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“Sugarbeet Report” presented by NDSU Extension, features growing tips from NDSU sugar beet specialists and researchers.
Bruce Sundeen:
This is the Sugar Beet Report, bringing you the latest information from NDSU throughout the Sugar Beet growing season. If you grow sugar beet, you are all too familiar with cercospora leaf spot. To battle this devastating disease, research is key. Our guest is Nate Wyatt, USDA research plant pathologist in the Sugar Beet and Potato Research Unit. Nate, your research covers latent cercospora. What is latent cercospora and how do you diagnose it?
Nate Wyatt:
The latent cercospora infection is the asymptomatic infection that occurs before you see actual symptoms in the field. And over the last 3 years, starting in 2021, we've had a pilot project going where we are using a molecular assay to detect cercospora in the field before we see it. And in those 3 years and again in this year, what we see is a really consistent trend of increasing infection leading up to the 1st week of July and occasionally just prior to in the last week of June. For Cercospora's sake, it's a really interesting time point, because that also tends to coincide with row closure.So the pathogen in this case is situating itself for that row closure event that provides an optimal micro environment in the under canopy for it to grow and thrive in that humid wet environment.
Bruce Sundeen:
How has the early planting in cool wet weather impacted cercospora's growth?
Nate Wyatt:
We had some pretty consistent weather patterns over the last 3 years in 2021, 2022 and 2023, where we had normal winters, we had pretty wet springs and then we had very dry summers leading up and through the middle of August. This year, we have a pretty unique situation where our winter was exceptionally light. We saw temperatures in February March reach upwards of 40 degrees Fahrenheit. And this spring has been abnormally wet. And so when we think about how that might impact Cercospora and its latent infection cycle, we know that excess moisture is what Cercospora thrives on. And so we would anticipate an advancement of Cercospora latent infection on a increased timescale compared to previous years. What we're seeing in the lab right now is sort of half and half of that. In some regions, we see exactly what we would anticipate with the more advanced Cercospora infection progressing earlier than normal, but in other regions, not so much. And we can come up with some potential hypothesis surrounding that, but really there's nothing conclusive we can say at this point as to why that might be occurring. Some of the factors that might be involved are just the overall inoculum levels in the Red River Valley may have actually been reduced over the last 3 years of low disease pressure. And that can be in combination with really good management practices and the introduction of CR plus into the Red River Valley.
Bruce Sundeen:
Do producers need to change their approach to cercospora because of the weather?
Nate Wyatt:
Given the difference in weather conditions we've seen this year relative to the previous 3 years, when you think about management of Cercospora, you can look to your coop managers and your coop recommendations for when you should be applying fungicides, with what chemistries and what tank mixes. We regularly communicate with those co ops and co op managers and they're very up to date on our weekly results from our cercospora latent infection survey and all of the results coming out of our lab.
Bruce Sundeen:
Nate, what about CR plus sugar beet varieties? Are they still effective against cercospora?
Nate Wyatt:
What we know is that there are cercospora isolates that are adapted to CR plus. We've identified those and they are present. We don't know what their frequency is in the population at this time, but this is why it's extremely important to manage your CR plus fields in a similar way to how we manage non CR plus fields. By doing so, we maintain the CR plus as a useful management tool moving into the future.
Bruce Sundeen
Thanks, Nate. Our guest has been Nate Wyatt, USDA research plant pathologist in the Sugar Beet Potato Research Unit. This is the Sugar Beet Report, bringing you the latest information from NDSU throughout the Sugar Beet growing season.