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NOTE: Healthy grass requires sun. It requires a minimum of 4-6 hrs per day. Grass in shady areas will be weakened and more susceptible to a multitude of diseases & pests including TARR.
TARR (Take All Root Rot) has emerged as a major destructive disease for St. Augustine grass in Texas. Heavy spring and summer rains in recent years have contributed to the spread of this disease. The development of the disease is encouraged in well maintained lawns by the use of high nitrate nitrogen fertilizers as well as deficiencies of micronutrients in the soil. The causal agent is the fungus Gaeumannomyces graminis var. graminis. The brown-black mass of long branching growth of the fungus colonizes roots, stolons and shoots but it is primarily a root destroying pathogen.
Signs & Symptoms:
Symptoms of take-all root rot disease (TARR) typically appear on St Augustine grass as diseased patches of turf during late spring and throughout
the summer months. Typically this is seen as yellow patches. These yellow patches can persist throughout the summer growing season. This by itself is not indicative of the disease, as yellowing leaves can also be caused by cinch bug damages, certain nutrient deficiencies, or drought stress. Both TARR and drought stress will cause folding of the blades at mid rib.
As TARR progresses, you will see a thinning of the turf in circular or circular patterned patches one to fifteen feet in diameter. As the infected stolons die, ugly patches of bare ground are left and soon invaded by weeds. The lawn takes on an appearance of a “patchwork” of dead and declining turf. Any grass stolons attempting to grow into these barren areas will fail as they cannot take root.
TARR can be confused with brown patch as they look similar. The key difference being that with brown patch the leaves are rotted, but the roots are healthy. With TARR, the leaves remain intact while the roots are black, rotted and shriveled. These rotted roots / stolons can easily be pulled out of the ground. Thou grub damage can appear the same, the roots would be completely removed, eaten by the grubs, as opposed to being killed by the TARR fungus and remaining. TARR is seen more in shaded grass areas than in sunny grass areas.
Turf management vs. chemicals will help prevent and contain TARR. Fertilizers containing Ammonium (ammonium sulfate, urea, and ammonium chloride) are the preferred nitrogen sources. Fertilizers containing nitrate nitrogen (ammonium nitrate and calcium nitrate) seem to contribute to an increase in the severity of fungal diseases and should be avoided.
TARR has also been linked to a deficiency of manganese available in the soil. Ammonium nitrogen and / or chloride contain fertilizers will increase the amount of manganese in that is available to the plant. Raise the blades on your mower in the summer when the turf is already under drought stress. More leaf area supports the root system.
Manage your irrigation system, run it while you are available to make sure areas are not being over watered and the water is being absorbed not running off.
And follow this procedure to prevent the spread of the disease:
- Rake out all of the dead grass in the infected area and dispose of.
- Spread Canadian Sphagnum Peat Moss over the infected area
- Water the peat moss well to get it wetted and keep it moist.
- Spray Consan 20 (Triple action ammonium chloride, mix 2 tsp/gal of water) over the entire lawn. Repeat in 7-10 days.
- Apply South West Green Maker to fertilize the lawn.