Fall is finally starting arrive in the central portion of the US. Lubbock ended up going approximately 12 weeks (first week of July through third week of September) with no measurable rainfall. Things got pretty dry during that period, and there was a lot of warm-season grass in town going into drought-induced dormancy if not irrigated. Needless to say, those environmental conditions are not favorable for many diseases to occur. The air temperatures are currently fluctuating highly with the first couple of days this week being in the 80’s and 90’s for highs; however, there is a nice cool front pushing really cold weather down this way.
I seeded an overseeding trial at one of our local golf courses in mid-September just prior to that rainfall event that we had to break the long streak of no rain. The irrigation level and frequency was turned up in the portion of the fairway I overseeded to ensure we could get good germination and growth from the varieties planted. Additionally, I applied 1 lb of fertilizer at the time of seeding, and the entire golf course was fertilized just a couple of weeks later. The increased fertility, additional irrigation, and slightly lower temperatures resulted in the development of large patch symptoms. I started noticing the small patches of thinning turf and a slight orange color on October 5 (Image 1). As the bermudagrass is starting to slow down a little to prepare for dormancy, the conducive environmental conditions and presence of the caused the symptoms to pop very rapidly (Images 2 and 3).
I have not had an opportunity to go around and see many other parts of the golf course to know if this is primarily confined to the area I overseeded. It is highly likely due to the additional irrigation being applied to ensure the seedling plants are receiving ample water. Ultimately, this disease will not reach a severe enough level to warrant a fungicide application at this golf course or in this region. However, if you are in a more humid region of the country and managing zoysiagrass or residential lawns with St. Augustine or centipede grass, you may see a large benefit in applying a fungicide to slow the production and spread of R. solani. It is also important to avoid cultivation practices when active patches are present to reduce spread of the pathogen.
It is important to understand that many of our turf diseases like to infect turf that is under a little environmental or physiological stress, so our warm-season grasses are prime targets for fungal pathogens as they prepare for dormancy in the near future. One of those fungi that is not going to result in symptoms now, but you can bet it is feeding on your grass is Ophiosphaerella spp. This is the fungus that causes spring dead spot on bermudagrass. If spring dead spot is a normal problem you face each year on the turf you are managing, it is time to get the fungicide application out very soon. It is best to get two applications down before the first freeze, apply in high water volumes, and water in the product to move it into the soil.