Take-All Root Rot Information
Causal Agent(s)
- Gaeumannomyces graminins var. graminis
- Gaeumannomyces graminicola
- Gaeumannomyces nonograminis
- Gaeumannomyces floridanus
- Candidocolonium cynodontis
- Magnaportheopsis cynodontis
Hosts
- Hybrid bermudagrass
- St. Augustinegrass
Symptoms & Signs
Stand symptoms of TARR manifest as chlorotic patches 8-24” in diameter. Left untreated, patches will begin to thin out and eventually become bare. In early stages, roots appear off-white in color with black lesions. As the disease progresses, roots are shortened and are black and rotted. Stolons and rhizomes may become infected and turn black and rotted as well. Under a microscope, dark ectotrophic hyphae can be seen on infected roots. These pathogens also produce characteristic lobed hyphopodia that are used for attachment and penetration into host tissue.
Images of TARR symptoms:
When Does it Occur?
TARR is most common in the fall, winter, and spring but can occur any time of year when turfgrass is stressed. Optimal soil temperature for pathogen infection ranges from 77-86° F depending on the predominant pathogen at your site. Prolonged periods of rainfall are conducive to disease development. Excessive thatch accumulation, excessive soil moisture, ultra-low mowing heights, low fertility, and excessive growth regulation can all predispose turfgrass to TARR development.
Cultural Management
Alleviate plant stress during poor environmental conditions for warm-season turf. Increase mowing height and decrease frequency. Dilute thatch accumulation via aerification and light, frequent topdressing. Verticutting may not be advised during favorable disease development conditions because the pathogens may infect stolons and rhizomes. Manganese may reduce disease severity and high soil pH may exacerbate disease, but research in turfgrass is lacking.
Chemical Management
All fungicide applications should be made preventatively for best disease management. Once above-ground symptoms are observed, the root system is already compromised, and curative management is difficult to achieve during reduced growth periods. Begin fungicide applications when soil temperatures are between 77-86° F and continue applications until conducive conditions subside. Fungicides need to be immediately watered-in with at least 1/8” water to drive products into the rootzone, where the pathogen is active.
