| How is Pythium misunderstood by superintendents? The number one misconception about Pythium is that it’s caused by hot and wet conditions. That’s true of Pythium blight, but not Pythium root rot. In other parts of the country, there’s Pythium blight, but here in North Carolina, there’s a lot of Pythium root rot and root dysfunction. I see a lot of supers spraying for Pythium blight when the need to be more focused on the rootzones, and not so much on foliars. Root rot has been the disease that’s been the most problematic in the last two years, with heavy rainfall and wet soil conditions. Temperature really has nothing to do with it. It’ll start as early as March or April, and you can see it as late as October. It’s driven by wet soil. Many golf course supers don’t worry about Pythium until June and July. The supers have no fungicide protection up to then. What made the Pythium outbreak so damaging last year? A lot of our catastrophic failures of bentgrass greens last summer traced back to cases of Pythium root rot in May of last year. It hit throughout, we had heavy wet conditions in May, which gave the Pythium the chance to come in. Then the weather followed up with a lot of continued stress and high heat, and we lost whole greens. We’re concerned that we may be setting up for a very similar situation because the weather has been the same through this year. We’ve tried to send out alerts and let supers know that basically, if they’ve had root problems in the past, they need to make a preventative fungicide to protect their roots. How do you recognize Pythium on a course, and how do you stop it? The problem with Pythium is that it’s a very difficult organism. They’re not actually fungi, and there’s not much overlap between them and other pathogens as far as fungicides. The symptoms are very different. Pythium blight is easy to diagnose, but root rot is extremely difficult to diagnose. I can’t diagnose it all the time in the field. Unless you diagnose it with a lab, you’re just guessing. Money is really on the line here with Pythium, so it’s worth spending for a correct diagnosis. Look for irregular areas of rapid dieback of foliage and a shallow root system that’s tan in color, a weak root system overall. On occasion you’ll get very distinct patterns, but not usually. If you see something that’s looking like that, you need to act pretty fast. A lot of times there’s a lot of damage that’s occurred at the roots when the symptoms start to show up. When you do see it, be sure not to over-irrigate the area. For a lot of supers the tendency is to try to solve a problem with irrigation, when in reality it can make the situation much worse. Check your soil moisture levels. If there’s moisture in the soil, don’t put any more water down. In fact, that’s a good quick diagnosis in the field. The biggest way to avoid it is with good soil drainage. Soil moisture monitors help monitor the water content of your profile – something like that can help avoid problems with Pythium. What about the other forms of Pythium? Pythium root dysfunction is another different pathogen. It’s really only related in that it’s caused by a species of Pythium. It’s got very different start and stop times. It attacks roots in fall and spring when the roots are growing in. Essentially when you end up with is a plant that has very little stress tolerance. By time you see the symptoms, the damage is already done. There’s a duration of leaf wetness and high temperatures – when it’s wet in the evening and the night temperature stays around 65 degrees – that’s when Pythium blight is most active. Pythium blight can be a significant threat on annual bluegrass putting greens. It can also damage perennial ryegrass, annual bluegrass or creeping bentgrass fairways. But it is not a common problem on creeping bentgrass greens. Superintendents managing bentgrass greens throughout the transition zone should be focused more on the root-infecting Pythiums than the foliar blight. Fall and spring are the best times to prevent, but it really all comes back to drainage. Fixing the drainage will save you from a lot of headaches down the road when it comes to Pythium. |