Pest Alert № 9 — Pythium Root Dysfunction of Creeping Bentgrass

It’s that time of year in Chicago. One of the things you realize when you get to the upper Midwest (the Great Lakes to be exact) is that it can get wet. When does it see the most rain? Well it turns out to be in the months of July and August. That should tell you something about how to grow healthy turfgrass — in the summer — in Chicago. You will need good drainage.

The D word of drainage cannot be overstated because we use creeping bentgrass extensively from tee to green. And on the edges? Trees which restrict air movement which lessens natural evapotranspiration (aka ET, I’m not talking about the 1980s movie). So if you do not have drainage and you have trees = drying out can be near impossible when humidity levels are high. That’s right now in Chicago.

If you do not have good drainage you are going to get in trouble each and every summer (unless there is a drought). Droughts in Chicago are infrequent. What is more frequent? Flooding on occasion. This story is about golf greens and DRAINAGE. Actually this is mainly about ROOTS. Here goes

Cultural Practices. Pythium root dysfunction is caused by multiple Pythium species that reduce normal root function. Anything that can reduce stress will help to mask symptoms (thin patches). Raise the mowing height. Be ever-conscious of rotating equipment traffic on greens. Golfer foot traffic usually is a major interaction = creates the patches near flag/pin placement. Fertility via roots may not work and so liquid foliar options become important. PGRs are not needed when plants are not growing midsummer and obviously PGRs may limit recuperative potential even more.

Chemical. Current fungicides for Pythium have greatly improved over the years. Aliette was an important fungicide as it was the 1st systemic Pythium fungicide of its kind. Today there are many systemic fungicide options in the Phosphonate Group. All are very useful to help suppress Pythium root dysfunction. Other options include Pythium specialists such as Banol, Subdue MAXX, Segway and others. Read the label. Water in immediate to the depth of roots as may be needed. In other words know the plant part you are targeting.

Chemical Control of Turfgrass Diseases 2020. Use this guide. An excellent resource for Pythium root dysfunction and most other important turfgrass diseases. http://www2.ca.uky.edu/agcomm/pubs/ppa/ppa1/ppa1.pdf

Image 1. This could be anything and so one needs to rule out things. The list goes something like this: Nematodes, anthracnose, summer patch (if Poa annua is in the mix). I checked off my list and what did I find? Pythium root dysfunction in a Penn A4 creeping bentgrass green during a wet Chicago summer. Settle, Aug 17, 2021

Image 2. Can you see the soil core samples? I did that. The patches come and go and that is the other part of the story. Without healthy roots the bentgrass plants cannot maintain normal density. Older lower leaves are senesce/drop off. The turfgrass isn’t entirely killed. But when humidity levels drop and there is wind = look out. Midday wilt watch of greens is a critical practice for superintendents and staff. Settle, Aug 17, 2021

Image 3. Closeup of thinning caused by chronic Pythium root dysfunction. Can you guess when symptoms began? It was the 1st flooding event of summer or about the third week of June. Thereafter, Pythium fungicides can only provide limited control on this green and a couple others. Why? Internal drainage isn’t working properly. The real fix is to invest in and improve drainage. Settle, Aug 17, 2021