What it Actually Takes to get Pythium Blight on Creeping Bentgrass

Megan posted last Friday that hot, humid weather equals brown patch, which is absolutely correct! Our temperatures soared in the Midwest late last week and continue to stay hot and humid through this week. With the advent of hot, humid weather people started worrying about Pythium blight. Lane mentioned in a previous post (Summer fungicide programming) that many people spray for Pythium, but is probably a waste. Of course none of us believe that Pythium blight cannot develop, but the conditions that are required are so extreme that it rarely develops in shorter cut turfgrass.

For example, just this morning temperatures were well into the 80's and humidity levels were 90 % or more. Plus we have had over 4 inches of rain in the past two or three days. Of course everyone in the Upper Midwest has been worried about Pythium and are scheduling applications to control Pythium. Although we have diagnosed Pythium at a few courses, the extent of the damage is minimal. Symptoms appeared this morning on creeping bentgrass in close proximity to a drain in a fairway at a local Madison golf course. This particular area is also sheltered from air movement by a small pocket of trees. The picture in this post shows the extent of the symptoms, which basically amounted to a few small spots only in areas immediately adjacent to drains in fairways. The superintendent at this particular course is going to make an application of Subdue Maxx to clean-up these areas, but is not going to spray the entire fairways.

The other picture I have attached is from an area at the OJ Noer. This area was seeded with varieties of bentgrass earlier this spring. The plot is so wet that it could be considered a quagmire, but still symptoms are not that severe.

We are not advocating that Pythium is a problem of the past, but we are advocating that superintendents do not forget about other diseases. Brown patch can be very damaging in the conditions we are experiencing now, especially in fairways. If you have symptoms resembling Pythium blight or brown patch, have it diagnosed if possible. Both diseases can produced aerial mycelium and it has been our experience that brown patch is commonly mis-diagnosed as Pythium blight in the field.

As for other diseases, well the the stuff has definitely hit the fan. Dollar spot is raging on our plots at the OJ Noer and has developed at many courses we have visited. Brown patch has reared its ugly head at a few courses in the Madison area and Derek Settle has reported numerous cases of brown patch in the Chicagoland area. We have diagnosed take-all patch a few courses in Northern Wisconsin and it has developed at the OJ Noer. We will probably see a lot of take-all patch this year because soil temperatures were conducive for infection for a long time this spring. However, once take-all symptoms develop a fungicide application will not help alleviate the symptoms. Areas affected by take-all patch will need to be "nursed" through this warm spell by hand watering and possibly a light fertilizer application.

The weather in the Midwest continues to amaze me. Last week we were still measuring soil temperatures in native soil areas at 65 F. This week air temperatures soared up into the middle 90's during the day and nighttime temperatures in the upper 70's. Reminds me of North Carolina weather. Relief is on the way, as forecasts are predicting a slight cool-down this weekend. I think I may have to enjoy some beer and cheese curds!