What Disease?

If I had a wooden nickel for every time someone has said the following to me in the past few weeks, I'd be able to build a raging fire ... "I bet you are swamped with samples in the clinic right now with all the rain we've had, etc. etc., etc." Actually, outside of a few oddball cases, we haven't seen or heard of any major disease problems on creeping bentgrass putting greens. The missing link has been heat stress. If we look back at our records, some of our busiest years have been those that were hotter and drier which ultimately leads to more stress on the plant therefore making them weaker and more susceptible to infection by pathogens.

One of the oddball cases we have diagnosed in the past couple weeks has been summer patch on creeping bentgrass putting greens. The symptoms of summer patch appear as circular patches or rings, ranging from 6 inches to 3 feet in diameter. Turf within these patches initially turns off-colored, is prone to wilt, grows poorly, and may appear sunken in the turf stand. Over a period of a few weeks, the turf continues to decline, turns yellow or straw brown and eventually collapses to the soil surface. The outer edges of the patch are usually orange or bronze when the disease is actively developing. The patches recur in the same spot annually, and can expand at a rate of 2 to 4 inches per year.

Summer patch symptoms on creeping bentgrass

The summer patch fungus attacks the roots, stolons, and rhizomes in the spring when soil temperatures reach 65°F. Summer patch symptoms are rarely seen during the early stages of disease development, instead, the symptoms appear in mid-summer after considerable damage has been done to the root system. Heat, drought stress, and nutrient deficiencies are the main factors that encourage the expression of summer patch symptoms. In North Carolina, the symptoms typically appear in early to mid-July.

For more information about summer patch, including control recommendations, click here.

Finally, if any of you are wondering about Pythium root rot, we have only diagnosed a handful of cases thus far with all of those happening within the past 7-10 days. In every case, we have found the Pythium to be active in the upper thatch layer around roots closest to the plant. With that being said, if you are treating for Pythium root rot, don't water those fungicides in TOO much. We typically recommend about an 1/8" ... which in most cases equals about 3-4 minutes with part circle heads. Either way, you may want to take the time to see just how long it takes to put that amount out.

Pythium root rot following drainage route

For more information about Pythium root rot, including control recommendations, click here.

Guess What? Pythium LOVES Water!

If you've learned nothing else about turfgrass diseases, fungi love water and while not technically a fungus, the oomycete Pythium absolutely adores water. Now, you're sitting there thinking "boy, it sure has been wet lately across much of North Carolina, especially in western NC, and instead of reading this blog post, I should be firing up my sprayer and putting out something to prevent Pythium diseases." Well, if that's not the thought you had ... you better switch gears and make it happen.

Rainfall Estimates for Last 30 Days

For those of you managing bermudagrass putting greens or if you're trying to grow in a freshly seeded stand of anything, you better be on the look out for Pythium blight. We have diagnosed Pythium blight on 'Champion', 'Mini Verde', and 'Tifeagle' bermudagrass putting greens over the past couple of weeks. They are not bullet proof folks! We've also seen a lot of yellow patch on the ultradwarfs, but we'll save that for another day.

For those of you managing creeping bentgrass putting greens, you better be starting up your Pythium root rot prevention program. Two of the biggest misconceptions associated with Pythium and creeping bentgrass is that Pythium blight is common on putting green heights and Pythium root rot only occurs during the hot days of summer. Both are false. We rarely see Pythium blight on creeping bentgrass at putting green heights, especially if it's a well established mature stand. We have diagnosed Pythium root rot on creeping bentgrass putting greens in North Carolina in every month except the winter time.

For more information about Pythium blight and root rot, including control recommendations, visit the links below.

Pythium Blight

Pythium Root Rot

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

Pythium Root Rot: History Repeating?

The summer of 2010 shouldn't be too distant of a memory for most and if you remember correctly, most of NC ended May on a very wet note. This was followed by one of the hottest summers on record. This series of events led to widespread cases of Pythium root rot on creeping bentgrass putting greens, especially for those who did little to nothing to protect their roots from Pythium during May.

With all that being said, you should be applying products for Pythium root rot prevention RIGHT NOW.  Doing so now will save you money and headaches come summer.

For more information about Pythium root rot, including control recommendations, click here.

Remember that Pythium root rot is a soil disease, so you MUST water your applications in to be effective.

May 2012 Rainfall Total

May 2011 Rainfall Total

May 2010 Rainfall Total

Program '11 Update: Stress

A lot has happened since the last update I posted on July 22. We had record attendance of 650 at our NC State Turfgrass Field Day on August 10. Classes are in session, conference season is starting up, and we had an earthquake AND a hurricane in one week. I sincerely hope that everyone who was in the path of Hurricane Irene escaped severe damage.

From mid July to mid August was hot, humid, and stressful for bentgrass putting greens in North Carolina, with 18 days above 95 and 6 days above 100. The low temperature only dipped below 70 degrees once during this time.

We've made several changes to Program '11 in response to the prevailing weather patterns. In response to the severe stress imposed by the weather conditions, we decided to apply Signature + Daconil on August 1 instead of Stellar + Daconil. On August 15, the weather was cooling off and we decided to drop the Alude application and applied Spectro alone.

On August 29, in the wake of Irene, we applied Honor instead of Subdue + Fore. While there was some potential for Pythium root rot development in these wet conditions, we were more concerned about the explosion of dollar spot and brown patch we were observing in untreated areas on the research farm.


All of the programs have continued to provide excellent disease control. No significant amounts of dollar spot, brown patch, anthracnose, or Pythium root rot have been observed in the treated plots. The Bayer Program has continued to express more yellow spot symptoms as I reported in July. This program contains a lot of QoI fungicides, which we've found increase the intensity of yellow spot symptoms.

On July 25, Program 13, NC State Program, BASF Program and Program '11 all exhibited excellent turf quality. Beginning in early to mid July, all programs declined in their turf quality, except for the BASF program which actually continued to slightly improve. Plots treated with the BASF Program has significantly better turf quality than all others on August 16 and 22. The Syngenta Program improved in its turf quality and by August 29 was statistically similar to the BASF Program while all the others were significantly lower.

It is difficult to determine why the BASF Program held up so well during the hot and humid conditions of early July. These plots were treated with a tank-mixture of Segway, Iprodione Pro, and Daconil Ultrex on August 8, which may have helped to control some underlying Pythium root rot or other disease. Perhaps the application of Honor on July 11 helped to precondition the bentgrass for the oncoming stress as BASF promotes.

Program '11 Update: Dollar spot and Pythium root rot

We're only two months into our Program '11 Project and are already seeing major differences among the fungicide programs we're evaluating. Here's an update on things:

We've already made a number of changes to the Program '11 treatment because of the continuing cool and wet conditions. Dollar spot pressure has been very high for the last month, and frequent rainfalls have increased the risk for Pythium root rot development. Here are the changes we've made so far:

1. We were scheduled for a Bayleton application on April 4 for fairy ring prevention, but the soil temperatures were too cool. Instead, we moved-up the application of Honor originally scheduled for April 11 because the weather was very favorable for Pythium root dysfunction and dollar spot.
2. The Bayleton treatment for fairy ring was applied on April 18 when 5-day average soil temperatures finally reached 55F.
3. Due to an outbreak of dollar spot in the Program '11 plots, we made an emergency application of Daconil + Torque on April 29. Therefore, we cancelled the application of Torque that was originally scheduled for May 2.
4. Instead of applying Signature + Banol on May 9, we decided to go with Banol + 26GT on May 12 due to continuing dollar spot pressure and wet conditions favorable for Pythium root rot.

Now to the results:

• Clemson's Program 13, which hasn't received any fungicide treatments yet, is getting hammered by dollar spot as you would expect
• The NC State Program has also failed to provide acceptable control of dollar spot. This is probably due to the intense dollar spot pressure this spring combined with the watering-in of most treatments for fairy ring and PRD.
• The Bayer, Syngenta, BASF, and Program '11 treatments are providing good to excellent dollar spot control.

Turf quality is primarily being affected by dollar spot, so the treatments that are providing good dollar spot control are exhibiting the best turf quality right now. The Bayer and Program '11 treatments have the highest turf quality because they are providing the best dollar spot control. Program 13 and the NC State Program are not providing acceptable turf quality at this point.

For more information about our Program '11 Project, or to follow along on Facebook or Twitter, please visit our website turfpathology.org.

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 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.