Civitas, Nematodes, and Heat in the Southern Plains

As I mentioned the last time I posted, I promised to summarize some information that was presented at our Turfgrass Pest Management Field day held on June 15^th in subsequent posts. So here goes…

One of the fungicide trials that we toured during field day included several different fungicide formulations for control of dollar spot and brown patch on creeping bentgrass putting greens. In this particular trial we applied the newer fungicide Civitas + Harmonizer alongside other conventional fungicide products. As you may remember in previous posts here and here by Dr. Tredway, Civitas performed well for control of dollar spot and did not cause phytotoxicity in North Carolina trials.

In our trial this spring we observed poor control of dollar spot by Civitas + Harmonizer as a “curative” treatment. When this study was initiated we had a raging dollar spot epidemic well under way on April 18. After three applications of fungicide on a 14-day interval, most treatments still had substantial dollar spot present and poor overall turfgrass quality compared to the rotation of 3336 plus and Emerald. This included the Civitas + Harmonizer treatment which had comparable dollar spot severity and quality to the non-treated control.

Why didn’t Civatas work as well in our study as it had in other studies? Our hypothesis is that it is because the product was used as a “curative” in this case. Civitas works by induced systemic resistance (ISR), another words the product “turns on” defense responses in the turf plant. This means that the product must be taken up by the plant and elicit the appropriate responses in the plant before the plant can fight the infection by the dollar spot fungus. This process can take time in the plant. Therefore, the best results will likely be observed when Civitas is applied preventatively and the plant is provided sufficient time for the appropriate responses to be “turned on” and brought “up to speed.” In our study, Civitas was applied after the infection and the plants resistance mechanisms were not incited, which is likely why we observed very poor control of dollar spot by this product. Most of the other products applied in this “curative” fashion also provided relatively poor results with the exception of the 3336/Emerald rotation. These results further substantiate the importance of using preventative fungicide applications versus curative applications when at all possible.

In other news out of the southern plains…can you say HOT! It has been consistently in the triple digits now for several weeks in Oklahoma. June 2011 will likely go down as one of the hottest on record. In the OSU Turfgrass Diagnostic Lab we have been getting many creeping bentgrass samples with heat stress. We have also seen some Pythium blight on greens being over-irrigated to compensate for the hot temperatures. Anthracnose has also been diagnosed on several greens from the eastern part of Oklahoma.

In addition to cool-season turf samples coming in due to heat stress, we received several more creeping bentgrass samples with very high levels of plant parasitic nematodes (mostly stunt and ring nematodes). As I mentioned in my previous post, levels this high in June, will result in extremely high populations of nematodes later on in the summer when plants will already have the added stress of summer heat. Several of the courses with these problems are reporting that areas of the putting greens are beginning to fade and the decline is slowly spreading. With the continued 100 F + heat we have been experiencing in the south-central U.S. and the golfer traffic likely over the Independence day holiday, the stress that the nematodes are imparting on these greens will be further magnified. We are encouraging good cultural management including raising mowing heights (.160 in. or more would be advised), adjustment of the frequency of mowing and rolling to reduce the amount of stress applied to the turf stand, and continued frequent, light applications of fertilizer and water. Any practice that reduces stress and damage to turf plants will help plants plants in surviving the additional damage that nematode feeding causes. Hopefully we can get a break from the heat soon and reduce some of the stress on creeping bentgrass putting greens in our neck of the woods.

A Blog and Disease Update

So far the summer has been very busy for all of us and I personally apologize for not posting as much as I would like. You would think that posting an update a week would be easy, but it is once again proving difficult with all of the research, internship visits, website development and other things that I am currently working on. The good news is that we are rolling out several new bloggers to the site in the next month. I will let them introduce themselves in their first post as Dr. Damon Smith did in his first post from Oklahoma. We are also working on a redesign and launch of a more substantial website (not sure of a roll out date, but at this rate it will be in 2012) which will provide even more information about turfgrass diseases and likely some other areas of focus. So look for that in the future and in the meantime please welcome our new bloggers as they start to post!

In terms of diseases around the region, there is still a lot of talk about the etiolation of bentgrass on putting greens in the mid-Atlantic (and other areas as well). While there have been reports of a bacteria found in association of these symptoms there are as many reports of the symptoms being present without any bacteria found. The bottom line is that the verdict is still out regarding the cause of these symptoms and the impact that this will have as we move closer to the middle of the summer. While I am still skeptical about topic as a whole, I concur that if you are experiencing these symptoms you should perform basic cultural practices to minimize stress as if you had bacterial wilt. These include:

• Raising mowing heights
• Utilization of a dedicated mower for the affected greens
• Mowing when the greens are dry
• Maintaining greens as dry as possible
• Avoiding abrasive cultural practices (e.g., topdressing, vertical mowing, etc)
• While there are no real control measures for BW, the use of Copper-based fungicides may help a little.

Additional diseases that are appearing at this time include your typical brown patch and dollar spot, an unusual basidiomycete associated with what has been called "thatch collapse" (image right), anthracnose, fairy ring, root pythium and probably others that I am forgetting. In general, this is the time when most of our summer diseases start kicking it into high gear.

For more information on Bacteria , you can visit a search I did on this blog.

A New Blogger and Updates from Oklahoma

Yes, the title is correct, I am new to the Turf Diseases blog. The bloggers who you have been reading over the last couple of years have invited me to contribute to this effort. I sure appreciate the invitation and hope that I can present some useful information to increase your success in managing turfgrass diseases.

Before I get into some updates from my area, I wanted to just take some space to introduce myself. I am a native of western New York State (I grew up in the Finger Lakes region). I received my B.S. in Biology from the State University of New York, College at Geneseo (SUNY Geneseo). I then moved to North Carolina and completed my M.S. and Ph.D. degrees in plant pathology from North Carolina State University. I am currently an assistant professor of turfgrass and horticultural crop pathology in the Department of Entomology and Plant Pathology at Oklahoma State University. I have been on the faculty at OSU for 4 years now. I specialize in epidemiology (study of plant disease epidemics and how to control them) and disease forecasting systems for plant diseases. I have developed and/or tweaked several disease advisory systems for various crops including turfgrass (more on that in a future post.) While I am not exclusively a turfgrass pathologist, I spend about 75% of my time diagnosing, studying, and delivering information about turfgrass diseases. I also have responsibilities for other crops such as ornamentals, grapes, pecans, and stone fruits. Some of you might think that all of these responsibilities might hinder my ability to be an expert in the turfgrass pathology field, I would argue otherwise. I believe that my experiences in diagnosing and managing disease of other crops give me a unique perspective when it comes to studying turf diseases and developing recommendations to manage them. I hope that my broad background and knowledge of disease management in many cropping systems will translate to useful information for you in these blogs.

Well, enough about me. I’m sure all of you are curious as to what has been happening in Oklahoma. Last week we hosted our first ever Turfgrass Pest Management Field Day. We concentrated mostly on turf disease and weed research, but also heard about Zoysiagrass mite from Dr. Nathan Walker, Turfgrass IPM Specialist. Dr. Walker also spoke about spring dead spot research at OSU and also new research on nematode management in bentgrass putting greens. Dr. Dennis Martin, turfgrass specialist, spoke about creeping bentgrass evaluations for dollar spot resistance. Dr. Justin Moss, turfgrass water management and environmental impact specialist, spoke about annual bluegrass control on creeping bentgrass greens using some new experimental herbicides. I finished things off with research updates on dollar spot in creeping bentgrass putting greens, brown patch in tall fescue, and large patch of Zoysiagrass. We had about 50 in attendance despite the near 100 F temperatures. We would like to thank all who attended and look forward to another successful Turf Pest Management Field Day in the Future. I will summarize some of the research presented at the field day in some subsequent posts.

The OSU Turfgrass Diagnostic Laboratory has been busy over the last couple of weeks. We have been receiving quite a few creeping bentgrass samples. This is not surprising considering that we have topped out between 90 F and 100 F every day for the past 20 days! Over the last month we have seen some stressed bentgrass succumbing to the heat and also some typical diseases such as Pythium blight, fairy ring, spring dead spot on bermudagrass, and nematodes on creeping bentgrass putting greens coming into the lab. The latter is most troublesome as we had a tough time last season with nematodes on putting greens in Oklahoma combined with the heat. All of this heat early on, not only is going to stress the bentgrass plants, but will also encourage rapid increases in nematode populations, which further stress creeping bentgrass. In a recent submission that arrived in the turf diagnostic lab from within the state of Oklahoma, a nematode extraction was performed (sugar flotation method using 100 cc of soil) and the following nematode populations were identified in two different putting greens (their corresponding action thresholds are also indicated).

Green #1
Sting nematode - 76/100 cc soil; action threshold = 20/100 cc soil
Sheath nematode - 57/100 cc soil; action threshold = 200/100 cc soil
Ring nematode - 235/100 cc soil; action threshold = 500/100 cc soil
Stunt nematode - 396/100 cc soil; action threshold = 150/100 cc soil

Green # 2
Sting nematode - 11/100 cc soil; action threshold = 20/100 cc soil
Sheath nematode - 0/100 cc soil; action threshold = 200/100 cc soil
Ring nematode - 344/100 cc soil; action threshold = 500/100 cc soil
Stunt nematode - 794/100 cc soil; action threshold = 150/100 cc soil

The sting and stunt nematode populations are very worrisome this early in the season. As the season progresses, nematode populations will continue to increase resulting in further damage to roots. The combined effects of all of these various nematode species are also troublesome. Having several different populations causing various forms of damage to the roots of these plants will certainly have a negative effect on the condition of the greens later in the season.

No chemical control recommendations are currently available to the golf industry in Oklahoma (no certified Curfew applicators in Oklahoma), unless the manager has access to residual supplies of Nemacur. If a superintendent can get their hands on Nemacur, care should be taken applying this product and reapplication will likely be necessary to be effective at reducing the population of nematodes present. Cultural management should include raising mowing heights (.160 in. or more would be advised), adjustment of the frequency of mowing and rolling to reduce the amount of stress applied to the turf stand, and continued frequent, light applications of fertilizer and water are recommended. Any practice that reduces stress and damage to turf plants will encourage root growth and assist the plants in surviving the additional damage that nematode feeding causes. Superintendents are also encouraged to continue with a preventative fungicide program to manage fungal pathogens that can cause further damage and stress to the plants.

That's all I have for now! Until next time...

dollar spot, brown patch, a bit of heat, and what do you do when you don't have a sprayer?

Hello,

I am back in the US after an agriculture development trip to Tajikistan. If any of you are curious about that, you can check out this website where I have some notes and photos. The photo above is me with the Tajikistan-Afghanistan border mountains in the background.
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https://picasaweb.google.com/mmkennelly/TajikistanVisit2011?authkey=Gv1sRgCMvxxJn_moCCKg

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Anyway, back here on the home front dollar spot is active in putting greens and fairways. Though I have not seen it yet with my own eyes, I have had a few reports of brown patch activity as well.

In addition, with some of the recent heat and wind there are some hot spots cropping up. Even though the irrigation is on, the hot dry winds may be reducing the water that actually gets down onto the surface in all spots. When it comes to hand-watering, make sure to put an experienced crew member on the task, since it can be kind of an art.

I keep thinking back to 2010... you want to minimize turf stress now before the really nasty summertime comes along.

In addition to hot spots, localized dry spot may be appearing in some places. The droplet test is always a good indicator:




No sprayer?

I had an interesting question today from a low-budget course that is having dollar spot issues. The course is in a small town in Kansas, and the place is so low-budget that they don't have a sprayer. They are relying on granulars.

Of course, one issue with that is that they aren't going to get the same coverage as with a spray. Then, it limits the chemistries that they can use. Not many materials are available in granulars.

It sounds like they have used a lot of thiophanate-methyl. Unfortunately, in some recent work in Kansas, I observed that most isolates are resistant to that mode of action.

The course has also used a lot of a granular triadimefon. As we all know, the DMI's can have resistance problems as well. The other granular they have used is iprodione.

So, there could be some resistance issues, and there are definitely some application-method challenges that may not be fixable.

It is an interesting situation, and I'll welcome any suggestions by you folks out there in the blog-o-sphere.

Mites, Weather, Australia, and Dollar Spot

I'm posting this from Australia where the winter is just beginning. At the Redlands Research Station near Brisbane today I saw plenty of dollar spot on seashore paspalum. Pictured is a plot of Sea Isle Supreme. These are the typical symptoms of dollar spot that occur when the growth of seashore paspalum is slow.

I also saw some interesting mite damage yesterday on bermudagrass (or green couch as it is called here). From a distance the area pictured below looked as if it were suffering from drought stress, but upon closer inspection these severely stunted shoots, so typical of mite damage, were found. Last year I saw mite damage at Bangladesh and wrote about it in this post.

At Thailand last week I visited four golf courses. There were two with zoysia greens and two with TifEagle greens. One had seashore paspalum fairways, one had zoysia fairways, another had bermudagrass fairways, and another had native grass fairways. I'm fascinated by the types of warm-season grasses that grow in different parts of the world, and clearly the weather has a lot to do with that. Some grasses thrive in one area, while others struggle. I put together a series of bubble charts that plot world cities by their climatological normals, the average weather data over a number of years.

I'll be updating these charts monthly on www.blog.asianturfgrass.com. As the northern hemisphere summer progresses, we will see that transition zone cities such as Atlanta, Osaka, Shanghai, and Tokyo move very close on this bubble chart to places where only warm-season grasses are grown such as Miami, Singapore, and Tahiti. The difficulty of managing cool-season grass during the summer is shown clearly when the average weather conditions are the same as in tropical cities.

Zebra patch

Hi,

I don't have a lot of news, but I wanted to share these very cool photos that were sent by Darin Pearson at Eagle Bend Golf Course in Lawrence. The course is stripping zoysia into rye, and you can see how the large patch is expressed in the susceptible turf (zoysia) while leaving the rye seemingly untouched.

Starting tomorrow I'm off to Tajikistan for about 10 days.

I wonder how the turf world will change while I'm gone. It could be cool and rainy, hot and dry, hot and sticky... we'll see. It's always interesting to see how quickly diseases can come and go in our variable climate. So far, there hasn't been any dollar spot here in our research plots, for example, but it could take off soon... or not, depending on what Mother Nature does.

Beautiful Weather, Finally?

This spring has been one of the coolest and cloudiest on record. Just last week I was in Stevens Point, WI and soil temperatures barely reached 60 F. Still prime time for take-all patch and fairy ring preventative applications. To be honest not much is happening around the Upper Midwest. We have had reports of brown ring patch, but thats about it. Derek Settle at the CDGA has reported brown ring patch and a bit of dollar spot. We have seen and heard of multiple cases of creeping bentgrass turning red this spring. We think it is a combination of proxy/primo or trimmit + DMI fungicides for take-all/fairy ring + cool temperatures. The symptoms are typically seen on older leaves and we cannot find spores of any kind in the samples. An image of the symptoms we are seeing is above, sorry the image does not show the symptoms very well. If anyone has any thoughts on this matter they would be welcomed and appreciated!

Finally I thought I would reiterate a former post Lane wrote. He presented a succinct description of diseases that typically affect creeping bentgrass and annual bluegrass putting greens. There has been concern in the Midwest with the substantial amounts of rainfall we have received that Pythium root rot could be a problem. Yes Pythium root rot could occur at anytime as long as the soils are saturated, but considering creeping bentgrass and annual bluegrass grow well during the spring I rarely think of Pythium root rot as an issue. This brings me to another point Lane made in a previous post, is Pythium root rot a disease. I think it is a disease because we would not see symptoms characteristic of root rot if the pathogens were not present. Keep in mind though once/if summer rolls in and we continue to receive significant rainfall, then we might see issues with this disease. I am not saying that fungicides are not warranted, but I do think it is unlikely that Pythium root rot would/did occur this spring in the Midwest.