Golf Course Industry asked Dr. Brandon Horvath, assistant professor, Department of Plant Sciences, University of Tennessee for his thoughts on large patch (rhizoctonia solani) pressures and control for this year.
Do you expect any additional pressures from large patch due to the more extreme weather that so much of the south experienced this past winter?
I don’t think the kind of winter we had will be as much of a factor as the spring and summer we will have. The pathogen was probably not active under the very cold temperatures. If we have a more moderate spring with wet weather, we’ll probably see more activity. The cold weather could break up the season into a more pronounced spring season and a fall season.
What should superintendents be watching for?
The first things to be aware of are soil temperatures and weather conditions. A coupling of soil temperatures in the mid-60s, specifically 65 – 70 degrees, with warmer, wet days provides the optimum growing conditions for large patch. Regularly monitor soil temps especially as you hear forecasts for rainy days. I’m not talking about the occasional rain, I mean full days of cloudy, wet weather that is going to keep the turf and the soil moist to wet for an extended period of time.
What should the superintendent do when those conditions are forecast?
It is time to get the preventive sprays down. Prevention is much more effective than trying to cure the problem. Hopefully, preventive applications were also made last fall. There are numerous products on the market, and more coming. Talk to your university researchers, company representatives and read labels to help you decide what is best for your area. You will want to follow-up with a second application in 14 to 21 days depending on the product you use. And, of course, remember to get your applications down this fall.
What should we look for besides that or if we get rainier weather than was forecast?
This year it is especially important to distinguish between large patch and winter kill. Large patch is usually going to appear in circular patterns. The earliest indications are a brownish tan discoloration as the rest of the grass is greening up. If the pathogen becomes very active the coloration may appear orange or salmon. Ideally, treatments will be applied before it gets to that stage. Winter kill will usually be larger, more non-descript patterns of dead turf. If the problem is winter kill, you’ll need to sod or sprig depending on the type of grass you have. If the problem is large patch, you’ll need to be more aggressive as once it appears, it is going to be harder to stop.
Anything else superintendents should be aware of?
In the deeper south, especially around Atlanta and beyond, there is quite a bit of Zoysia matrella. It behaves a little differently than Zoysia japonica. Some feel that japonica is more susceptible to large patch but the disease is more visible on the matrella because of the density of the turf. Those with matrella may want to keep a closer eye on the weather and get on a preventative program a little quicker.
