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We have moved our website from turfpathology.org to turfpathology.plantpath.ncsu.edu. Please make note of this change.

We will start posting alerts and disease updates on this new site instead of using this blogger site. These posts will still feed to Facebook, Twitter, and LinkedIn if you follow us there.

We hope you all have a fantastic year growing disease free turf!

Return of the Fungi!

Things have been relatively quiet here at the NC State Turf Diagnostics Lab with regards to disease samples, however that has changed in the past couple of weeks now that warm-season turfgrasses are starting to fully wake up from their winter nap. So, without boring you to death with blah blah this and blah blah that ... here's the rundown.

Warm-Season Turf (Bermuda/Zoysia/Centipede)

Many samples have been submitted both digitally and physically to the clinic over the past few weeks that have shown winter damage. The majority of these samples were taken from shady, wet, and/or north facing slopes. These are typical areas we expect to see this type of damage on warm-season turfgrasses. In most cases, it appears that green up has been delayed and no complete turf losses have been reported. The exception to that has been centipedegrass. We have seen some centipede lawns that we can't find any disease, insect, nematode, soil problem, etc. where winter kill is strongly suspected. This is all unfolding as I type this, so we may see cases of other warm season turfs with winter kill as they continue to fully green up across the state. For more information about winter injury in North Carolina, please read Dr. Grady Miller's recent post by clicking here.

From a disease standpoint, the most common diagnosis in the past week or so has been spring dead spot on bermudagrass. This has been documented on common, hybrid, and ultradwarf types. Given the fact that spring dead spot is highly correlated with cold injury, it is no surprise that there is a lot of spring dead spot damage out there this year in North Carolina. There is nothing you can do from a fungicide standpoint at this time to recover from this disease because the damage was done last fall. For more information about spring dead spot, please click here.

Spring dead spot symptoms on ultradwarf bermudagrass

Spring dead spot symptoms on hybrid bermudagrass

Typical winter kill symptoms on warm season turf

Cool-Season Turf (Bentgrass & Ryegrass)

As expected, we haven't seen many cool-season turf samples in the past few weeks since they are able to withstand the ravages of fungi for the most part in the spring and fall.

One exception has been red leaf spot, caused by the fungus Drechslera erythrospila, on creeping bentgrass putting greens. This is a disease we have observed over the past several years. For the most part, it has been fairly random and isolated, however we are starting to see more and more of this disease for whatever reason. If you think you have red leaf spot, now is the time to treat. None of the samples that have come into the clinic are producing spores yet. This tells us that while the fungus is waking up and starting to infect via mycelium spread, it hasn't reached it's full potential to produce abundant spores. Once spores are produced, the damage will be more widespread and rapid. For more information about red leaf spot, click here.

Red leaf spot symptoms on a creeping bentgrass putting green

Finally, we have observed some dollar spot damage on perennial ryegrass in over seeded situations. Recent weather patterns have been favorable for this fungus to start coming out and eating away at our precious stands of perfect turf, so beware! If you haven't started your preventative dollar spot programs, now's the time ... especially on high value turf like creeping bentgrass. For more information about dollar spot, click here.

Dollar spot symptoms on perennial ryegrass

Cream Leaf What?

Cream leaf what? That's the exact response I've heard from superintendents over the past several weeks when I tell them their ultradwarf bermuda putting greens have a disease known as cream leaf blight. To answer your first question, cream leaf blight is not a new pathogen to turfgrass. It has been documented on creeping bentgrass and tall fescue. As more ultradwarf bermudagrass replaces creeping bentgrass for putting surfaces here in North Carolina, we will likely observe more new diseases. This disease has been diagnosed on both 'Champion' and 'Mini Verde' and we are in the process of complete confirmation of the causal fungus via DNA analysis.

 

Typical white patch symptom observed on ultradwarfs
in December/January in North Carolina

Cream leaf blight is caused by the same pathogen that causes pink patch, Limonomyces roseipellis. Pink patch is often found in close association with red thread, which is caused by the fungus Laetisaria fuciformis. Pink patch and cream leaf blight vary slightly in their morphological features, which we are able to detect under the microscope. For those of you who are plant pathology geeks, pink patch produces clamp connections and cream leaf blight does not. Otherwise, from what we've observed, the two appear identical in the field and we will most likely refer to it as cream leaf blight since that seems to match the stand symptoms the best. One unique characteristic is the mycelium will twist into "rope" like structures, as seen below.

Mycelium twisting into "ropes" for both cream leaf blight and pink patch (25x)

Close up of cream leaf blight hyphae twisting into a "rope" (200x)

While we don't know much about cream leaf blight on bermudagrass yet, we have only observed cosmetic damage and nothing that leads to turf loss or significant reduction in playability. We have been recommending fungicide applications of products like 26GT, ProStar, Heritage, Insignia, or Disarm since they have been proven performers with pink patch/red thread complexes.

If you are observing this type of symptom at your course and have questions, feel free to contact us!

Bermudagrass Greens Looking Bad?

Recent weather patterns of cool/cloudy/rainy weather across much of North Carolina have been perfect for foliar diseases such as Bipolaris leaf spot and Pythium blight on bermudagrass putting greens.

Bipolaris Leaf Spot Symptoms on Ultradwarf Bermudagrass

We have received many samples in the past week at the NC State Turf Diagnostics Lab that were devastated by the fungus Bipolaris cynodontis. Bipolaris leaf spot is most severe on turf that is growing slowly due to adverse weather conditions or improper management practices.  Shaded areas with little or no air movement result in weak turf and extended periods of leaf wetness that favor disease development. Deficient or excessive nitrogen, excessive thatch, extended periods of leaf wetness, and low mowing heights are factors that encourage the development of leaf spot diseases. The fungus is easily spread by mowers, wind, and/or rain.

For more information about Bipolaris leaf spot, including control recommendations, click here.

Ultradwarf Bermudagrass Devastated by Pythium Blight
(note mycelium on leading edge)

We have also diagnosed many bermudagrass samples this week with Pythium blight in conjunction with leaf spot or acting alone. The symptoms are a rapid foliar blight that initially has a purple coloration but then fades to tan. Spreading by mowers or in drainage patterns usually occurs as well. 

Pythium blight in October? Yes, you read it correctly, it is Pythium blight in October. There are a lot of Pythium species that can infect grasses. Most people are familiar with P. aphanidermatum that causes Pythium blight on the cool season grasses during hot summer weather. However, there are other Pythium species that grow during cool or cold weather. We don't know what species is causing this outbreak yet, but obviously it grows well during cool weather and has a competitive advantage over the bermudagrass under these conditions.

Fungicide treatments may not always be necessary to control Pythium blight on bermudagrass, as dry and sunny weather usually put a stop to it very quickly. However, if the forecast is calling for extended periods of wet and cloudy weather, an application might be a good idea. Any strong Pythium fungicide should do a good job.

What's Happening Now?

RECENT CREEPING BENTGRASS PROBLEMS

Over the past several weeks, we have received many creeping bentgrass putting green samples.  In every case, samples were submitted to check for a disease and in EACH case absolutely no pathogen activity was discovered.  Therefore, our diagnosis was "a disease was not responsible for the damage".  The common thread has been the combination of core aerification and topdressing with the unusually arid weather for this time of year. When the putting surfaces are opened up after aerification, they are more susceptible to drought stress, especially if the humidity is very low. This effect is exacerbated in areas that are already stressed such as clean up laps, heavy on/off traffic spots, etc.

This is a fine example of why receiving a diagnosis of "no disease" is just as important as receiving a diagnosis of an actual disease. Because symptoms developed during excellent growing conditions for creeping bentgrass, a safe assumption is a disease is responsible for the damage.  Yet, in this case an accurate diagnosis can save time and money by preventing unwarranted fungicide applications.  If you don't agree, feel free to make a fungicide application for drought stress and see what happens.

Typical Stress Symptoms Observed with Recent Samples

TREAT FOR LARGE PATCH NOW!

With soil temperatures starting to approach 70°F across portions of NC, now is the time to treat for large patch.

Average Daily Soil Temperatures as of 10/01/13 via NC State Climate Office

Large patch, which is caused by the fungus Rhizoctonia solani, is a common disease of centipedegrass, St. Augustinegrass, zoysiagrass, and bermudagrass grown for lawns, landscapes, golf turf, and athletic fields. Centipedegrass and St. Augustinegrass are particularly susceptible to severe damage from this disease.

Symptoms of large patch appear in roughly circular patches from 2 feet up to 10 feet or more in diameter. The affected turf will initially be orange, yellow, or reddish-brown in color but will then turn tan and collapse to the ground. The disease can spread rapidly to encompass large areas of turf, and distinct circular patches may not be obvious in these cases.

Fungicides are available for large patch control, but they must be applied preventatively for best results. The first application should be made in the late summer or early fall when average daily soil temperatures are 70°F or below.

One fungicide application will control minor cases of large patch, but two to three applications on a 4 to 6 week interval may be needed to control severe cases. Fungicides are not very effective once the symptoms of large patch appear. Curative applications will help to reduce further spread of the disease, but the affected turf will be very slow to recover.

For more information about Large Patch, including images and specific control recommendations, click here.


TREAT FOR SPRING DEAD SPOT NOW

So, your first question may be "Why on Earth are you telling me to apply fungicides for a spring disease in the fall and for something that will not show up for another 6-7 months?!"  The answer is simple.  The causal fungus, Ophiosphaerella spp., is active RIGHT NOW and you can bet it's infecting your bermuda and zoysia grass plants as I type this blog.  We know through years of research that fungicides are most effective when the soil temperatures are between  60 - 80°F in the fall of the year.

Choosing the right fungicide and applying at the right time will not result in acceptable levels of control if you do not apply them correctly.  Spring dead spot infects below ground plant parts.  With that being said, you must either water-in your fungicide applications IMMEDIATELY  with 1/4" of irrigation or apply with a carrier volume of 5 gal/water/1,000 sq. ft.  You need to be running your irrigation the moment the applicator is out of the way.  Do not wait until the following evening or night with your routine irrigation schedule or else you may be severely disappointed come next spring when these grasses green back up.

Just recently we have made some fantastic discoveries with fertilizers in regards to controlling this disease without having to use fungicides at all!  To learn more about this, please click here.

To learn much more about spring dead spot, including control recommendations, please click here.

Now Accepting Credit Cards!

We have finally joined the rest of the world in the 21st century and can accept Master Card or Visa for services rendered through the NC State Turf Diagnostics Lab.

If you currently have an outstanding invoice with us, you can contact me via email and I will send you the payment link.

If anyone has any questions about this new option, please contact me.

Lee Butler
NC State Turf Diagnostics Lab
(919) 513-3878
lee_butler@ncsu.edu

What Disease?

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

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

Summer patch symptoms on creeping bentgrass

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

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

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

Pythium root rot following drainage route

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