Lots o' Heat and Brown Patch

Well it looks like most of the country is in the grip of this heat wave now. We are working on day 29 of days over 100 F for 2011. According to the Oklahoma Climatological Survey map, we average approximately 15 days per year over 100 F. Our record is 50 days and we haven't even made it to August when we typically have our "hot and dry" weather. So….it is going to be a tough summer season again this year.

In our diagnostic lab we are getting a lot of creeping bentgrass samples with high nematode populations and/or suffering from good old summer stress symptoms. I predict that these issues are going to persist for us for the near future and putting greens will continue to become increasingly stressed. Remember, if you have that “big tournament” coming up and the membership is asking how fast they will be rolling, remind them to expect slow. The last thing you want to do during the weather we are having is try to make the greens roll ultra fast and throw a bunch of traffic on them when it is 105 F and the wind is blowing 25 mph! Again I say slow greens are better than no greens. Hopefully everyone has their smooth rollers on and they have reduced mowing as much as they can to manage plant stress. Be sure to have a good preventative fungicide program in place for Pythium diseases and brown patch.

Speaking of brown patch, we have a pretty good epidemic going on most of our research putting greens at the Turfgrass Research Center in Stillwater. Last week we had several evenings that we had humidity above 85%. For the entire month of July we have not dropped below 72 F at night in Stillwater. These conditions have been perfect for brown patch development. As most of you already know, preventative fungicide programs are the best strategy for managing the problem. So what is a good program for the Oklahoma area? Well, each year we conduct various dollar spot and brown patch trials on creeping bentgrass putting greens. These programs are often elaborate and often not cheap! Here are some brown patch data from our 2010 program trials. These trials were on a 'Penncross' putting green with a USGA sand/peat base located at our Turfgrass Research Center in Stillwater. Brown patch data were most severe on the July 16 rating, so I'll focus on that rating and on only the products applied up to that rating. You will find the products and the application dates in the table. Note that all applications were on a 14-day interval. For good control of both dollar spot and brown patch we don't recommend stretching your fungicide interval much past 14 days in our neck of the woods. Also, the DS ADVISORY treatment was an experimental exercise where we were targeting control of only dollar spot by advising sprays using a statistical model. Therefore, no brown patch products were applied resulting in high levels of brown patch.

So what happened? Well, highest levels of brown patch were recorded in the non-treated check plots with an average of 60% of the plot area symptomatic. Somewhat lower levels of brown patch were recorded in plots treated according to the ADVISORY program, but remember this program really doesn’t count when we are talking about brown patch control. All other plots treated with fungicide had significantly lower levels of brown patch and were not different from each other. Although, the OSU2 program had the lowest levels of brown patch (5% severity). Average turfgrass quality was lowest in plots not treated with fungicide and was considered unacceptable. Marginally higher levels of quality were recorded in plots treated by the ADVISORY. All other plots treated with fungicide had the acceptable levels of quality, however, the BASF1 and BAYER1 programs were a bit lower than the others. No symptoms of phytotoxicity were observed. So what this demonstrates is that if you start off with a good preventative fungicide program and make a reasonable decision about the products relative to the pathogens you expect to control, you will be reasonably successful at managing a disease like brown patch.