Why They Call it the Transition Zone

Spring dead spot of bermudagrass

As the old joke goes, "In the transition zone, we can grow all of the turfgrasses, we just can't grow any of them well".

The last year has been an excellent demonstration of this fact. Spring 2010 brought major problems with winter-kill in the warm-season grasses across much of the southeast. Everyone will remember the summer of 2010 as the year when record heat caused widespread failure of creeping bentgrass putting greens. 

Large patch of bermudagrass

The spring of 2011 hasn't been much kinder. Spring dead spot is particularly severe on bermudagrass this spring, and I've heard several reports of control failures from preventive fungicide applications. We've seen an unusual number of cases of spring dead spot on zoysiagrass as well (more on that next week).

Large patch (aka zoysia patch, aka brown patch, aka large brown patch....did I miss any? Seriously, can't we all just call it large patch?) is raging on all of the warm-season grasses as well. This spring is the first time I've seen large patch cause significant damage to bermudagrass in the Raleigh area. Zoysiagrass, St. Augustinegrass, and centipedegrass are affected very severely as well.

Many people struggle with these diseases of warm-season grasses because they have to be treated long before the symptoms express themselves. It is easy to forget about spring dead spot and large patch in the fall when everything is looking good. 

In addition, the economic downturn has led to severe budget cuts at many facilities, and the poor warm-season grasses are usually the ones that are left to fend for themselves without fungicide protection.

Over the next few weeks, I'll be writing in more detail about spring dead spot and large patch in the warm-season grasses. We'll cover things you can do now and during the growing season to help manage these diseases and how to prepare for preventive fungicide applications this fall. Stay tuned!

Fungicide Programs: Take this short survey and win!

Please help us to help you better!

We designed a short, 5 minute survey to better understand how golf course superintendents build and implement their putting green fungicide programs. Your valuable responses will be used to guide our future efforts to develop online tools and utilities for golf course turfgrasses.

One lucky participant will be selected at random to receive 2 free sample diagnoses from the NC State Turf Diagnostics Lab, a $200 value. But you must take the survey by March 21 to be eligible to win, so don't delay!

Click here to take survey

Thank you in advance for your assistance on this project!

Practical Guide to Turfgrass Fungicides (new book)

The arrival of Dr. Latin's new fungicide book for the turfgrass industry has been highly anticipated and was basically unveiled at the Golf Industry Show last week. I was fortunate enough to get a copy of the book from the bookstore before copies ran out and even more fortunate to have Dr. Latin sign a copy (although I interrupted an interview he was having with a potential grad student to get it). As with any profession, continued education is a must and this is definitely one book that you want to have on your shelf. You can purchase your copy at the APS website. The book is currently on sale for $119.95 and although it's not cheap, someone has to support Dr. Latin's golf habit it is well worth the price.


Here is some information about the book from the American Phytopathological Society (the book's publisher):

Contents

• Turf Fungicide Fundamentals
• Modes of Action of Fungicides
• Fungicide Resistance
• Factors That Influence Fungicide Performance
• Biofungicides, Phosphonates, and Post-Patent Products
• Fungicide Interactions
• Scheduling Fungicides for Turf Disease Control
• Fungicide Regulation
• Interpreting Fungicide Performance Research
• Turf Disease Characteristics and Control
• Turf Fungicide Profiles
• Index

Delivers Proven Strategies for Turf Fungicide Management

• Provides turf managers with a sound foundation and understanding of how and why fungicides work by explaining how they move within the plant (phytomobility) and how they stop fungal growth (mode of action)
• Explains how to integrate disease-control chemicals with essential management practices and shows how a variety of plant, pathogen, and environmental factors can influence fungicide performance.
• Describes different approaches to scheduling fungicide applications—based on damage thresholds, days between sprays, and environmental conditions—explaining the advantages and disadvantages of each approach and enabling development of effective strategies and tactics for disease control.
• Supplies a single source for accurate, current descriptions and control recommendations for more than two dozen damaging turf diseases caused by fungi.
• Separates anecdotal fungicide selection information from valid research results and explains how to interpret research reports using examples describing the effectiveness of fungicide products.

To the right is my copy signed by the Great Doctor!

Is Emerald a Poor Curative for Dollar Spot?

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.

Civitas Update....By Popular Demand

First, my apologies for the tardiness of this post. The pre-Thanksgiving travel crunch got the best of me last week, and of course I spent the entire weekend watching football and hockey, so I am just now getting caught up! Several people have asked what happened to the Civitas update, so here it is:

Civitas is a new product for disease and insect control in turfgrasses that was developed by Suncor, formerly known as PetroCanada. The active ingredient is mineral oil, otherwise known as 'horticultural oil', which has been used for management of plant pests for many years. It has just never been used in turf because of issues with phytotoxicity. However, Suncor developed a pigment product, called Harmonizer, that is mixed with Civitas to reduce the potential for phytotoxicity. The advantage of mineral oil as a fungicide is that it has very low environmental impacts due to its low toxicity and rapid breakdown in the environment.

Because it contains oil and pigment, Civitas has a very noticeable effect on the color and appearance of the turf. The Harmonizer pigment, depending on the application rate, is a very dark green, similar to that provided by an application of Triton Flo or Tartan. Some people have complained that transfer of the pigment to shoes and clothing has been a problem, but I haven't rolled around on our research plots yet to see how big of a problem that is.

The mineral oil component of Civitas also gives the turf a distinct greasy appearance, very similar to that caused by an application of a wetting agent like Cascade. This greasy appearance is most evident in the morning and persists for several days to a week after application. Because of these unique characteristics of Civitas, I suggest that people try it out on a nursery green or putting green before treating the whole course with it.

We've been evaluating Civitas for control of various turf diseases for three years now. For a summary of our previous results, please see my post from last year entitled Civitas shows promise for control of dollar spot and brown patch. Be sure to read the comments at the bottom provided by Wakar Uddin, Bruce Clarke, and others regarding their experiences with Civitas.

We continue to see similar results against dollar spot and brown patch in our trials. However, this year we ran into serious problems with phytotoxicity when Civitas and Harmonizer was tank-mixed with Daconil and Banner Maxx. The injury appeared very quickly after the first application in May and became more severe as time went on. As you can see in the graph to the left, it is also interesting to note that half rates of the mixture components did not reduce the amount of phytotoxicity observed. Based on this result, we definitely recommend that Civitas and Harmonizer should not be mixed with Daconil and Banner, or with other fungicides until we have the opportunity to evaluate more mixtures for their safety.

We haven't seen significant phytotoxicity from applications of Civitas and Harmonizer alone in our trials, but some users have reported injury during times of severe stress, with high temperatures consistently above 90F. It makes sense that it could create problems to coat the turf leaves in oil under these types of conditions.

To summarize, Civitas has good activity against several important turf diseases like dollar spot, brown patch, anthracnose, and leaf spot diseases. Although it does not provide acceptable control alone in most cases, my opinion is that it could be useful as part of a disease control program. Civitas and Harmonizer should not be mixed with other fungicides or applied to severely stressed turf, or severe injury could result. However, if you are interested in using products that pose less risk to environment, then Civitas is a good choice.

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.

Conference Season and why I choose Houston when flying west...

Well, like the others (Megan, call sign 'Wraith'- see this site, Frank, call sign 'Yankee', Jim, call sign 'Yoda', and John, call sign 'Weasel') conference season has been in full swing. I attended the North Carolina Turfgrass Conference in Show a couple of weeks ago and had a great time sharing information about fungicide programming with the superintendents in NC. The faculty and staff at NCSU were extremely hospitable and I enjoyed my visit there. Last week I was in San Diego like the everyone else to work with our students on the Turf Bowl Challenge, and to work with the cooperators from the various agrochemical companies that conduct research with us. It was a good show, and I am looking forward to spring arriving.

I thought I would also share with you some of the questions that came up during my visit in NC on fungicide programming. The main concern had to do with budgetary restrictions, and that is something we have seen all over these days. Rather than starting with the 'kid @ the concession stand' approach of "how much can I buy for this much?", I would suggest building a fungicide program as if you didn't have a budget. This way will allow you to start with a top program, and then whittle away at the edges of the program and make small changes that can save you dollars, but doesn't impact the integrity of the program. The key to doing this is to make sure you first identify the major priorities that you want the program to cover. For most growing bentgrass, that would be Pythium, dollar spot, and brown patch. If you are managing Poa annua those priorities will shift slightly, and you will be focused on dollar spot, crown rotting anthracnose, and summer patch. Finally, if bermuda is the grass of choice, spring dead spot, Rhizoctonia leaf and sheath blight (a.k.a. mini-ring), and perhaps dollar spot might be issues. The key is for you to identify your priorities and build a top-shelf program that fits. Doing this, it is pretty easy to identify some treatments that you can adjust/remove and save 15-20% of the cost of the top-shelf program. Further cuts should be focused around the times of year where disease isn't a major concern, and cultural controls might have more impact. One of the questions that is popping up more frequently is the "rambo" or pitting dollar spot. I believe that this type of symptom is often seen where N fertility has been drastically reduced either because of greenspeed concerns, or budgetary restrictions. Remember that a healthy plant with adequate N fertility will allow the fungicides you do apply to work better and longer than plants that are N starved.

The last item that I notice with regard to programming, is the doubling up of fungicide applications. This happens particularly frequently with the phosphite class of chemistry. I have had several superintendents describe their programs to me, and frequently there are multiple phosphite products in there for different reasons. Look through your program and make sure you aren't doubling up resources. Use fungicide combinations that make sense to target the diseases that are a priority, and these strategies can help save another 5-10%.

Now- for the second part of my title; Why I choose Houston when flying west in the winter. Wikipedia sums it up best:

Houston:

"Snow is unusual in Houston, with an event occurring nearly every 4 years. Snow has fallen ap

proximately 30 times since 1895,^[17] more recently on December 4, 2009.^[18] Freezing rain events, also known as ice storms, can be detrimental to local traffic, and can close schools and businesses. The most recent ice storms occurred in 1997 and 2007."

Atlanta:

"An average year sees frost on 36 days; snowfall averages about 2 inches (5 cm) annually. The heaviest single storm brought 10 inches (25 cm) on January 23, 1940.^[45] Blizzards are rare but possible; one hit in March 1993. Frequent ice storms can cause more problems than snow; the most severe such storm may have occurred on January 7, 1973.^[46]"

While I don't do too much betting (I do like blackjack), I like my chances in a place where on average a snow event occurs once every 4 years versus annual snowfall totaling 2 inches. I had little trouble getting back- but there was some excitement on my return trip to Knoxville. Continental had to move a pilot to Knoxville to fly a plane, but our plane was full (b/c of weather, etc.). So, they bumped a paying, ticket-holding customer in favor of their employee. On the surface this seemed to be a poor choice, but as I thought about it, it occurred to me that is was probably better to inconvenience a single person, than to have to cancel another flight due to the lack of a pilot. Travel delays suck, no doubt, but when it happens try to remember that you will get a lot farther with a smile, than by being demanding- one of the bumped passengers buddies was asked to leave after throwing a tirade and being disrespectful to the flight crew...

and as for my call sign- 'Cajun', I think I like that one...

Over and out!

Prevention of Pythium Root Dysfunction in Bentgrass Greens

For golf course superintendents who've struggled with Pythium root dysfunction in the past, now is the ideal time to initiate a preventive fungicide program. Pythium volutum, the most common PRD pathogen in our experience, starts to actively infect bentgrass roots in the fall when soil temperatures consistently dip below 75 degrees. That, combined with plenty of moisture throughout the Southeast, means that the pathogen is almost certainly active now.

Not very many products are effective against PRD. Even though it is caused by a Pythium, some of the standard Pythium fungicides like mefanoxam, propamocarb, ethazole, and fosetyl-Al are not very effective when applied alone.

Instead, the QoI and Qii fungicides have been most effective against PRD in our trials. The QoI fungicide Insignia (0.9 oz) has historically been the most effective product. We have also seen good control from Heritage TL (2 fl oz) and Compass (0.25 oz) but only on a preventive basis.

The QiI class of chemistry is relatively new, and there is currently only one product available in this category: Segway, which contains the active ingredient cyazofamid. Applications of this product at 0.9 fl oz per 1000 sq ft have also provided very good control of PRD. Segway is an important addition to our arsenal against PRD because it gives us another chemical class to rotate with to prevent the development of fungicide resistance in Pythium volutum.

Tank-mixtures of fosetyl-Al + propamocarb (Signature, 4 oz + Banol, 2 fl oz, for example) and fosetyl-Al + mefanoxam (Signature, 4 oz + Subdue Maxx, 1 fl oz, for example) have provided good control in our trials or based on superintendents' observations. These tank-mixtures, although expensive, should also be worked into your program to help prevent fungicide resistance.

As mentioned above, a preventive program should be initiated in the fall when soil temperatures consistently dip below 75 degrees. Repeat applications on 21 to 28 day intervals as long as soil temperatures are between 50 and 75 degrees are recommended where PRD has been a persistent problem. Less frequent applications may be sufficient where the disease has only been a minor problem or where growing/management conditions are less stressful during the summer. Since PRD is a stress-induced disease, there is no "one size fits all" fungicide program to control it.

Note that applications of Insignia and Segway should be watered into the soil immediately to drive the fungicide into the root zone. Approximately 0.125" of irrigation has worked well in our trials. Since fosetyl-Al moves downward in the plant, tank.mixtures including this product should be left to dry on the foliage for best results.

Large patch is brewing in the warm-season grasses

With cool, wet weather setting in across much of the southeast, now is the time to initiate a preventive fungicide program for large patch on the warm-season grasses. Zoysiagrass, centipedegrass, and St. Augustinegrass are most prone to this disease; large patch rarely causes significant damage to bermudagrass turf. Not all turf needs to be treated with fungicides to control large patch, but areas that have sustained severe damage in the past should be sprayed on a preventive basis.

One great advantage of the warm-season grasses is that they are fairly resistant to diseases; in most parts of the southeast, we only need to worry about one or two diseases on these grasses. Spring dead spot is a major problem on bermudagrass, and large patch can cause severe problems on all the others - zoysiagrass, centipedegrass, and St. Augustinegrass.

One problem with large patch is that it comes at a time when the warm-season grasses are shutting down for the winter or greening-up in the early spring. As a result, the potential for recovery once symptoms appear is slim to none. Once an outbreak occurs, you're probably going to be looking at those symptoms until April or May when the turf really starts growing again.

The other problem with large patch is that the appearance of symptoms is very unpredictable. Sometimes they appear in late summer, other times during the fall, and in many cases no symptoms are observed in the spring. So how are you supposed to prevent the symptoms if you don't know when they are going to appear?

The answer is easy - don't time your fungicide applications based on when symptoms have appeared in the past. Instead, you should time applications based on when the pathogen is active. As it turns out, we know that the large patch pathogen becomes active when soil temperatures consistently dip below 70 degrees at the 1 to 2 inch depth. In other words, NOW IS THE TIME TO START PREVENTIVE PROGRAMS FOR LARGE PATCH IN MANY AREAS!

There has been much confusion over the name of this disease, and as a result, very few fungicides are specifically for 'large patch'. Some labels still refer to the disease as 'brown patch', whereas others call it 'zoysia patch'. Since they are all caused by Rhizoctonia solani, any fungicide that has one of these diseases on the label can be used for large patch control.

In some cases, one well-timed fungicide application in the fall can provide season long control of large patch. However, in severely affected sites, where disease pressure is high, repeated applications are often necessary. Two applications in the fall, 4 to 6 weeks apart, and one application in the spring when the turf is nearing full green-up is the ideal program. If three applications are not possible financially, the fall applications are probably more important than the spring application.

Strong brown patch fungicides like Heritage (0.4 oz of 50WG or 2 fl oz of TL), Insignia (0.9 oz) and ProStar (2.2 oz) are very effective for large patch control. Some of the DMI fungicides, Bayleton (1 oz) in particular, have performed very well also. Recent trials have also shown that Headway (3 fl oz), a pre-mix of Heritage and Banner, is a very effective large patch fungicide.

For more information about large patch management with fungicides and cultural practices, please refer to our Large Patch Disease Profile on TurfFiles.

Red Leaf Spot Active...

Disease activity has basically gotten to a point of boredom for many of us who like to see new and exciting diseases. Dollar spot continues to be the number one problem in the Northeastern United States and this is not much of a departure from the past few weeks or so. Temperatures are finally getting cooler at night, but the forecast for some areas have temperatures reaching into the 80's again this week.

Much of the effort in terms of turfgrass management has shifted towards the necessary cultural practices needed to ensure healthy turf heading into the winter and also coming out of spring. Snow mold applications are still a couple of months away, but superintendents would be wise to check out some of the posts from Dr. Kerns in the Midwest region where he experiences some of the highest snow mold pressures around.

For me, last week was fairly exciting (although not exciting enough to come up with another PlayTurf cover) as some of our plots unexpectedly developed red leaf spot. While at Maryland, we heard a lot of buzz from superintendents in the field who felt that they were dealing with red leaf spot. However, upon further inspection we almost always found the disease to be late cases of Microdochium patch (aka, Pink snow mold or Fusarium patch) occuring during overcast weather. This caused some controversy to the point of almost having a manuscript rejected because the editors suggested that we did not probably identify Microdochium patch (the disease was rated in the first week of June in Maryland...which was highly unusual). I assured the editors that I was a major advocate of the cereal Lucky Charms and could easily distinguish my "crescent moon shapes" (typical of Microdochium) from that of a cigar (typical shape of the Dreschlera genus that causes red leaf spot).

Anyway, the real first time that I even saw red leaf spot was at the research plots at my first University of Massachusetts field day. I took out the trusty pocket knife and took a small sample back to the lab at UConn and sure enough...red leaf spot (sorry for whose ever plots those were...I only took a small piece). In reviewing the latest turfgrass fungicide updates from the University of Kentucky, the reports from Paul Vincelli generally hold true with the data collected from the unexpected disease in our plots. Our data suggest that the QoI fungicides held up equally well (Disarm did seem to provide slightly less control, but this was not significant). Although ProStar did not enhance disease activity in our plots as suggested by Dr. Vincelli, it definitely did not provide any suppression. Two surprises in the data relative to past trials were that myclobutanil (Quali-Pro) seemed to provide excellent preventive suppression AND that Emerald (which is only good for dollar spot and bentgrass dead spot) seemed to provide a moderate level of suppression of the disease.

Since this is my first time seeing data on red leaf spot in my own plots, please feel free to comment on your thoughts about the disease in trials conducted in your region. As with Jim's post last week about the lack of control with Curalan for early season dollar spot, we may continue to see differences in control of certain diseases based on these geographic regions.

Spring Dead Spot Control in Hybrid Bermudagrass

Spring seems like a long way off, but now is the time to prevent your bermudagrass turf from looking like this upon greenup in the spring. Spring dead spot, caused by Ophiosphaerella korrae, can cause severe and long-term damage to bermudagrass on greens, fairways, roughs, athletic fields, and highly maintained landscapes if it is not properly managed.

There are many things that can be done to help reduce spring dead spot development. Probably one of the most effective practices is hollow-tine aerification. In the picture to the right, look how severe the disease is on the recreational area to the right as compared to the soccer field on the left. What's the difference? The soccer field was hollow-tine aerified three times in the previous year, whereas the surrounding areas were not.

In the Eastern United States, most people have good success in controlling spring dead spot with 1 or 2 fungicide applications in the fall. We've found that these applications are most effective when average daily soil temperatures are below 80 degrees and above 60 degrees.

The Midwest is a completely different story, however, as fungicides generally don't work very well against spring dead spot in that part of the country. Some have theorized this is because spring dead spot is actually caused by a different pathogen in the Midwest, where Ophioshpaerella herpotricha is most widespread. However, we've had great success in controlling O. herpotricha with fungicides in North Carolina in the few locations where it is present, so I tend to believe that different soil properties are responsible for the control difficulties observed in certain regions. Just keep in mind that what we find to work best in the Southeast isn't guaranteed to work everywhere.

Over the last 8 years, Rubigan has been the most effective and consistent fungicide for spring dead spot control in our trials. In fairways and athletic fields, we have seen excellent control from 2 applications (30 days apart) at 4 fl oz/1000 ft sq or a single application at 6 fl oz/1000 ft sq. On putting greens, which tend to be more susceptible to spring dead spot, I would recommend a total of 12 fl oz/1000 ft sq applied as either three 4 fl oz applications or two 6 fl oz applications.

Regardless of the program that you select, is critical that all of the applications are made before average daily soil temperatures dip below 60 degrees. This is the point at which bermudagrass plants start to shut down, and after this point the fungicide will not be absorbed and translocated in the plant.

There are other options for spring dead spot control. While Rubigan has been most consistent in our studies across a number of locations, we have also seen good to excellent control from Banner Maxx (2 applications at 4 fl oz), Headway (2 applications at 3 fl oz), and Eagle 20EW (2 applications at 2.4 fl oz) in some studies. Heritage has not provided effective spring dead spot control in our studies.

With any fungicide application for spring dead spot, it is very important that you water the fungicide into the root zone for best results. The pathogen is attacking the roots, rhizomes, and stolons of the bermudagrass plant, so that is where the fungicide needs to be. Most fungicides are absorbed quickly by the foliage, so irrigation must be applied right away before the spray dries on the leaves. On putting greens and fairways, typically 1/8" of irrigation is sufficient, but up to 1/4" may be needed on higher cut areas.

Civitas shows promise for control of dollar spot and brown patch

Since the new fungicide Civitas was unveiled at the GIS Show in New Orleans, we've had a number of questions from golf course superintendents and product distributors about its effectiveness against turfgrass diseases. This year, we evaluated a mixture of Civitas + Civitas Harmonizer for control of brown patch and dollar spot on creeping bentgrass putting greens. So far, the results are promising.

The mixture of Civitas + Harmonizer was applied every 14 days beginning prior to the onset of disease symptoms. Industry standard fungicide treatments were included in each study: Heritage 50WG (0.2 oz every 14 days) in the brown patch study and Banner Maxx + Daconil Ultrex (2 fl oz + 3 oz every 14 days) in the dollar spot trial. The incidence of each disease was assessed periodically during periods of activity.

Civitas + Harmonizer provided good suppression of both diseases. Brown patch incidence was maintained at or below 5% of the turf surface area throughout the study, even under intense disease pressure in late July. Dollar spot incidence was significantly reduced throughout the season, reaching a maximum of 36 spots per plot in plots treated with Civitas + Harmonizer as compared to 160 spots in untreated plots.

The bottom line - Civitas showed good activity against brown patch and dollar spot in North Carolina in 2009. While it did not always provide acceptable levels of control alone, it should prove to be a useful tool for disease management as part of an integrated program.

A few words about the active ingredient in Civitas, which is a type of mineral oil, also commonly referred to as 'horticultural oil'. Horticultural oils have been used for disease and insect control in a number of crops for many years. These products have direct fungicidal and insecticidal activity, and are highly desirable in organic farming due to their safety and short residual in the environment.

Suncor, formerly known as Petro Canada, also claims that Civitas works by inducing systemic resistance in the plant. However, the research supporting this claim has not yet been published.

Anthrancose and summer patch are appearing in the southeast

In yesterday's post Dr. Kaminski asked, "Where is the summer heat?" Well, if you want heat we've got it here in the southeast. Brown patch has been raging for the last month, symptoms of fairy ring have been appearing sporadically, and we are just starting to see anthracnose and summer patch popping up.


A few samples of anthracnose on creeping bentgrass have been submitted to our Turf Diagnostics Lab at NC State, and we also have some developing on 'Dominant Plus' creeping bent at our research center. Conditions have fluctuated between hot and wet then hot and dry, which is ideal for anthracnose development. If you are growing a bentgrass cultivar that is susceptible to anthracnose, be sure that you have a solid preventive fungicide program in place as soon as possible.

Not all bentgrass varieties are susceptible to anthracnose. The Penn A and G series cultivars have good resistance to the disease, and problems are rarely seen on these grasses. Older varieties, like Penncross, Pennlinks, Dominant, and even Crenshaw and L-93, are most susceptible.

Beware that fungicide resistance is a common problem in anthracnose populations. Our recent survey of C. cereale populations in NC showed that resistance to the QoI class (Heritage, Insignia, Compass, Disarm) and thiophanate-methyl (3336 and equivalents) is widespread. In fact, we had a hard time finding populations that are sensitive! Bottom line - unless you know that your populations are sensitive to these fungicides, do not rely on them for anthracnose control. For other anthracnose control options, please see our Anthracnose Information Sheet on TurfFiles. Remember to avoid the DMI fungicides if temperatures above 90F are in the forecast.

If you would like to find out if your anthracnose population is resistant or sensitive to various fungicides, the NC State Turf Diagnostics Lab offers fungicide resistance screening. Please see our website for more details.



Right on time, symptoms of summer patch have started to appear in North Carolina as well. It seems like this disease always starts to appear right around the 4th of July. If you are managing Kentucky bluegrass or annual bluegrass, or have bentgrass greens with a history of summer patch problems, be sure to continue your preventive applications for this disease. The summer patch pathogen is active throughout the summer, as long as average daily soil temperatures are below 80-85F.

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.

Should I water that in?

This is easily the most frequent question I get from golf course superintendents during the growing season. It is a difficult question, and there isn't always an easy answer.

We know that watering fungicides into the root zone is important for effective control of root diseases. However, in the real world, golf course superintendents apply fungicides to control a combination of root and foliar diseases, but we don't always know what effect watering-in has on foliar disease control.

To answer this watering-in question, you need to identify the primary disease you're trying to control, know where this pathogen attacks the turf plant, and understand how the selected fungicide moves in the plant after application.

In most cases, if a root disease is the primary target for a fungicide application, then it should be watered-in immediately after application. Once the spray dries on the leaves, it will be locked into the foliage and will not get into the root zone. Exceptions to this rule are the true systemic fungicides, like fosetyl-Al and the phosphite salts. These products are translocated downward in the plant and do not need to be watered-in.

The Fungicide Selection Tool, a new feature on our TurfFiles website, can help you select the best application technique for your fungicide applications. After selecting your turf species and the diseases you are trying to control, a list of fungicides is displayed. The list is ordered based on average efficacy against the selected diseases. After selecting a product or products to apply, you are taken to a page that displays mode of action, efficacy rankings, risks for fungicide resistance, rates and application intervals, and application instructions for each selected disease.

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.