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Tag: large patch

Large Patch Evaluation Study Update

By: Manoj Chhetri

With temperatures cooling down and days being shorter, we are already starting to see warm-season grasses, including zoysiagrass, going to sleep. At the Rocky Ford Turfgrass Research Center, located in Manhattan, KS, we have shut down the irrigation in warm-season plots.

Our zoysiagrass in the large-patch tolerant breeding plot is not cooperating with us as much as we wanted. We inoculated the field in mid-September with fresh Rhizoctonia pathogen and kept the field pretty wet to encourage fungi to flourish. However, to our dismay, we did not see much of the disease activity, except in a few poor drainage spots. With disease research, it is the type of research where we want disease pathogens to have no mercy on us. We are impatiently waiting for spring, which in fact is a more favorable time of the year for large patch activity.

We are hopeful that we have at least one or two new zoysiagrass progeny that possess greater large patch tolerance. Again, it is hard to make comparison and evaluate when we don’t have disease pressure. So far, we have narrowed down to 10 best progeny out of 60. On the positive note, we have seen more disease pressure on our non-selected progeny than in our top-ten selected progeny. This tells us that we did a good job on choosing those ten-best progeny.

This project is aiming to develop a large patch tolerant zoysiagrass that can significantly reduce cost on fungicides and protect the environment. It is a collaborative project between Texas A & M and K-State University.

Pictured Above: Zoysiagrass progeny evaluated in large patch disease environment.

Pictured Above: One of the zoysiagrass progeny showing large patch in one inoculated half (right side) and fungicide treated cleaner side on other half (left side).

Temperature fluctuations and turf diseases

(Megan Kennelly, KSU Plant Pathology)

As I write this on Thursday we are looking into a weekend with forecast lows deep down into the 30’s. This comes after a September with multiple days in the 90’s and even more in the upper 80’s. Depending on how the weather shakes out after this weekend our warm-season turf may start showing signs of dormancy. Right now it is all still quite green.

In our cool season turf I’ve not seen much dollar spot lately, and it should be simmering down. I have heard a few reports of rust,

and my first suggestion in those cases is to review the fertility regime and make sure it’s not too low on N.

We are seeing and hearing reports of large patch across the region. Here is one example from today at our research facility in Manhattan:

Spring dead spot happens in … spring. But fall is a time to think about it. I’ll point you to an excellent summary of fall disease info from Dr. Miller next door in Missouri, with details about large patch, spring dead spot and other diseases:



Zoysia breeding line evaluation work continues

(Megan Kennelly, KSU Plant Pathology)

KSU continues its work with the turf breeding team at Texas A&M and colleagues at Purdue. We recently inoculated some breeding lines with the large patch pathogen. We grow the fungus on sterilized oats then bury it just under the thatch layer. Sometimes we see symptoms in fall, but often we do not see them until spring. Scientific research takes a lot of patience :). In the meantime, we are keeping the plots moist to foster fungal growth.

In the meantime, large patch is active especially in wet areas:

Take note of these areas. It’s too late to fertilize zoysia now, but when spring comes around a bump of slow-release N may prompt recovery. In the meantime there may be actions you can take to improve drainage.

Spring fertilizer won’t make large patch worse

Can I fertilize my zoysiagrass now? I’m seeing large patch.



Large patch is caused by Rhizoctonia solani AG 2-2LP. Brown patch of cool season turf is caused by closely related strains of R. solani. We know that fertilizer during brown patch season will enhance disease.

So – does spring fertilization increase the severity of large patch?

KSU collaborated with Dr. Lee Miller at University of Missouri to answer this exact question. The paper was just published in Crop, Forage, & Turfgrass Management and the abstract appears HERE. One of the authors, Ross Braun, worked on this project as part of his M.S. project.

At both sites, we applied fertilizer (calcium nitrate, ammonium sulfate, or urea) when the 5-day 2-inch soil temperatures reached 60 or 70ᵒF in spring or fell to 70ᵒF in fall. On those dates, the turf received 0.75 lb N/1,000 sq feet. Those treatments also received some summer nitrogen, too, with 0.25 lb N/1,000 in each of June, July, and August. So, all treatments received a total of 1.5 pounds N/1,000 sq feet/year. These early spring, late spring, and fall treatments were compared to summer-only controls which also received a total of 1.5 lb N/1,000 sq ft applied as 0.5 pounds in each of June, July, and August. We measured percent green cover using digital image analysis. Both studies were done in the cultivar ‘Meyer’ at fairway height.

Image of plot, and digital image with green pixels captured:

example example-reverse

The grand summary is that the spring fertilizer applications at either 60 or 70ᵒF did not lead to higher large patch severity compared to the standard summer-only treatment. This builds on and confirms prior KSU work by PhD student Ken Obasa  (click HERE for the abstract of the publication) where we also found that spring applications did not enhance disease, though in that study we did not use defined soil temperature thresholds. In that study we found that spring and fall fertility sometimes had greater green color than summer fertility treatments.

Right now in Manhattan, our 2-inch average soil temps are in the low to mid-60’s, so we are in the range where those spring fertilizer applications were shown to be “safe.” We did not look at fertility at temperatures lower than that. So, you should be in the clear, and a little N may boost green color and help you grow out of the disease symtoms.

What about nitrogen source? On some of the rating dates at both sites, disease severity was higher in plots treated with ammonium sulfate compared to other sources. The effect was not huge, but was significant, so you might want to shy away from ammonium sulfate if you have some large patch at your site.

Dr. Miller’s program is following up with even more studies to hone in on large patch and cultural practices, so we will stay tuned to see how those turn out.

A rainy spring meets a rainy summer. A cornucopia of turfgrass diseases

(Megan Kennelly, KSU Plant Pathology)

We are at the junction/transition of spring to summer. Large patch is still raging in the zoysiagrass. Dollar spot is active in bentgrass and other susceptible turfgrasses, especially in susceptible varieties. In addition, we’ve had some nights with lows in the upper 60’s or low 70’s, and that can mean brown patch activity. It’s a busy time for diseases. As one of my colleagues said, “It’s a fungusy sort of year here in Kansas.”

With all the rain, it’s been hard to keep up with the mowing. We are feeling it at Rocky Ford, with Cliff and the students busy mowing whenever they can sneak it in. And, it’s hard to spray fungicides when it rains every other day. I put out a trial this past Monday since it was the only day that looked clear. Good thing it was not on the agenda for yesterday, when we had 3 thunderstorms in the same day!

Large patch is still rolling in the zoysia:


Dollar spot is active:

dollar spot

Brown patch might not be far behind:


With all the wet, saturated soils there could by Pythium root rot as well:

Copy of pythium-bentrass-2006

(Pythium spores stained pink in the microscope).

As a final note, I’ve gotten some questions and photos recently about algae.

IMG_2617 IMG_2618

Like other weeds, algae likes to take advantage of thinned out turf. Saturated soils and poor root growth can thin out the turf, and algae loves wet conditions. If you didn’t know where your drainage problems were, algal growth can point the way. There are some fungicides labeled for algae, but addressing the underlying site issues is key.

For a list of fungicides for algae, check HERE and go to page 7.


Large patch activity

(Megan Kennelly, KSU Plant Pathology)

With all the recent rain, large patch in zoysiagrass is definitely active. I’ve already posted some info, here are just some more photos to show symptoms at Rocky Ford. The top two are at fairway height, and the bottom shows the disease at two mowing heights.

010 012 015

2015 Fungicide Resource

(Megan Kennelly, KSU Plant Pathology)

Hello everyone,

The 2015 edition of Chemical Control of Turfgrass Diseases is available at the following website:




This guide from University of Kentucky (Paul Vincelli and Gregg Munshaw) is updated every year with new products and all the latest research findings. Bookmark it, print it, use it, love it.



Some early large patch, and nutsedge too

(Megan Kennelly, KSU Plant Pathology)

Thanks to Mark Newton at Deer Creek Golf Club in Overland Park for sending in these photos. Mark said it was alright to share where these came from – thanks Mark! We always appreciate reports and photos from the field. If you are okay with us putting your name on there, that’s great, and if you prefer to stay anonymous, that works too.

Anyway, Mark is seeing some early large patch in the zoysiagrass fairways. This past week has been hot, but we’ve had some cool spells that could have given the fungus a kickstart. And, we’ve had some rains, too. Large patch is favored by wet conditions. Symptoms are most common and tend to be most severe in spring, like April through early June. In the fall, we sometimes see symptoms in September, but it can occur earlier or later.

In fungicide trials at KSU we’ve seen good results suppressing symptoms the following spring by applying fungicides once in September. We’ve applied as early as Sept 3 and as late as Sept 30th and gotten good results with all those timings, using DMI’s, QoI’s, and flutolanil. The temperature in the thatch has been 65-70 degrees during those application timings.

Along with the large patch, there is some nutsedge action and a good pic of that is shown below as well.