Take All Root Rot (TARR) is a serious fungal disease attacking the root systems of warm-season turfgrasses, particularly St. Augustinegrass, Zoysiagrass, and Bermudagrass. The pathogen, Gaeumannomyces graminis var. graminis, is a soilborne fungus that compromises the grass’s ability to absorb water and nutrients. This leads to the decline and eventual death of the turf. TARR is manageable through a combination of timely cultural and chemical strategies. This guide provides actionable steps to treat an active infection and implement long-term prevention measures.
Identifying Take All Root Rot
The initial sign of TARR appears as irregular, yellow-brown patches in the lawn, ranging from a few inches to several feet in diameter. Since TARR is a root infection, the above-ground symptoms are secondary to underground damage. The grass within these patches may appear thin and wilted, sometimes showing a distinctive bronze or “neon yellow” discoloration at the blade tips.
A definitive sign of TARR is that affected grass is easily pulled up from the soil because the root system is severely compromised and decayed. When examining the roots, stolons, and rhizomes, you will notice a characteristic darkening, turning them black or dark brown instead of the healthy white color.
The fungus thrives in wet, stressed turf, particularly in soils with poor drainage, excessive thatch buildup, or an alkaline pH level above 6.5. The disease is often most active during periods of moderate temperatures, typically in the spring and fall, when soil temperatures are between 77° and 85° Fahrenheit.
Immediate Cultural Management Strategies
Immediate adjustments to your lawn care routine are the first line of defense to stabilize the turf after confirming a TARR infection. The primary goal is to reduce moisture and plant stress, creating an environment less favorable for the pathogen to multiply. This begins with a complete overhaul of your watering practices, shifting away from frequent, shallow irrigation which keeps the surface soil wet.
Water deeply and infrequently, aiming to wet the soil to a depth of about six inches only when the grass shows signs of moisture stress. Irrigate early in the morning, ideally between 4 a.m. and 6 a.m., allowing the leaf blades and soil surface to dry completely before nightfall. Allowing the turf to remain wet overnight significantly encourages fungal growth and spread.
Raise the mowing height on your lawnmower to the highest setting recommended for your specific turfgrass type. Taller grass blades increase the surface area available for photosynthesis, providing stressed roots with more energy for recovery and growth.
The fertilization strategy should also be modified to provide necessary nutrients without overwhelming the stressed roots. A foliar feeding application of a light, quick-release nitrogen fertilizer can supply nutrients directly to the leaf blades, bypassing the damaged root system. Avoid heavy, single applications of fertilizer, especially those high in nitrate-nitrogen, as excessive nitrogen can promote lush growth that the compromised roots cannot support. Applying micronutrients like manganese in a sulfate form can also help the plant fight the disease.
Chemical Treatment Options
While cultural practices provide the necessary environmental correction, fungicides are often required to halt the active progression of TARR and protect the remaining healthy roots. These chemicals work best when applied early in the disease cycle, acting as a supplement to proper maintenance, not as a standalone cure.
Look for systemic fungicides containing active ingredients such as azoxystrobin, propiconazole, myclobutanil, or thiophanate-methyl. These compounds are absorbed by the plant and translocated internally, allowing them to attack the soilborne fungus within the root zone. Fungicides are most effective when applied during the spring and fall, coinciding with moderate soil temperatures when the fungus is most active.
Proper application is essential for success. Systemic fungicides must be watered into the turf immediately after application, typically with about one-eighth to one-quarter inch of irrigation. This irrigation is necessary to move the active ingredient from the grass blades down to the root zone.
To prevent the fungus from developing resistance, rotate between products containing different active ingredients throughout the treatment period. Always ensure the selected fungicide is specifically labeled for residential lawn use and for controlling Gaeumannomyces graminis.
Long-Term Soil Health and Recurrence Prevention
Preventing TARR recurrence involves addressing the underlying soil conditions that allow the fungus to thrive, focusing primarily on lowering the soil’s pH level. Since the pathogen favors alkaline soils (pH above 6.5), the long-term goal is to maintain a slightly acidic range, ideally between 5.5 and 6.0. Correcting the soil chemistry helps suppress the fungus and strengthens the turf’s natural defenses.
The most common and effective material for this purpose is a thin topdressing of peat moss across the affected areas. Peat moss naturally has an acidic pH. Spreading a layer about one-third of an inch deep helps to acidify the surface soil and provides beneficial organic matter. Following application, the peat moss should be lightly watered in to move the material down to the stolons and runners.
Another soil amendment option is the application of elemental sulfur, spread at a rate of three to five pounds per 1,000 square feet annually to gradually lower the soil pH.
Structural improvements to the soil are also necessary for long-term health. Regular core aeration helps alleviate soil compaction, which improves internal soil drainage and increases oxygen flow to the roots. Improving drainage permanently prevents waterlogged conditions that stress the grass and encourage TARR development. A comprehensive strategy combining soil acidification, improved drainage, and ongoing cultural adjustments is the most effective approach to ensure the disease does not return.