Program '11: Lessons from 2010

The summer of 2010 was a rough one and an experience that nobody wants to repeat. While new problems like bacterial wilt received a lot of attention in 2010, in reality it was an old problem that caused the majority of damage to creeping bentgrass putting greens in North Carolina: Pythium root rot.


Pythium root rot is brought on by wet soil conditions; temperature doesn't matter. Since there are several Pythium species that can cause root rot, the disease can develop at any time of year as long as the soils are wet. We see Pythium root rot all throughout the year, and even diagnosed a case of it in western North Carolina last week.

Because it needs wet soils, Pythium root rot is most common in poorly drained greens. However, the disease can also occur in newer, well-drained greens if wet weather conditions persist for long enough. That's where spring of 2010 comes into play. Many areas in North Carolina experienced prolonged wet weather conditions during March and/or May, which triggered the development of Pythium root rot.

Our clinic was inundated with cases of Pythium root rot on creeping bentgrass during the first week of June. As soon as the weather turned hot, the plants with weakened, Pythium-infected roots were the first to decline. Most golf courses managed to survive through the initial heat wave in June, but hot and wet weather in July and August finished-off a lot of greens.

The problem is that most fungicide programs for creeping bentgrass greens include no fungicides for Pythium root rot until mid-June. Why wait until June? It's based on the misconception that Pythium diseases only develop during hot weather. We now know with 100% certainty that's not the case.


If you look at average daily rainfall in Raleigh, for example, you'll see that there is no pronounced wet season. Other than drier periods in April and late November, we get about 0.12 to 0.15" of precipitation per day on average from May through November. So when can we expect to see Pythium root rot activity? Any time between May and November, depending on when the rain comes in that particular year.

So what are you supposed to do, spray Pythium fungicides constantly from April through November? You could, but you'd be wasting a lot of money. The key is to adjust your fungicide program as needed during the year based on weather conditions: if it's wet, then treat the greens preventively for Pythium root rot. You simply can't write a Pythium root rot program on the calendar.

To find out more about Program '11, please visit our project website.

Pythium Root Dysfunction Alert

Multiple cases of Pythium root dysfunction, caused by Pythium volutum, have been confirmed in our lab from golf courses with creeping bentgrass putting greens throughout the Piedmont and Coastal Plains of North Carolina. The warmer than usual weather conditions have warmed the soil temperatures well into the optimum range for PRD development.

If you've had problems with PRD in the past, then you should have already started your preventative program. Don't worry if you haven't, there's still time to correct this issue before summer arrives. Remember, this is a ROOT DISEASE, therefore you must WATER-IN your fungicide applications to be successful!

For more information about PRD, including specific control recommendations, click here.

Introducing Program '11: The best fungicide program for your putting greens

Developing a fungicide program for putting greens is becoming increasingly complex, thanks mostly to an explosion in the number of products available to turf managers. When I came to NC State in 2002, I think there were about 60 different fungicide products available in the turf market. Now there are at least 120. It's enough to make your head spin.

It's little wonder that many golf course superintendents have gone toward 'canned' fungicide programs developed by university researchers or crop protection companies.

The problem with these programs is that every golf course is different. Just because a program works well on my research green in Raleigh doesn't mean it will work well on your greens. Different environments, microclimates, management practices, cultivars, construction methods, etc. - all of these things influence the potential for diseases to develop.

Furthermore, every year is different. The activity of a given disease can shift by a month or two depending on the weather conditions. Fungicide programs cannot be inked on the calendar and followed like a prescription. They have to be constantly tweaked and adjusted based on the hand that Mother Nature deals you.

So what is Program '11? This is a fungicide program that is specifically tailored for your putting greens, and adjusted for the specific conditions of 2011.

Over the next 6 months on this blog, we'll be chronicling a field experiment where we compare the performance of different fungicide programs, including one dubbed Program '11.  Program '11 was specifically designed for our research green and will be adjusted during the season based on the weather conditions. Along the way, we'll take a more detailed look at how you can develop and implement effective fungicide programs for your putting greens.

You can follow our progress in a number of ways -  choose one or all!

Visit our website! turfpathology.org/pages/program11.aspx

Like us on Facebook: facebook.com/turfpathology

Follow us on Twitter: twitter.com/ncturfpathology

RSS Feed for Email or Google Reader: feeds.feedburner.com/turfpathology

Hit two birds with one stone using the DMIs

Although it's not yet officially spring, temperatures across North Carolina are becoming conducive to two common spring diseases: dollar spot and fairy ring. Now's the best time to initiate preventive fungicide programs for these diseases.

The dollar spot pathogen becomes active when low temperatures are consistently above 50ºF, especially when combined with heavy dew formation during the night. Looking at the forecast for the next week, low temperatures will remain in the low- to mid-50s for about another week in Wilmington, Raleigh, Greensboro, and Charlotte.

For greens established with creeping bentgrass, we recommend initiating preventive fungicide treatments for fairy ring when 5-day average soil temperature reaches 55ºF. Most of North Carolina will be hitting that mark over the next week as well.

Our recent research shows that the DMI fungicides, like Bayleton, Torque, Tourney, and Triton, are very effective for fairy ring prevention. These treatments, even though they are watered into the soil, will also provide excellent dollar spot control because the DMIs are translocated upward in the plant. So, in the current environment where everyone is looking to save money, the DMIs are an excellent way to control both dollar spot and fairy ring with one application!

For more information, please visit our disease profiles on dollar spot and fairy ring, or the Disease Management Utility for assistance in selecting a fungicide and application rate.

Pythium root rot in March?

We diagnosed a case of Pythium root rot on a creeping bentgrass sample that was submitted to the Turf Diagnostics Lab last week. Really? Pythium root rot in March?

Most people don't start to think about Pythium diseases until June or July, but in reality they can occur at almost any time of year. We routinely see symptoms of Pythium root dysfunction as late as October or as early as February.

Pythium root rot can also occur at any time of year. There are many different species of Pythium that can cause root rot, and while most grow at warm or hot temperatures, some others grow at cooler temperatures. The disease is driven by soil moisture: if the soils are wet for extended periods of time, then Pythium root rot can develop. In the case of the sample that was submitted last week, the symptoms appeared after heavy rainfalls over the prior weekend.

I'm not saying that everyone needs to run out and apply a Pythium fungicide. But if you've had issues with Pythium root rot in the past, and you see more wet weather in the forecast, then it might be a good idea.

For more information about Pythium root rot and its management, refer to the disease profile on Turffiles.

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.

How's the spring dead spot?

This is probably the most common question I get this time of year as everyone anxiously waits to see how much disease there will be this year or if their preventive fungicide applications worked. Based on our winter weather conditions, with cold temperatures combined with periods of wet and dry weather, I expect the disease to be pretty severe this year and early reports seem to indicate that it's going to be a bad year. We've even had a report of a severe outbreak of the disease on zoysiagrass fairways.

Unfortunately, my travel is limited this time of year due to classes and conferences, so let me ask you: How's the spring dead spot out there? Any particular successes or failures with fungicides? Please post a comment to let us know what you're seeing!

The best time for fairy ring prevention is near

Average daily soil temperatures in NC on March 6, 2011

The time for preventative fungicide applications for fairy ring control will be approaching over the next couple of weeks. Based on our field research, two applications of a DMI fungicide beginning when soil temperatures reach a 5 day average of 55F provides excellent control.

If you would like to monitor soil temperatures on your own, you can do so using the NC State Climate Office Advanced Map. For sandy soils or sand-based putting greens, the average daily soil temperature will be very close to the average daily air temperature, so you don't necessarily need a website or fancy weather station. Just take the average of today's high and low temperature, and when that number is at or above 55F for 5 straight days, it's time to pull the trigger!

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