Cercospora Leaf Spot Waiting for Opportunity

Cercospora leaf spot symptoms are not showing in the sugar beet fields…yet. Let’s find out how the sugar beet crop looks with Eric Branch, NDSU and University of Minnesota Extension sugarbeet specialist.

What is Sugarbeet Report?

“Sugarbeet Report” presented by NDSU Extension, features growing tips from NDSU sugar beet specialists and researchers.

Bruce Sundeen: 00:00

This is the Sugarbeet Report, bringing you the latest information from NDSU throughout the sugar beet growing season. Cercospora leaf spot symptoms are not showing up in the sugar beet fields yet. Let's find out how the sugar beet crop looks with Eric Branch, NDSU and University of Minnesota extension sugar beet specialist. Eric, how's the crop looking right now? Yeah.

Eric Branch: 00:22

So now we're approaching the end of June, and we're approaching row closure, which is a critical period for the sugar crop in this region. And, you know, overall things are looking okay. Some variation from our challenging spring in terms of the wind and everything like that. But I think we can be at least a little optimistic, you know, as long as we get the right environment. Bruce, there's no substitution for good sunshine and good heat that I think are gonna be very important coming up.

Bruce Sundeen: 00:46

Well, speaking of environments, what's going on in the fields? What's the focus?

Eric Branch: 00:50

The environment as we hit the warmer, more humid temps that we can look forward to coming up in July, we see a critical time for Cercospora leaf spot. And as a pathologist, that's what I'm all about. The Cercospora leaf spot consumes all my brainpower all year round, Bruce, but between May and September, of course. Growers who by now are getting to point of row closure have either made their first fungicide application or will be doing so very shortly. And, you know, I like to hear that. I like to see those sprayers out. That is the number one thing that we can do to ensure a good crop.

Bruce Sundeen: 01:18

What's important about spraying?

Eric Branch: 01:20

Cercospora leaf spot, it's caused by a fungal pathogen, Cercospora beticola, and this fungal pathogen reproduces spores every ten to fourteen days, so spraying at an interval in order to have a consistent protection on the leaves, so spraying every ten to twelve days. So there is a fungicide that is preventative and can prevent those spores from germinating and causing infection.

Bruce Sundeen: 01:42

Why is it important to follow a specific regime to control Cercospora?

Eric Branch: 01:46

So last year in Minnesota, North Dakota was a really rough year for Cercospora leaf spot. There is a lot of inoculum left over from that year in the region, and if we have hot humid periods, we will expect a huge disease risk and a lot of symptoms to develop later on. Right now we have no symptoms in the fields. However, we do have confirmation of latent infections in the region. Going forward we'll see that increase from thirty percent to, greater levels of infection. These are asymptomatic infections, no visible symptoms, but that fungal pathogen is inside the leaves and just waiting for that right time when the rows close, the humidity increases, temperature increases in July, and infections and symptoms can develop.

Bruce Sundeen: 02:26

And what's the best way to be prepared?

Eric Branch: 02:28

And the best way to keep those fungicide applications on regular intervals, ten to twelve days, and tank mix using multiple chemicals at once in order to manage fungicide resistance. We wanna see all of our chemicals work together in pairs, right? We apply a single site fungicide such as a DMI or a Triazole fungicide mixed with a multi site like Mancozeb, an EBDC group product, the combination of hitting the pathogen with two of these tools at once leads to pretty good results and over the long term can help manage resistance.

Bruce Sundeen: 03:00

Eric, what's the downside of ignoring treatment?

Eric Branch: 03:03

The downside of not following our best practices is these are best practice for a reason. These are evidence based practices that show that the number one way to have a good crop and protect the investment that is the Sugarbeet crop every year is to indeed have these short intervals and tank mixing. We wanna control this disease this year and the better we can do controlling Cercospora this year, the better we'll have in future years as well, both from the fungicide resistance side and then just that level of disease severity inoculum in the environment as well.

Bruce Sundeen: 03:31

Thanks, Eric. Our guest has been Eric Branch, NDSU and University of Minnesota Extension Sugarbeet Specialist. This is the Sugarbeet Report, bringing you the latest information from NDSU throughout the sugar beet growing season.