Fairy ring is affected by several fungicides, but solid control takes some cultural work as well. Derek Settle, Ph.D., technical service specialist for the Green Solutions Team for Bayer CropScience LP, talks about the best ways to break up the ring before it causes damage.
What do we know about fairy ring?
Fairy ring’s always a major issue on the course. It’s difficult to control. Today, we know more about it than we ever have, and our strategies preventively in the spring are much better than they used to be. I’ll say our strategies curatively to get fairy ring during the growing season and the summer is now better.
It’s not a typical disease – it’s not directly pathogenic, but the side effects are just as damaging. Most of us consider and call it a disease, but a plant pathologist might disagree. Anyhow, it’s serious, and in a golf situation, it’s all about the greens, and it can be very devastating on sand-based putting greens.
How do we control it?
To control it, you have to realize it’s not on the surface, so you have to go down into the thatch layer and possibly deeper. Our fungicides don’t have good mobility within plants, and they definitely don’t move downward much at all. The ones that have some movement in the plant will kind of go in and up, so we’re always using high rates of fungicides. Then you have to determine where the fungus is active. The only way to do that is to take a look. At that point, you’ll look for the layer of mycelium – it can be either white or yellow, and sometimes it’s orange. Sometimes, the other test in the field is to take a slice across the ring and smell it. If it smells really strong like mushrooms, you can tell for sure you’ve got fairy ring.
There are a lot of patch diseases, and fairy ring has a lot of lookalikes. It could be brown patch or take-all patch or something else. So you have to figure out what it is for sure. Then you’ve got to figure out where it is and you’ve got to put your fungicide at the right depth. All those factors make it difficult to control. You have to realize too that most of the really significant damage occurs midsummer even though we’re timing our applications very early in the spring. We’ve got some really good preventive programs, but they’re planning way ahead for trouble that you don’t want to see midsummer.
So our best research was probably done by Lee Miller at NC State University when he was a student under Lane Tredway – Lee’s now at the University of Missouri. Prior to Lee, I’ll mention Mike Fidanza at Penn State, and he’s been working on it for years. Frank Wong also did a lot of work on it – sooner or later, if you’re a plant pathologist, you’re going to do some work on fairy ring. Miller came up with a temperature model, so now we know that when the five-day average soil temperature in the spring reaches 55 to 60 degrees at a two-inch depth, that’s when the first application goes down. For preventive programs, those first two applications are almost always typically DMI fungicides, and that’s a family that now has a lot of different fungicides. That provides typically the most consistent control.
So we go with these two fungicide applications about 28 days apart. I think the first app is according to the soil temperature. Then, with Bayer, after the first two apps, we suggest a third app 60 days later, and that would be ProStar, which would be a safe fungicide when it’s warm. With the DMI family you have to be careful when it’s warm. And you have to realize we’re using a high rate, so that’s also a factor. The DMIs can have growth regulation, and you don’t want to have that in the summertime.
The superintendent also has to use the information at his site to know whether or not he needs to water it in. Typically, for most greens, the fairy ring is going after the organic matter which is in the thatch. We know that’s usually in that upper inch to two inches, so you don’t have to water in too much – maybe about an eighth of an inch. But there are situations where you need to know that information. Based on the depth, you might need to go a quarter inch, and in some cases it might need to be even greater than that. But generally it’s not very deep. That’s where you get your knife out or take a sample and cut across the ring. Then you’ll see where the mycelium is active. That’s really important, because the fungicide is really only going to be effective if it comes in contact with the fungus.
What about cultural practices?
Absolutely, that’s no. 1 on the list. It’s all about managing the thatch and other organic matter that might be in the soil. Things like core aerification, vertical mowing and frequent topdressing of sand helps to reduce thatch as well as organic matter. That will minimize fairy ring. In the worst-case scenario, when you go on a green and they have raging fairy ring, nine times out of 10, the superintendent will tell you he had a situation where he was under a lot of pressure and they didn’t want him to core aerify, or maybe it was the guy beforehand. Then when you take a look at the profile, you’ll see a large amount of organic matter, and it’s typically thatch.
Cultural practices for thatch have practical purposes too. Greens are going to be softer if there’s a high amount of organic matter. It should be a win-win situation if it’s communicated properly. It improves rooting, it reduces fairy ring but then also the surface is going to be a harder, firmer surface, which is going to be better for the game of golf.
