More on the DMIs and Bermudagrass Greens

It is often said that good research raises more questions than it answers. Maybe the same can be said about blog posts? And no, I am not referring to Megan's California Gurls post from last Friday. (Side note: My main motivation for posting today was to bury that thing as quickly as possible. No pun intended.)

In last week's post about Torque for spring dead spot and fairy ring control, I casually mentioned that tebuconazole can injure ultradwarf bermudagrass putting greens. Since then, I've had a lot of questions about Torque and other DMIs and their safety on bermudagrass greens. It's a complex issue, and one that we don't have all of the answers to. Your questions will motivate us to do more research on this next year.

Although many of the newer DMI fungicides on the market are more safe on cool-season putting greens, they can be more injurious on bermudagrass greens. Looking at the graph to the left, you see that applications of Trinity (triticonazole) and Lynx (tebuconazole) caused severe damage to Tifeagle bermudagrass, Bayleton caused a slight reduction in quality, and Banner and Eagle had no effect. This is almost exactly the opposite of what you would see on creeping bentgrass or annual bluegrass putting greens.

Of course, application rate and time of year influence the amount of injury that is caused by DMIs, with the greatest injury caused by high rates, repeated applications, and high temperatures. You will notice that in the above example, we made 5 applications in a row at high label rates during the heat of the summer. No wonder some of them caused injury!

However, don't make the mistake of thinking that that all of the DMIs are safe on the ultradwarfs in the fall and spring or if you're only making one application. As an example, refer to my post from last fall entitled Effects of DMI Fungicides on Bermudagrass Putting Greens. In this example, we saw pretty significant phytotoxicity from some of the DMIs even after one application when temperatures were relatively mild.

I don't mean to scare everyone away from using the DMIs. We never see issues on bermudagrass fairways or athletic fields, and some of the DMIs are perfectly safe on greens. Just choose your products wisely and don't jump on the newest products right away just because they are new!

A New Option for Spring Dead Spot and Fairy Ring Control

Earlier this year, the Cleary Chemical Company released a new fungicide called Torque, which contains the DMI fungicide tebuconazole. More recently, Cleary obtained a 2ee label for the use of Torque for fairy ring prevention. Although it is just another DMI, tebuconazole has some unique properties that should make Torque a very useful product for golf course superintendents.

In particular, we've had a lot of questions about the use of Torque for spring dead spot and fairy ring prevention. Although we have not had the opportunity to evaluate Torque against these diseases, we have a lot of experience with a variety of tebuconazole formulations from other companies.

What we can say is this: tebuconazole is very effective for prevention of both fairy ring and spring dead spot. For spring dead spot, we've seen excellent results in bermudagrass fairways and athletic fields from two applications of tebuconazole, 30 days apart, at the high label rate prior to the onset of dormancy. Unlike Rubigan, which only requires one application in many circumstances, we've found that two applications of tebuconazole are necessary to achieve the best spring dead spot control.

Tebuconazole has also provided excellent prevention of fairy ring caused by puffball-type fungi in sand-based putting greens. Following our standard recommendations, two applications of tebuconazole at the recommended rate on a 30 day interval, beginning when soil temperatures consistently exceed 55F, has been a very effective program.

A note of caution for those with ultradwarf bermudagrasses: we've seen severe injury on the ultradwarfs from tebuconazole, and the Torque label says 'Bermudagrasses can be sensitive to Torque Fungicide under certain conditions'. Until we can get a better feel for the safety of Torque on bermudagrass greens, I would stick with older products that are known to be safe.

Update from the American Phytopathological Meetings

The Midwest is still struggling with heat, humidity and persistent rainfall. As a result, most of the Poa annua in the Midwest is either dead or struggling to say the least. Since I am sitting in the Charlotte airport, I asked Paul Koch for an update on the samples coming into the Turfgrass Diagnostic Lab. It appears that brown patch, Pythium blight and anthracnose are still raging. Our sample numbers are way ahead of last year's entire amount!

It seems that John's post on Monday has caused quite the stir amongst the followers, but he is exactly correct. This is not a "calendar year"! The summer has sucked for most superintendents throughout the US. Grass is dying everywhere and the typical actions like raising the mowing height, alternating mowing and rolling, and other techniques are not helping like we'd like. I think the MOST important thing for golf course superintendents to do is start a line of communication with the owner, membership, golfer, general manager about losing turf. Regardless of the reason or diagnosis this is a banner year for losing turf.

For anyone that knows me I am not a pessimist, but when soil temperatures are above 90 degrees turf is going to have trouble. These temperatures can lead to disease development especially with the amount of rainfall we have had in the Midwest. However, many times grass just dies due to abiotic conditions like poor drainage, anaerobic conditions and heat stress. Remember that annual bluegrass and creeping bentgrass are cool-season grass and prefer to grow when soil temperatures are between 55 and 75 F. Not 90 to 100 F! Lets face it even bermudagrass will struggle when soil temperatures exceed 95 F.

Regarding bacterial wilt, a turfgrass system is a very dynamic biological entity. Many microbes inhabit the rhizosphere of turfgrass plants, which can make turfgrass disease diagnosis extremely difficult. In almost every sample that comes through the TDL, we can find numerous turfgrass pathogens. Furthermore the scientific community is finding that many bacterial species are common epiphytes (live on the surface of leaves) and endophytes (live inside the plant). That being said, it is very common to find bacterial streaming from stressed turfgrass plants. However the signs need to match the symptoms observed in the field and it seems like these two are not jiving.

In my humble opinion, it seems like bacterial wilt has become the perfect fall guy for a brutal summer. It's perfect because it is a mysterious disease with very few effective control measures, but we also have very few control measures for nature.

Summary of a Presentation from APS:

This year's APS meeting was great! Some of the turfgrass pathologist got the opportunity to visit a few golf courses in NC. I was amazed on how quickly I have acclimated to the summers of Wisconsin, damn its hot down there! I really did not have a favorite presentation at this year's meeting. I think the most interesting aspect of the meeting was a special session on Rhizoctonia diseases in turf. There was some fantastic information presented ranging from taxonomic considerations for this genus, biology and management of brown ring patch, management of leaf and sheath spot of ultradwarf bermudagrasses and finally using digital imaging software as a tool to score and identify host resistance in turfgrasses. There was so much information in this session, but the best part was how collegial the speakers were to one another.

Each speaker reference each other and it seemed that they were all working together to help fill in some major gaps with the Rhizoctonia and Rhizoctonia-like diseases in turfgrass. It is cool to be a part of this group, all of my colleagues are extremely helpful and willing to collaborate on projects. As a result, I think we will see many enigmatic problems in turf solved fairly quickly.

Dead Bentgrass Makes Headlines

Well, you know things are rough when the local media is writing about Pythium, aerification, and MiniVerde bermudagrass. Unfortunately that's where we are here in North Carolina and many other parts of the southeast. Check out the following article from last Thursday's Charlotte Observer: 


Hot Weather Turning Putting Greens to Toast


Overall, I think its a pretty accurate description of the struggles that golf courses are facing in the region. I'd be curious to hear everyone's thoughts. There are also a couple of factual errors in the article. I'll give a prize to the first people to point them out by leaving a comment on this post!


A lot of people have been asking about converting their greens to ultradwarf bermudagrasses. They are definitely a good option in certain situations, and several courses in the area have made the switch with great success.


My only advice is this: if you can't maintain good bentgrass greens because of problems with shade, air movement, or soil drainage, then you won't be able to maintain good bermudagrass greens either. The courses that have been most successful in converting to ultradwarfs also removed trees, improved air movement, and corrected drainage problems. Who knows, maybe bentgrass would be doing just fine with these improved growing conditions?

Spring has Sprung!

Well it looks like ol' Jack Frost is slowly shedding his coat in favor of a pair of shades and t-shirts. Spring has been slow in coming, but with 80's on the horizon in the next couple of days it looks like everything is off to the races here. From a disease/stress perspective what does that mean to you in the Southeast? Well, for the warm-season grasses (like bermuda), we should be able to start seeing how bad the winter actually was by starting to see some greening up of the tissue.

Now is the time to start looking at the stolons and stems, to see if color is returning like you see in the image to the right. If the tissue seems dead and brown, it might be time to think about ordering up some sod and/or sprigs. Another disease issue that will start be the impact the winter had on the development of spring dead spot. In Tennessee, we haven't greened up enough yet to see the circular symptoms of the disease (see left image), but with the warm weather that is ahead, it is only a matter of time.

Finally, for those of you managing zoysiagrass, large patch (see image below), caused by Rhizoctonia, will begin to rear its ugly head again. This disease can also attack bermudagrass, but the damage is not usually severe enough to warrant fungicide application (see image far below- that's a large patch!) credit: Adam Nichols, Virginia Tech)

The question of how effective spring applications of fungicides are for large patch is a good one. I don't think we have enough data to conclusively answer the question. Hopefully, you made a few applications in the fall, as that is the best time to apply preventatively.However, if you have an outbreak of large patch that is actively growing, fungicide applications might be warranted to at least reduce the spread of the disease.

Our junior-year turfgrass students are setting off on their internships for the summer, so I will be posting much more frequently now that teaching is on hiatus for awhile. So I am off to start looking for large patch in my trials, but the difference is I get excited when I have a bunch of it, and it is uniformly distributed over my plots!

Stay tuned for the next couple of weeks as we look at what spring has for cool-season diseases/stresses next week, and the following week, what we need to start thinking about for summer (which will be here before we know it!).

Brrrrrrrrrr......Allow me to introduce myself

For those of you following Lane Tredway on the Turfgrass Disease Blog, I hate to disappoint you, but I will be guest hosting while Lane is off traipsing across the continents in search of those elusive turf pathogens. My name is Brandon Horvath, and I am a professor at the University of Tennessee in Knoxville. I was previously at Virginia Tech and located down in the Virginia Beach area, so I have been calling the transition zone my home for the last 5 years. In all seriousness, Lane will be making posts as an international blogger, since he is on his well-deserved sabbatical, and we here at the Turfgrass Disease Blog wish him safe travels.

So, I found myself wondering what I would discuss for my first post, and it looks like Mother Nature has decided for me: Wow! It's been really cold! I was in Michigan prior to moving down South, so the cold here is not too bad, but as my 4 year old, Alex, likes to say, "Daddy, its super, super, super, super, cold out!" That's kind of what I would like to think the bermudagrasses (esp. ultradwarfs) have been saying too, especially if you're in a situation where covering is a labor-limited situation and might not have been able to put the covers on fast enough. Here in Knoxville, the temperatures have hovered for the last couple of weeks with highs in the low-mid thirties, and lows in the teens. The real question that I am sure is not lost on many of you dealing with these conditions is, "Will my turf be alive in the spring?" The short answer is that we don't know enough to predict with a high degree of accuracy how bermudagrasses handle the cold. The newer varieties with improved cold tolerance (Riviera, Yukon, Patriot, etc.) haven't really seen much of these kinds of conditions since their introduction to the market, so it will be interesting to see how they fare next to standbys like 419 and Tifsport. The ultradwarfs (TifEagle, Champion, Mini-Verde, etc.) have moved somewhat North since the last major cold winter, so that will be interesting to observe too. I suspect that the really wet, soggy conditions at the end of the season, and the cold snaps we have had this winter are going to make for some pretty poor bermudagrass conditions this spring when it comes out of dormancy.

Many of you are probably already thinking, "So, how do I know how bad it will be, and can I do anything about it?" One of the easiest things you can do over the next couple of months will be to collect a few samples from turf areas you are worried about (e.g. shady areas on a fairway, low spots that collect water, etc.) and a few samples from areas that consistently perform well (e.g. well-drained areas, full sun, etc.) and begin to bring them inside and acclimate them to warmer conditions. The first step would be to bring them into an unheated, cold area sheltered from the elements in the maintenance facility. After a few days of slightly warmer temps, move them to an area that is warmer, but still cool (e.g. heated equipment storage areas). Following a few days, move them into a warmer area yet, and finally into an area in the shop that is warm enough that the plants (if alive) will begin to green up. You will need to keep them watered, not saturated, and monitor them for growth. Doing this every couple of weeks over the next few months will give you a good idea whether you will need to reserve some sod or sprigs for re-establishment or if those nightmares you had about whole fairways being dead was really just a bad dream. The important thing is to remember that by having some advanced warning of what you might be in store for will help you prepare your membership prior to any damage, and this will be a silver lining in an otherwise dark cloud.

I am looking forward to posting regularly on the blog, and look forward to hearing from many of you about problems and questions you might have as we tackle what's in store for 2010!