Once again Mother Nature has thrown the Southeast a curve ball with regard to weather. This summer has been fairly mild and when temperatures did rise, relative humidity and rainfall were minimal. With two moderate summers in a row we start hearing about experimentation in fungicide programs, especially on creeping bentgrass. Admittedly there are great new products on the market, but the staple for creeping bentgrass putting greens in the Southeast has been Chipco Signature (4 oz./1,000 ft2) + Chlorothalonil (3.2 oz./1,000 ft2 for Daconil Ultrex). Mancozeb can be substituted for chlorothalonil as well, but keep in mind that new seasonal limits and maximum use rates apply. Be sure to consult the most recent labels prior to use. We have known about the beneficial effects of mixing these products for a long time. My predecessor, LT Lucas showed this in the early 80s. New fungicides have come along and the new ads are interesting and sexy, but the bottom line is if you have been successful with Chipco Signature/chlorothalonil mixtures then stick with it. It works and has profound effects on plant health. The image shows a program by Quali-Pro (A in image) and BASF (B in image), and they both look great. One relies on fosetyl-Al + chlorothalonil + Foursome and the other a nice rotation of chemicals including BASF’s Intrinsic technology and Chipco Signature + Daconil. My job is to examine them side-by-side and present the results. Your job is to take those results and make a decision that fits the expectations and budget of your golf course. I am convinced that a phosphite + chlorothalonil + pigment (either pre-mixed or mixed separately) should be the backbone of a fungicide program on creeping bentgrass in the Southeast.
Based on diagnoses in our lab, the other major issue on creeping bentgrass is Pythium root rot. We have a small study at the Lake Wheeler Turfgrass Research Lab that has root rot and Segway (0.9 fl oz/ 1,000ft2 ) or Segway mixed with Disarm (0.36 fl oz/1,000ft2), Insignia (0.7 fl oz/1,000ft2), or Heritage (0.4 oz/1,000ft2 ) are providing the best disease control. We did not examine all intervals or all combinations because root rot is extremely difficult to work with. We are exceptionally fortunate this disease developed at the farm, so we can provide some hard data to support our recommendations. We have recommended Segway in the past, but we also advocate rotating products like Banol, Stellar, and Subdue MAXX into the program as well. Our study is LIMITED in scope, as we only tested 21 day intervals. The results clearly show that Segway or Segway mixed with the QoIs listed above, suppress Pythium root rot for 21 days. I think our results do indicate that Segway could be a nice starting material for preventing Pythium root rot. However, it is CRITICAL to initiate preventative applications in mid to late May to be successful. Rotating chemicals like Subdue MAXX, Banol, Terrazole and Stellar are necessary to prevent resistance issues and only three applications of Segway at 0.9 fl. oz./1,000ft2 are allowed in a season.
Things have been relatively quiet in the diagnostic lab. We had a couple weeks of intense sample submissions, but that was only a few weeks. We have seen Pythium root rot (which is a perennial submission to our lab), Rhizoctonia zeae on creeping bentgrass, etiolation, yellow spot, nematodes, summer patch and as usual numerous abiotic issues. Remember, people rarely send us disease samples that are easy to diagnose in the field such as dollar spot, fairy ring, brown patch, etc. Just for perspective, we have received about 4,000 turf samples in the past eight years. Of those, 52% did not have a disease. Just because turf declines in the summer does not mean a fungus, nematode, or bacterium is to blame. Many times the grass cannot handle the stress (mechanical, chemical, or environmental) and thus dies. The lesson here is to use a reliable diagnostic lab prior to applying large amounts of fungicide when turf starts declining.