Lubbock, TX has seemed to turn into Scottland or the Pacific Northwest randomly over the last few weeks. We received about 4.5 inches of rain the first week of May, a little over 2 inches last week, and about half so far this week. The forecast continues to call for rain through the weekend and into next week. In addition to the rainfall totals, we have accumulated recently, the high temperature in Lubbock the last two days has been 55°F. Needless to say, bermudagrass is basically just hanging out with nothing to do when the temperatures are that low.
Not scientifically but completely observationally, I find the limited symptom expression on ‘Celebration’ bermudagrass in my yard compared to the standard common bermudagrass to be interesting. I seeded my yard with ‘Riviera’ bermudagrass last summer, but I had much more success growing pigweeds in places instead of grass. The coverage was not sufficient toward the middle of the summer, so I sprigged Celebration into weak areas and sodded it around the back of my fence. The difference in color and growth rate alone under these environmental conditions are pretty clear (Image 2). The combination of low temperatures, lots of rainfall, and extremely cloudy conditions over the last 2-3 weeks has provided excellent conditions for leaf spot of bermudagrass in my backyard. When I got home a couple of days ago, we had not really had any rain, but there was guttation water on all the leaves at 5 or 6 in the afternoon. That was also the first afternoon I started really noticing how much leaf spot was present in the backyard and the significance of the infection (Image 1).One of the reasons for the variation in color may be the infection of the common berrmudagrass with leaf spot fungi. The severity of leaf spot symptoms on the common bermudagrass are much more significant with necrosis and lesions observed on leaf sheaths (Image 3). This could quickly lead to the “melting out” stage if the crown material is impacted by the fungal infection. Alternatively, the Celebration only has small, purple leaf lesions only (Image 3). The symptoms will likely continue expanding if conditions remain favorable for disease development, but I don’t suspect Celebration will exhibit the severity of symptoms observed on the common bermudagrass.
The variation in symptom development is very similar to research that I was able to help with as a Master’s student at Mississippi State University working for Dr. Maria Tomaso-Peterson. In that case, we were evaluating leaf spot severity on seven different seeded bermudagrass cultivars at four nitrogen rates. To see more about that research, you can visit the following website: https://dl.sciencesocieties.org/publications/ats/abstracts/7/1/2010-0326-01-RS