Fairy Rings and Fairy Tales

Fungi love water and here lately in North Carolina we've had plenty of water via record rainfall to help ensure they don't go extinct any time soon. The majority of fungi in this world are beneficial, because without these fungi we wouldn't have some of the finer things in life such as beer or Agaricus bisporus that adorns salads and pizzas as a topping. However, there are plenty of them that cause problems for us in the form of plant diseases.

You name a disease of turfgrass and we have likely observed it in the field or as a sample submitted to the NC State Turf Diagnostics Lab over the past 3-4 months. One that we rarely receive as a sample due to it's ease of identification is from a fairy ring. Most people associate fairy rings with mushrooms. To quote NC State alum Dr. Lee Miller, "not all fairy rings produce mushrooms and not all mushrooms produce fairy rings." This is important to remember, because if you observe mushrooms in your lawn, putting green, or croquet court, it doesn't necessarily mean you have a fairy ring problem.

A fairy ring in Raleigh, NC.

Fairy rings have likely peaked the interest of mankind since day one. This fascination has led to some crazy theories over the years such as fairies danced there the night before or that it was created by the fiery tail of a flying dragon. Whatever you do, don't step into the ring, collect the dew from the grass blades, or attempt to destroy it because bad luck is guaranteed to follow!

"Plucked from the Fairy Circle" - A man saves his friend from the grip of a fairy ring.

From British Goblins: Welsh Folklore, Fairy Mythology,Legends and Traditions (1880)

Fairy rings tend to form in circles, arcs, crescents, or broken rings. During their radial journey outward, fairy ring fungi decompose organic matter, which in turn releases nitrogen and other nutrients back into the soil for plants to take up. This is why the ring will often be darker green than the surrounding turf. The good news is that fairy ring fungi don't actually infect the turfgrass plant like brown patch, dollar spot, etc. The bad news is that they leave behind a coating on the soil particles that renders the soil hydrophobic (repels water) and may ultimately kill the turf. This is important to know when it comes to controlling the symptoms caused by fairy rings. For example, if you are treating fairy rings curatively in a home lawn situation, your best bet may be as simple as punching holes through the dead rings with something as fancy as an aerification machine or as simple as a pitchfork. Either way, you are instantly helping water penetrate the affected zone. If you are only observing green rings, then you may be able to mask them with a light fertilizer application. In severe cases or in high profile areas, you will likely want to use wetting agents and/or fungicides in addition to the aforementioned tips. 

For more information about fairy rings, including control recommendations, click here.

The Rundown

After a relatively quiet June at the NC State Turf Diagnostics Lab, turf samples have been rolling in during the month of July. Right after the record breaking heat wave experienced by North Carolina and much of the country, it seemed as if delivery trucks were backing up and dumping cardboard boxes of all shapes and sizes chocked full of ailing turfgrass samples.

One of the most common questions I get from golf course superintendents that I speak with on a weekly basis is "What are you seeing in the lab?" Well, here you go! Here's a rundown of the most common diagnoses we've made over the past two weeks.


Creeping Bentgrass Putting Greens

1. Pythium root rot
2. Fairy ring
3. "Warm-weather" brown patch (Rhizoctonia zeae)
4. Yellow spot
5. Anthracnose

Home Lawns

Zoysiagrass

1. Curvularia leaf spot

Bermudagrass

1. Heat/drought stress

Tall Fescue

1. Brown patch

Summer Solstice Welcomes Brown Patch

June is in full swing and so is brown patch in tall fescue lawns and landscapes.  Brown patch, caused by the fungus Rhizoctonia solani, is the most common disease in tall fescue during late spring and throughout the summer months in North Carolina.  Brown patch infections can start as early as April in some years with full blown outbreaks occurring by late May and early June in most years.  As the name implies, symptoms are brown to tan areas of turf that are roughly circular patches that range from a few inches to several feet in diameter.

Brown Patch Lesion on Tall Fescue Leaf

The two most common mistakes managers of tall fescue make are fertilizing too late or too much in late spring and over watering.  Tall fescue should not be fertilized after the first of May, unless you are using ultra low rates (< 0.25 lb N/M) with iron for a color effect.  The recommended amount of nitrogen on tall fescue per year is 3-4 pounds per 1,000 square feet.  Most people will apply a pound or two in the fall and a pound or two in the spring.  When in doubt, submit a soil test to ensure you're feeding your lawn the right nutrients at the correct amounts.

Watering should be done only as needed to prevent drought stress.  When you do apply irrigation, do it deep and infrequent instead of watering every day.  It is a common mistake for homeowners to set their irrigation system on a schedule and forget about it.  Remember, fungi love water and if you over water, you're giving the advantage to the fungi, not the turfgrass.  The ideal time to water your lawn is in the early morning hours before sunrise.  Irrigating during late afternoon or early evening is the worst thing you can do because this extends the leaf wetness period, however brown patch will love you for it!

Symptoms of Brown Patch in Tall Fescue

Need help knowing when and how much to water your lawn?  Try out our online water management tool at the following link.

http://turf-ims.ncsu.edu/

For more information about brown patch, including control recommendations, please visit the following link.

http://www.turffiles.ncsu.edu/Diseases/Brown_Patch.aspx

Is Emerald a poor curative for dollar spot control?

Over the years, I've heard a number of people say that Emerald is a slow or poor fungicide for curative control of dollar spot. I must confess that I've never understood what everyone is talking about.

Given that boscalid, the active ingredient in Emerald, controls fungi by depleting their energy reserves, it makes sense that it might be a little slow to work on a curative basis. However, in reality, I've always been impressed with it's activity on both a preventive and curative basis.


Let's look at a couple of examples. In this first curative dollar spot control study, we had an average of 40 to 45 dollar spot infection centers in each plot before initiation of treatments. That's not a huge amount of dollar spot on a 20 square foot plot, but certainly enough to warrant a curative fungicide application in a golf course setting.

On July 20, just 5 days after applying the low rate of Emerald, we reduced the number of infection centers down to 2 per plot, whereas the number in untreated plots held constant. So, the low rate of Emerald reduced dollar spot incidence by 95% in 5 days. I'd consider that to be pretty good curative activity! If you're expecting more than this out of a curative application, then you are probably expecting too much.


Looking at some older data, in 2006 we evaluated Emerald, Daconil + Emerald, and Daconil + Banner for curative dollar spot control. In this case, the dollar spot pressure was much more intense, with 150 to 200 dollar spot infection centers per plot before the initiation of treatments. After the first application on 19 Jun, dollar spot incidence declined in all of the treatments at a similar rate and none of the treatments were disease free until three weeks later on 10 Jul. And this is even though dollar spot disease pressure was much lower during late June and early July, as evidenced by the decline in the amount of disease in untreated plots.

Curative control of any disease is more dependent on the level of disease pressure, the amount of turf injury present, and the growth rate of the turf after the application. Which fungicide is applied probably isn't that important in most cases. In order for the disease symptoms to go away, the turf has to grow out of the symptoms and spread into the damaged areas. This, of course, takes time. There aren't any fungicides that will make dollar spot go away over night.

For a lot of reasons, we don't recommend controlling dollar spot on a curative basis. Perhaps the most important reason is that curative applications increase the risk for fungicide resistance to develop. If you find yourself in a situation where you need to make a curative application for dollar spot control, be sure that you are tank-mixing with chlorothalonil to reduce the potential for resistance to develop. This is especially important for products with a high resistance risk like Emerald.