Major construction on our new Plant Disease Clinic at the Gainesville campus of the University of Florida finished up in December last year. We were given a date for the dedication and ribbon cutting of April 25th, and since this lab houses the Rapid Turfgrass Diagnostic Service, I decided the turf in the landscape needed to look good for all the admin and visitors that would be there to tour the facilities. In our IFAS recommendations, we discourage sodding warm-season grasses in the winter because the potential for growth at that time of year is slim to none. Desiccation and low temperatures often lead to sod failures, or a weakened, problematic, spring green-up at the least. In fact, the regional utility company was putting down small sections of St. Augustinegrass sod throughout my neighborhood at this time after trenching and laying new cables. 75% or better of that sod in several small “plots” I walk past routinely is dead and being invaded by weeds.
My solution was to seed the roughly 10,000 sq ft turfgrass area with perennial ryegrass. I first purchased Journey intermediate rye and seeded at 15lbs/M. Two big rains later, I reseeded with Allsport turf type perennial ryegrass at the same rate, primarily covering areas where the seed had been washed away. By the end of January, we had a good stand of ryegrass that looked great. Dr. Jason Kruse and staff of the Turfgrass Envirotron next door mowed the grass and made two fertilizer applications for me (thanks Jason!). Now I just had to keep it alive through the end of April.
I saw very little disease in the stand through an uncharacteristically cool March for Central Florida. One week prior to the ribbon cutting ceremony, I noted some small patches of stressed turf on the shady side of the building where dew persists longest. Temps the week of the 14th broke into the upper 80’s for highs and 60’s for lows. Rain was predicted over the weekend, so I made an application of Hertiage TL, Prostar, and Signature with chemical surplus from trial work (that needed to be used up) on that Friday. I was targeting pythium blight, brown patch and gray leaf spot in a “shotgun” app of some very good products. It did rain all weekend, and an unsprayed plot of bermudagrass overseeded with intermediate ryegrass lost 65% of the cool-season canopy that weekend. Our 10,000 sq ft area still looked great, however, for the dedication and ribbon cutting on the 25th.
Fast forward three weeks to today. No more fungicides have been applied, and sod will be ordered in the next week. Those stressed areas on the back side of the building, nearest the irrigation heads are now showing 5 to 7% gray leaf spot severity. The longer, unmowed border has the most impressive symptoms with typical lesions, “fish hook” twisting, and gray felty sporulation. Close inspection of the grass blades in most any part of the lawn show some tip dieback and a few small lesions, although the overall turf quality is still quite acceptable. I must admit that while I was excited (pathologists are sick you know) to see my old friend Pyricularia under the microscope this morning, I also know that this is the beginning of what will be a rapid end to the nice ryegrass lawn that I have thoroughly enjoyed seeing every morning as I arrive to work.
In a couple short months, the pathogen will make its way north to the Midwest and Mid Atlantic by wind dispersal or will emerge on golf course fairways and roughs from greatly reduced populations that have survived locally. In either case, gray leaf spot is a disease that managers of perennial ryegrass should be on the lookout for, keeping in mind, the pathogen is alive and well currently assisting us with spring transition from ryegrass to our C4 grasses here in Florida.