are usually grown in a rotation that includes grass and broadleaf crops, with sugar beets following a grass crop about once in every four years. In the southern areas, sugar beets are usually after corn, and in the north, after spring wheat.
Beet development is coming along, and the crop is looking especially excellent in central Minnesota around Kandiyohi, Renville, and Meeker counties. Fields have closed rows in those areas, which is about two weeks ahead of schedule as we tend to see row closure closer to the 4th of July. This is a good indicator of a strong crop in that area. Other more northern locations are certainly more variable due to cooler conditions, but also wind events that affected sugar bee growth and development. Some areas even had to replant due to those wind events.
The dryer than average conditions in some of these sugar beet growing areas are not super conducive to great growth, and timely rains would help.
Another focus of Tom’s Extension work has been using different weed management methods like plant population, cultivation and weed zappers, and cover crops or nurse crops, in addition to chemical control. Tom thinks that the development of artificial intelligence (A.I.) tools that assist precision agriculture and targeted weed control has the potential to dramatically impact integrated weed management as well.
For his parting thoughts, Tom iterates that there are three main challenges sugar beet growers face. These are: 1) getting a good stand of sugar beets, 2) controlling weeds, and 3) controlling foliar diseases, the top disease challenge being cercospora leaf spot.
Dean Malvick observes that seedling problems have been found, and Rhizoctonia trials in Waseca have shown significant disease progression and stand loss in plots inoculated with the pathogen. There’s not much we can do for many root and stem diseases during the season. It’s valuable to record where issues are happening this year so that we can plan for disease management during the next growing season, including planning for selecting soybean varieties or fungicidal seed treatments.
Sudden Death Syndrome (SDS) is not as likely to occur in droughty conditions, but might be occurring in areas that have had more rainfall. If we don’t get early adequate rains, SDS is less likely to pop up or progress as severely, as a general rule of thumb, because SDS seems to need wet soils during the first two to three weeks after soybean seed is planted. Variety selection and seed treatments are the main management tactics for SDS as well, so observe where issues are occurring this year to plan for the next growing season. SDS is not widespread in northern Minnesota, but it has been spreading more to the northwest in recent years. If you have suspected samples of SDS, please submit photos to the Crops Team’s Digital Crop Doc!
At this point, we are beyond the stage where we would get most of the other seedling diseases, which would occur a little sooner, but be sure to scout your fields and document what you’re seeing, because it’s always good to know if a seed treatment package is effective against the prevailing pathogens and diseases in your fields.
Red crown rot of soybean is newer in Minnesota and has only been confirmed in Rock County so far. If you see plants that are dying and look similar to Rhizoctonia or maybe SDS, but not quite right, or you just don’t know, please report these incidents of suspected red crown rot so we can get an idea of where it’s occurring in the state. Red crown rot typically progresses later in the season, usually seeing it in the field in August.
We are ahead of white mold season right now, but keep that disease in mind as well. White mold is primarily a problem when the soybeans are flowering, the canopy is full, and we have cool, wet weather keeping the foliage and soil wet. If we don't have those conditions, we usually don't really get much white mold. It is a little too early to predict the risk, but early R2 is a good time to apply fungicides for white mold.
For corn, tar spot has been starting to develop at very low levels in central Iowa and Nebraska. We have not seen or heard reports of tar spot in Minnesota yet this year, but we could start to see this in the next 2-3 weeks, especially if the weather stays cool and we get occasional rains.
By Claire LaCanne, University of Minnesota Extension Educator – Crops, Tom Peters, University of Minnesota Extension Sugarbeet Agronomist, and Dean Malvick, University of Minnesota Extension Field Crops Pathologist
During the June 17 Strategic Farming: Field Notes webinar, Extension specialists Tom Peters and Dean Malvick discussed updates in sugar beet and disease management, moderated by Anthony Hanson, Extension Educator - Integrated Pest Management. The session highlighted updates and challenges for sugar beet management, including pest management and the onset of disease pressure.
Overview of sugar beets in Minnesota
We grow about 1,100,000 acres of sugar beets in the United States. All of our sugar beets are processed into sugar that is part of our diets. In Minnesota and North Dakota, we grow about 635,000 acres of sugar beets, which represents about 60%of the acreage that is in the United States. Sugar beets are usually grown in a rotation that includes grass and broadleaf crops, with sugar beets following a grass crop about once in every four years. In the southern areas, sugar beets are usually after corn, and in the north, after spring wheat.
Beet development is coming along, and the crop is looking especially excellent in central Minnesota around Kandiyohi, Renville, and Meeker counties. Fields have closed rows in those areas, which is about two weeks ahead of schedule as we tend to see row closure closer to the 4th of July. This is a good indicator of a strong crop in that area. Other more northern locations are certainly more variable due to cooler conditions, but also wind events that affected sugar bee growth and development. Some areas even had to replant due to those wind events.
The dryer than average conditions in some of these sugar beet growing areas are not super conducive to great growth, and timely rains would help.
Insect presence
Sugar beet root maggot is the most significant insect pest in sugar beets, and it has been abundant in the northern part of the valley this year - areas like Marshall and Polk counties for example, and it is likely there will be challenges with root maggot. Presence is high, but peak fly timing will be impacted by the weather. Fly development may be delayed because of the cooler weather, which will hopefully be good for sugar beets.Weed control in sugar beets - and a look back on Tom’s career
Tom shared news that he is retiring this summer, prompting a bit of a retrospective and look forward into sugar beet management. From the time that Tom started his Extension position in 2014 until now, he has observed the development of glyphosate resistance in more weeds in sugar beets - the top culprit being waterhemp, but also ragweed and kochia. This means Tom has had to emphasize strategies to control waterhemp in sugar beets and the whole cropping sequence, because frankly, the best products we have for waterhemp control are those that can be used in the rotational crops.Another focus of Tom’s Extension work has been using different weed management methods like plant population, cultivation and weed zappers, and cover crops or nurse crops, in addition to chemical control. Tom thinks that the development of artificial intelligence (A.I.) tools that assist precision agriculture and targeted weed control has the potential to dramatically impact integrated weed management as well.
For his parting thoughts, Tom iterates that there are three main challenges sugar beet growers face. These are: 1) getting a good stand of sugar beets, 2) controlling weeds, and 3) controlling foliar diseases, the top disease challenge being cercospora leaf spot.
Disease management
Along the line of diseases, rainfall has been variable across the state, which can be seen on the U.S. drought monitor map. Some areas have been abnormally dry while others have had enough or even more than enough moisture. Weather conditions significantly impact disease development, and two early season diseases of soybean that can be affected by large amounts of rain are Phytophthora root rot of soybean and Rhizoctonia root and stem rot. Both of these prefer wet to very wet soil, with Phytophthora thriving with periods of saturation.Dean Malvick observes that seedling problems have been found, and Rhizoctonia trials in Waseca have shown significant disease progression and stand loss in plots inoculated with the pathogen. There’s not much we can do for many root and stem diseases during the season. It’s valuable to record where issues are happening this year so that we can plan for disease management during the next growing season, including planning for selecting soybean varieties or fungicidal seed treatments.
Sudden Death Syndrome (SDS) is not as likely to occur in droughty conditions, but might be occurring in areas that have had more rainfall. If we don’t get early adequate rains, SDS is less likely to pop up or progress as severely, as a general rule of thumb, because SDS seems to need wet soils during the first two to three weeks after soybean seed is planted. Variety selection and seed treatments are the main management tactics for SDS as well, so observe where issues are occurring this year to plan for the next growing season. SDS is not widespread in northern Minnesota, but it has been spreading more to the northwest in recent years. If you have suspected samples of SDS, please submit photos to the Crops Team’s Digital Crop Doc!
At this point, we are beyond the stage where we would get most of the other seedling diseases, which would occur a little sooner, but be sure to scout your fields and document what you’re seeing, because it’s always good to know if a seed treatment package is effective against the prevailing pathogens and diseases in your fields.
Red crown rot of soybean is newer in Minnesota and has only been confirmed in Rock County so far. If you see plants that are dying and look similar to Rhizoctonia or maybe SDS, but not quite right, or you just don’t know, please report these incidents of suspected red crown rot so we can get an idea of where it’s occurring in the state. Red crown rot typically progresses later in the season, usually seeing it in the field in August.
We are ahead of white mold season right now, but keep that disease in mind as well. White mold is primarily a problem when the soybeans are flowering, the canopy is full, and we have cool, wet weather keeping the foliage and soil wet. If we don't have those conditions, we usually don't really get much white mold. It is a little too early to predict the risk, but early R2 is a good time to apply fungicides for white mold.
For corn, tar spot has been starting to develop at very low levels in central Iowa and Nebraska. We have not seen or heard reports of tar spot in Minnesota yet this year, but we could start to see this in the next 2-3 weeks, especially if the weather stays cool and we get occasional rains.
Sugar beet field.
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