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“Sugarbeet Report” presented by NDSU Extension, features growing tips from NDSU sugar beet specialists and researchers.
This is the Sugar Beet Report, bringing you the latest information from NDSU throughout the sugar beet growing season. Just saying the name, cercospora leaf spot for some sugar beet farmers is like nails on a chalkboard. Cercospora's spread is lower this year, but there are other issues. We're talking with Ashok Chanda, extension sugar beet pathologist with the University of Minnesota and Northwest Research and Outreach Center in Crookston, Minnesota. Ashok, how does the sugar beet crop look so far, and is our weather pattern good or bad for cercospora leaf spot?
Ashok Chanda:Yes, Bruce. Overall, the sugar beet crop looks pretty good. But, if you look at the weather, there are 2 things that are important for establishment of cercospora leaf spot. Number 1, the warmer temperatures. Number 2, moisture. When I say moisture, it's just the relative humidity. Right? So the amount of leaf wetness that is directly proportional to the amount of cercospora that you can see. So if you look at the weather from the 3rd week of July until the 1st week of August, more or less, we had very conducive weather for development of cercospora leaf spot. So that's when the growers were receiving a lot of text messages saying that disease infection values are moderate to severe, and it was time to apply some fungicides. Now we are seeing some cercospora leaf spots in most of the fields that we scouted so far, but I would say, generally, it's a little bit slower this season. It really wrapped up ending early week of July.
Bruce Sundeen:Ashok, why do you think we're seeing low cercospora this year compared to previous years?
Ashok Chanda:I would say there are 2 main reasons for this. Number 1, I think we're using more of the CR plus varieties, which have high tolerance to cercospora leaf spot. Number 2, I really want to congratulate the growers for doing an amazing job in starting early in terms of applying fungicides and staying on track, you know. Earlier applications and timely applications are really critical, especially, you know, in the early stages of disease development before cercosporalis part can go not be out of control.
Bruce Sundeen:Are CR plus sugar beets developing any cercospora in your field trials?
Ashok Chanda:Yes, Bruce. We are evaluating CR plus varieties in terms of cercospora. This is a 3rd year of research trials. Typically, we inoculate or create artificial disease pressure in the 1st week of July, and now we wait with the mother nature to help for disease development. So what we are seeing is every year, we're seeing the disease development a little bit earlier. So in 2022, it was not until September 1st that we saw some disease development on CR plus beats, which is 8 weeks after inoculation. In 2023, it was middle of August. That's about 6 weeks after we inoculated. Come to 2024, this year, as early as August 2nd, that's only 4 weeks after inoculation. So so what it's telling us is the number of cercospora isolates that are able to infect the CR plus varieties are on the rise. So as we have more and more buildup of these isolates, we definitely can see cercospora developing earlier in the season on CR plus. So that's why it's critical to have this fungicide applications earlier in the season.
Bruce Sundeen:Ashok, when it comes to fungicide applications, what are some important things to keep in mind?
Ashok Chanda:It's important to use fungicide mixtures, especially, you know, mix a broad spectrum fungicides such as Bancozeb with a triazole fungicide, you know, which is very selective. Also, rotate fungicides with different modes of action between the applications. And spray volume is really important because, you know, you want to really cover the canopy. So use at least 15 to 20 gallons volume if you're using a ground sprayer. And if it's a aerial application, say at least, you know, 5 gallons per acre. Again, spray intervals are critical as well. Typically, it's 10 to 14 days. But if you have lots of rain between applications, you should reduce interval to about 7 days.
Bruce Sundeen:Thanks, Ashok. Our guest has been Ashok Chanda, extension sugar beet pathologist with the University of Minnesota and Northwest Research and Outreach Center in Crookston, Minnesota. This is the Sugar Beet Report, bringing you the latest information from NDSU throughout the Sugar Beet growing season.