Reduced Growth Potential
Things are different in Florida. For turf managers, winter generally means a time for family, meetings, and brushing up on the latest and greatest new products to incorporate into the management plan for the coming season. South Florida (I4 corridor and south) contains the majority of the golf courses in our state and has a different outlook. Winter is the peak season for golf and can be a tough time for bermudagrass putting greens, tees, and even fairways. Warm-season grasses tend to coast through “winter” by going dormant, slowing growth, and/or utilizing carbohydrate reserves that were stored when temperatures, day lengths, and light intensities were ideal for C4 photosynthesis. Winter in South Florida isn’t cold enough for dormancy, and in years with regular rains and higher than average temperatures, turf pathogens take advantage. With reduced growth potential, the most difficult to manage disease issues occur on greens already running without a full “tank” in reserve either due to prior summer and fall disease or nematode problems, juvenile growth due to aggressive fall nitrogen use, or some other issue.
Pythium in January? I’ve seen it all.
During the 2013 Christmas break a handful of top notch superintendents contacted me with disease concerns. Some pictures of symptoms on the ultradwarf putting greens made me think two distinct possibilities were likely. First could have been leaf and sheath spot disease caused by R. zeae. There were distinct patches (Fig.1) with profuse fuzzy hyphae being produced on the leading edge of patches after the super incubated a cup cutter core in a ziptop bag with moist paper towel in the bottom (Fig 2). Looking on my cell phone at the pics the super had sent, I was now leaning toward the second of the two likely possibilities—Pythium blight. We do see the disease in South Florida on Bermudagrass in the winter, and though it occurs less frequently than on overseeded Poa triv. or bentgrass, it can be nearly as devastating when it does occur.
Figure 1. Patches of Pythium on a golf course putting green in January.
Figure 2. Mycelium on the turf sample following incubation.
…and then the resistance.
I got off the plane from visiting family in Indiana and went in to the after-hours cooler at the Plant Disease Clinic. UPS wasn’t running the route, even though after-hours delivery had been requested. In any case, I got the samples on the 2nd and was able to confirm the Pythium blight diagnosis by looking at the hyphae that had formed on the plug in transit. I also knew that the super had sprayed with a single site mode of action fungicide specific for Pythium, based on the suspected diagnosis, so I plated the blighted turf on a medium amended with that fungicide to test for resistance. Sure enough, the Pythium blasted through the fungicide in the plate, and another email went out on the 3rd prompting another application with a different mode of action.
Overall it was a good start to the year. The patches were halted while fairly localized, and I was happy to hear from a couple of those superintendents at an Everglades Chapter GCSAA meeting the following week, that things were looking up, and symptoms had been arrested, despite favorable conditions continuing for another 10 to 14 days. Were not always able to help, but samples 1 and 2 for the year made a difference for a superintendent—I hope we’re able to continue that trend through Christmas break 2014.