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.

Turf video fun, dollar spot in zoysia, hammock accidents, and more!

Two turf videos:

Larry Stowell and Wendy Gelerntner from Pace (http://www.paceturf.org/) have posted a few videos of turf topics on their new Facebook page.

Here’s a 3-minute demo of fairy ring diagnosis:

http://www.facebook.com/video/video.php?v=1469235847572

And, for fun, a 1-minute clip of a field trial. It uses time-lapse and is pretty cool:

http://www.facebook.com/video/video.php?v=1466904469289

Even more videos!

Syngenta has produced a series of short videos that explains how to take an active ingredient and turn it into a product that is safe to plants, stores well, does not clog equipment, etc.

You can find the video clips HERE

I don’t mean this to be an ad for Syngenta products–it’s just a user-friendly way to learn a little bit about formulations.

Section #3 is the most in depth, about 7 minutes, and discusses how companies use surfactants, dispersants, buffers, adjuvants, etc, to turn a gooey, hydrophobic raw active ingredient into something that can be put in a spray tank and applied to plants.

Dollar spot

The fairway-height zoysia at our turf research center was looking “speckled” this morning.

With a closer look, it appears that dollar spot is present. It is not very common on zoysiagrass here in Kansas, but it occurs from time to time.

Brown patch is also visible in creeping bent plots where it was not present just 2 days ago:

Growth Regulating effects:

The outlined plot is being treated every 14 days with a product that contains the DMI fungicide propiconazole. DMI products can have undesirable growth regulating effects.

Dr. Lane Tredway described DMI effects here:

http://turfdiseases.blogspot.com/2009/06/beware-dmi-fungicides.html

Dr. K visits Dr. K

I was in my hometown of Madison, WI, over the holiday weekend to visit family. Beautiful weather, good family time, fireworks, Mom and Dad’s cooking… Other than falling out of a hammock and hurting my wrist, which I then aggravated by competing with my brothers in a “crabwalking race” across the backyard, it couldn’t have been better.

While there, I stopped in at the University of Wisconsin-Madison turf research facility, the O. J. Noer Turfgrass Research and Education Facility. You can find a link to it HERE.

Dr. Jim Kerns gave me a tour. At “the Noer,” as it is called, there are a variety of studies going on this year.

Mowing height physiology:

Alternative turfgrass species (such as Junegrass, which is native here in Kansas) for reduced inputs (water, for example).

Shade:

Phosphorus fertility:

On the disease side, they are looking at snow molds, dollar spot, Pythium, and brown patch. There was a fair amount of dollar spot that day, but somehow I did not manage to get a photo of it. I guess I was too distracted by all the disease.

For me it was interesting to see their set-up, how they organize the field trials, etc. We have some similar interests–disease management, fertility, water use, overall reduction of inputs, etc. It’s always good to get out and see how other people approach things.

Showing off my hometown:

Get Yer T-T's Out! (and use them for summer disease control)

¡Anthracnose Está Aquí!
I just got back to Washington DC from California where I had a great time at the GCSA of Southern California's Annual Scholarship and Research Tournament (more about that next week though!).

This week, we started to get a good number of anthracnose samples on both annual bluegrass and creeping bentgrass at UCR. It's a little early for full blown anthracnose season, but keep your eyes out for the disease; especially on annual bluegrass putting greens. Apply adequate nitrogen, keep on top of your sand topdressing, and start your preventive fungicide programs if you already haven't started.

Other diseases worth mentioning would be fairy ring and southern blight (Sclerotium rolfsii); both of these diseases seem to be active in California right now (seen, reported or diganosed), including right on top of my dollar spot experiment at UCR (damn it).

New DMI-Fungicides for Summer Disease Control on Cool-season Turf
'T-T's? Yeah, I know, it’s a bad pun, but I just wanted to give a quick update (and possibly clear up some confusion) on some new DMI-fungicides on the market that oddly all have 'T' in the name and could be useful for summer disease management, focusing on their utility on diseases of cool season turf. Trinity (BASF), Triton (Bayer), Tourney (Valent) and Torque (Cleary Chemical) are all new DMI-fungicides that are or will soon be registered for use for turfgrass control in the U.S.

All DMI-fungicides work by interfering with fungal cell membrane biosynthesis; specifically by interfering with demethylation of an ergosterol precursor (don't let me geek out on you guys here). Because of this extra methyl-group sticking out of the ergosterol, the cell membranes in fungi don't assemble together properly and voilà, the fungal membranes break open and the fungus dies.



You can see this in the pictures above (via Bayer Crop Science) of the untreated (top) and DMI-treated fungi (bottom).

Oomycetes like Pythium and downy mildews, don't use ergosterol in their cell membranes, so while DMIs are pretty broad spectrum against most major turfgrass diseases like dollar spot, brown patch and anthracnose, they won't touch oomycetes.

Like all other DMIs (Banner MAXX, Bayleton, Eagle, Rubigan), these new fungicides are systemic (acropetal penetrants) and have significant post-infection activity vs. fungi. Although I'm talking about these new 'T' named DMIs – remember that each of the DMIs is unique and some work better than other vs. certain diseases, and I'm not necessarily saying you should throw out your old ones in favor of these new fungicides!

Also – just a reminder, DMIs also tend to cause some injury on turf when used at high rates or repeatedly, so be careful when using these and stick to the label recommendations. Of special consideration is using these on warm season turf, on annual bluegrass putting greens and in combination with plant growth regulators. I'm not pointing fingers at anybody, but read up on the label just to save yourself any unnecessary summer grief when using DMIs.

* Check with your local distributor or manufacturer representative on availability for these products; my first hand experience with these comes from California, and as you know California and New York are typically the last places for new pesticides to get state registration and approval.

Trinity Fungicide (active ingredient: triticonazole)
BASF's Trinity fungicide has been registered in a number of states and recently received a California registration. It comes as a liquid containing 1.69 lb of triticonazole per gallon of product and use rates go from 0.5 to 2 fl oz per 1,000 sq ft (limited to 1 fl oz in California) and the fungicide controls many of the major turf summer diseases such as dollar spot, anthracnose, brown patch and summer patch. Trinity also has good activity vs. brown ring patch (aka Waitea patch), and is labeled for suppression of algae, which can use useful for the control of this problem on putting greens. See http://betterturf.basf.us/ for more info on Trinity.

Chipco Triton Flo and Triton (active ingredient: triticonazole)
Bayer Environmental Science's Triton fungicides share the same active ingredient as BASF's Trinity but differ in their formulations. Chipco Triton Flo is a liquid containing 3.1 lb of triticonazole per gallon (thus lower labeled use rates as compared to Trinity) and is formulated with Bayer's StressGard pigment (which is an added bonus for cool season turf in the summer). Chipco Triton Flo use rates go from 0.28 to 1.1 fl oz per 1,000 sq ft. On the other hand, Triton comes in a dry formulation containing 70% triticonazole (use rates of 0.15 to 0.6 oz per 1,000 sq ft) and does not contain the StressGard pigment. Both fungicides control summer diseases like dollar spot, anthracnose, brown patch and summer patch as well as brown ring patch (and have algae suppression on the label). Currently, the Triton label is broader than the Chipco Triton Flo label but I expect that to change as Chipco Triton Flo nears registration throughout the U.S. It's not clear to me if Bayer intends to have both fungicide formulations on the market at the same time or if the pigmented form with StressGard will phase out the non-pigmented one. See http://www.backedbybayer.com for more information on Triton and Chipco Triton Flo

Tourney Fungicide (active ingredient: metconazole)
Valent Professional Products Tourney is now labeled in most of the U.S. including California and New York. It comes as a dry formulation containing 50% metconazole, and has use rates of 0.18 to 0.44 oz per 1,000 sq ft. Like the previous fungicides discussed above, Tourney is effective vs. dollar spot, anthracnose, brown patch, summer patch and brown ring patch, but has a slightly more expansive label that includes summer trouble makers such as fairy ring and gray leaf spot. See http://www.valent.com/professional/index.cfm for more info on Tourney.

Torque Fungicide (active ingredient: tebuconazole)
Cleary Chemical recently secured tebuconazole for use for turf disease management. For a long time, you could buy it in the home and garden section of your local hardware store for lawn disease control, but previous attempts to get it registered for professional use through the EPA were 'difficult' at best. Torque comes as a liquid containing 3.6 lbs tebuconazole per gallon and is labeled for use at 0.6 fl oz per 1,000 sq ft. The label includes summer diseases such as dollar spot, anthracnose, brown patch, summer patch and gray leaf spot and is effective vs. brown ring patch. Registration is limited for now to just 26 states that includes Washington and Oregon in the West (but not California, Arizona, Nevada, Hawaii or most of the other states west of the Rockies. I would note that our research at UCR showed that tebuconazole and propiconazole (Banner MAXX) were the most intrinsically active vs. anthracnose, making these two very useful DMIs vs. this disease. See http://www.clearychemical.com for more info on Torque.

I'd really like to hear some feedback from you guys on how these new DMIs (and older ones) are working for you now or how they worked for you last year. Lemme know what you think!

Signing off from the right coast until next week.....

Effects of DMI Fungicides on Bermudagrass Putting Greens

Those of you that follow this blog know that I am not a big fan of using DMI fungicides on creeping bentgrass and annual bluegrass putting greens during the heat of summer. The impacts of these fungicides on bermudagrass greens, however, are not as well understood. Some of the newer DMIs, like Trinity, Triton and Tourney, are not labeled for application to ultradwarf bermudagrass varieties. Even though these products are safer on the cool-season grasses, they can cause severe phytotoxicity and thinning of 'Champion', 'Tifeagle' and 'Miniverde' greens.

A recent trial we performed on 'Champion' bermudagrass in Rocky Mount, NC showed some unexpected results. Each fungicide was applied once, on August 20, the day after the greens were hollow-tine aerified and topdressed. The plots were evaluated for phytotoxicity, turf quality, and recovery from aerification on September 1.

Not surprisingly, plots treated with Trinity, Tourney, and Triton FLO exhibited significant phytotoxicity and reduced turf quality as compared to the untreated control. Banner and Bayleton had similar effects, just not as severe as the others.

What was unexpected was the effect of the DMIs on recovery from aerification, as measured by the number of aerification holes still visible on Sept 1. Plots treated with Trinity, Tourney, and Triton FLO recovered almost as quickly as the untreated plots, whereas both Bayleton and Banner dramatically slowed recovery, especially Banner.

So, the take home message is, even though Bayleton and Banner are labeled for application to bermudagrass greens, these products can have adverse affects on the turf, in this case, slower recovery from aerification. More research is needed to fully characterize the effects of the DMIs on bermudagrass greens. In the meantime, I'd recommend avoiding applications of DMI fungicides either before or after hollow-tine aerification practices.

Beware of the DMI Fungicides

As temperatures climb in the southeast US, it is time to put the DMI fungicides on the shelf until fall. All of them.

The DMIs can cause significant damage to bentgrass and bermudagrass putting greens if temperatures exceed 90 degrees after an application is made. Note that the temperature at the time of application is not important, it is the weather in the days and weeks after an application that leads to problems.

The DMI fungicides include Banner, Bayleton, Eagle, Rubigan, Tourney, Trinity, and Triton.

All of the DMIs have growth regulating properties. The effects are minimal when the turf is healthy and actively growing, but significant thinning of the canopy can occur during hot weather, even on otherwise healthy turf. Combine a DMI application, hot weather, and severely stressed turf and the consequences can be disastrous.

Several new DMI fungicides have been released in the last two years, and many of them are promoted as "safe". Admittedly, they are safer, but by no means are they safe. Severe damage has been observed where these new DMIs were applied to stressed cool-season grasses prior to or during hot weather. We have also observed that these new DMIs are more injurious to bermudagrass than the older DMIs. Tourney, Trinity, and Triton are not labeled for application to bermudagrass greens for this reason.

Most golf course superintendents in the southeast don't need DMIs during the summer anyway. Effective alternatives are available for control of most diseases, but anthracnose is an exception. Many superintendents with older bentgrass varieties or Poa annua greens battle this disease, and most anthracnose populations have become resistant to the QoI and benzimidazole fungicides. If you are in this situation, you pretty much have to use a DMI. The newer DMIs (Tourney, Trinity, and Triton) are very effective against anthracnose and should be worked into a preventative anthracnose program. Just be sure to use low rates, tank-mix with chlorothalonil to prevent algae invasion, and do not apply more than once a month to minimize the potential for injury.

It's not too late to prevent fairy ring and Pythium root dysfunction

If you haven't made your preventative fungicide applications for fairy ring and Pythium root dysfunction yet, it's not too late, but it will be very soon.

Although symptoms of these diseases are most common during the heat of summer, we've found that the pathogens are most active during the spring and early summer. Fungicides are most effective when applied during these periods of pathogen activity.

Pythium root dysfunction is a common problem in the southeast on creeping bentgrass putting greens built within the last 10 years. The pathogen infects the roots during the fall, winter, and spring when soil temperatures are between 50 and 75 degrees.

Remember that Pythium root dysfunction is a stress-induced disease. Low nitrogen inputs (less than 3 lbs per year), drought stress, close mowing, and infrequent aerification are common sources of stress that compound the disease. Maintaining a healthy turf plant with sound agronomic practices goes a long way towards reducing problems. All the fungicides in the world will not provide acceptable control of PRD if the turf is continuously stressed.

Preventive fungicide applications should be made in the fall, winter, and spring when average daily soil temperatures between 50 and 75 degrees. For details on recommended fungicide rotations, please refer to our information sheet on TurfFiles. Remember that fungicides should be watered into the soil right away for best results.

We've made excellent progress in fairy ring management over the last 5 years. The DMI fungicides, such as Bayleton, Eagle, Tourney, Trinity, and Triton, have been providing excellent control in the southeastern United States. For best results, these products should be applied when 5-day average soil temperatures are between 55 and 65 degrees. However, as long as they are applied before symptoms appear, they will provide good control in our experience.

Just like with PRD, fungicides must be applied to the soil for best results. Applications should be watered-in as soon as possible with 1/8" to 1/4" of irrigation. We do not recommend tank-mixing the DMIs with wetting agents or soil surfactants, as we've observed reduced control from these combinations. Wetting agents should be applied separately as part of your normal program.

For more information on fairy ring prevention, please refer to the Fairy Ring Disease Profile on TurfFiles.