Guess What? Pythium LOVES Water!

If you've learned nothing else about turfgrass diseases, fungi love water and while not technically a fungus, the oomycete Pythium absolutely adores water. Now, you're sitting there thinking "boy, it sure has been wet lately across much of North Carolina, especially in western NC, and instead of reading this blog post, I should be firing up my sprayer and putting out something to prevent Pythium diseases." Well, if that's not the thought you had ... you better switch gears and make it happen.

Rainfall Estimates for Last 30 Days

For those of you managing bermudagrass putting greens or if you're trying to grow in a freshly seeded stand of anything, you better be on the look out for Pythium blight. We have diagnosed Pythium blight on 'Champion', 'Mini Verde', and 'Tifeagle' bermudagrass putting greens over the past couple of weeks. They are not bullet proof folks! We've also seen a lot of yellow patch on the ultradwarfs, but we'll save that for another day.

For those of you managing creeping bentgrass putting greens, you better be starting up your Pythium root rot prevention program. Two of the biggest misconceptions associated with Pythium and creeping bentgrass is that Pythium blight is common on putting green heights and Pythium root rot only occurs during the hot days of summer. Both are false. We rarely see Pythium blight on creeping bentgrass at putting green heights, especially if it's a well established mature stand. We have diagnosed Pythium root rot on creeping bentgrass putting greens in North Carolina in every month except the winter time.

For more information about Pythium blight and root rot, including control recommendations, visit the links below.

Pythium Blight

Pythium Root Rot

Winter Patch Diseases Now Flocking!

Recent weather patterns, as weird as they may be, have been favorable for two common winter time diseases to start showing up across portions of North Carolina. They are Microdochium patch (a.k.a. pink snow mold) and yellow patch (cool weather brown patch).

As most of you know, Microdochium patch doesn't require snow cover and isn't necessarily pink in color, although if you look at the picture below, you can see that the mycelium does indeed have a pinkish tone. Infection areas may start out as small as 2" in diameter and expand up to 12" over time. The leading edge of the patch may have a reddish brown or salmon color and the leaves in the middle will be collapsed and matted upon themselves. Also, this fungus is a heavy spore producer, so the damage may appear as if it has been spread or smeared by mowers, equipment, water, etc.

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

Pinkish Flock of Microdochium Mycelium

Microdochium Patch

Microdochium Patch

Yellow patch is a very common disease of cool season turfgrasses this time of year and typically causes irregular patches up to 3 feet in diameter that are yellow in color. On creeping bentgrass putting greens and other lower cut turfgrasses, it reminds me of sweat rings in an old ball cap.

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

Yellow Patch on Creeping Bentgrass

Yellow Patch on Ryegrass

Do growth regulators and biostimulants cause yellow etiolation of creeping bentgrass?

We've been seeing yellowing and etiolation of creeping bentgrass greens in North Carolina off and on since 2005. Some people are calling this 'bacterial wilt', but there are two problems with this name. First, no one has proven that this condition is caused by a bacteria. Second, and perhaps most obviously, wilt isn't one of the symptoms!

So, can we all agree to call it yellow etiolation instead of just slapping another erroneous name on it? I know that 'etiolation' is difficult to pronounce, but you can hear its correct pronunciation and practice along at thefreedictionary.com/etiolation.

Early on, I had a theory that biostimulants and/or growth regulators were involved in either causing this yellow etiolation or increasing its appearance. I wanted to share a couple of pictures recently sent to me by golf course superintendents that provide even more evidence of their role in this condition.


This first picture was taken at one of our research sites. Our plots were positioned in a ring around the cleanup pass of this green, and we asked them to avoid spraying our plots when they made certain applications to the greens. The area to the right that is declining severely received their sprays containing a biostimulant product and the growth regulator trinexapac-ethyl. As you can see very clearly, the areas NOT receiving these sprays are much more healthy than the areas that were sprayed.



This second picture was sent to me by a golf course superintendent in Pennsylvania. You are looking at a collar-height walkway between a green and a tee. The area to the left of the red dotted line received double applications of Primo, one along with the greens applications and another along with the tee applications. You can clearly see that the yellowing, etiolation, and thinning of the bentgrass is much more pronounced in the area receiving higher rates of Primo.

So what is going on here? To me, this is looking more and more like a physiological condition rather than a disease problem. We are still unable to consistently isolate any single pathogen, bacteria or otherwise, from turf exhibiting these symptoms. We are planning research to look at the influence of growth regulators and biostimulants on this problem. Until then, I suggest that superintendents who are battling this problem eliminate biostumulants from their programs and also avoid use of trinexapac-ethyl during periods of summer stress.

Watch out for yellow patch on putting greens and landscapes

Yellow patch on an annual bluegrass putting green

Given the cool, wet weather we've had over the last few weeks, golf course superintendents should be on the lookout for yellow patch in their creeping bentgrass putting greens. This disease is also known as 'cool-season brown patch', but the symptoms are very different. Yellow patch appears in irregular rings and arcs that are yellow, or sometimes white. Some people say it looks just like sweat rings on an old baseball cap.

Yellow patch can also occur in landscapes established with Kentucky bluegrass or tall fescue. In these cases, the rings are not so distinct but instead has a very irregular appearance. Distinct lesions that are white or light tan with a light brown border can be seen on the affected leaves.

Yellow patch in a Kentucky bluegrass landscape

Yellow patch can be controlled easily with fungicides, but recovery can be slow if the turf is not growing due to cool temperatures. Early detection and treatment is very important for this reason.

Refer to the Disease Management Utility on TurfFiles for a list of recommended fungicides for yellow patch control.