![]() ![]() In wet soils, there are a wide range of Pythium species that can infect roots, with some causing more damage than others. Why? Because it’s a complex interaction of root health and Pythium activity in the soil with summer stresses. OK, now Pythium root rot is a little more complicated to understand. Lucas who I will politely paraphrase as saying, “when it’s so hot and humid that your boxer shorts are stuck to your backside first thing in the morning, it’s time to treat for Pythium.” In any case, the gist of it is that hot plus wet equals Pythium blight, which equals rapid plant loss. Personally, I like the country wisdom of NC State’s Professor Emeritus Leon T. (3) the period of more than 90 percent relative humidity is greater than or equal to 14 hoursĪ rough (but useful) predictor of Pythium blight has been the 150 rule: when minimum daytime temperature plus maximum relative humidity is greater than 150, you are at risk for Pythium blight. Nutter, Ph.D., developed a model in 1983 as a research assistant at Penn State which predicts Pythium blight is likely to occur when all of these conditions are met: High night time temperatures and moisture favor the development of Pythium blight, and there are a few ways to predict outbreaks (some more scientific than others).įorrest W. The visual symptoms are small circular patches that have a distinctive orange color (the patches have coalesced to affect a large area). Pythium blight damaging a creeping bentgrass tee during the overly wet and hot summer of 2010. Pythium blight is most feared because it can cause widespread plant death in 24-48 hours with little chance of recovery. Pythium aphanidermatum, and a few other species that cause blight, are most active under hot, wet conditions. ‘greasy spot’ or ‘cottony blight’) is the most straightforward to understand and control. It is also why we see turf damage caused by Pythium diseases track with water movement, e.g., drainage areas, mowing patterns, etc.Īmong the Pythium diseases, Pythium blight (a.k.a. ![]() That is why a common factor in Pythium disease development is the presence of water or high moisture, e.g., wet, water-saturated soils or long periods of high humidity or leaf wetness. That is why most fungicides that control Pythium do not usually give control of other diseases.įurthermore, Pythium belongs to the Oomycota, which are called “water molds” for a reason: Pythium and other oomycetes need a lot of water to grow and reproduce effectively. ![]() Wong, Ph.D., Bayer CropScienceĪlthough we often classify Pythium as a ‘fungus’ it’s not a true fungus in the sense that it is actually in a different kingdom (Chromista) and, biologically, shares more in common with algae than true fungi that cause other diseases like brown patch and dollar spot (kingdom Fungi). Diseased turf will have an orange to black greasy appearance and will produce fluffy white mycelia after an overnight incubation in a moist container. Pythium blight is easy to identify and diagnose. Of the various Pythium diseases, Pythium blight and Pythium root rot are of the highest concern under high temperatures. Summer is here and hot days and warm nights can bring on Pythium as a major threat to cool season turfgrasses. Frank Wong, Ph.D., is part of the Bayer Green Solutions Team. ![]()
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