Take-All Root Rot: Symptoms And Control

St. Augustinegrass is a traditional feature of Florida’s lush landscapes. However, this popular sod grass is now threatened by take-all root rot that has spread through the sod fields and lawns of the South from Florida to California.

The phenomenon is linked to a fungus that inhabits the soil called Gaeumannomyces graminis var. graminis. Damage caused by this fungus normally occurs from early spring through late summer.

Signs of take-all root rot include yellowing or lighter green patches on the lawn, roughly circular and from 3 to 15 feet in diameter. As the season progresses, all the grass in the patch may die, leaving only bare ground populated by weeds. The syndrome is normally most conspicuous in sun-exposed areas with shaded grass less susceptible. In climate zones where St. Augustinegrass does not go dormant seasonally, the grass will often appear to recover during the winter months, only to have the symptoms recur the following summer.

In any plant, root rot impacts the roots and degrades its capacity to absorb water and take in critical nutrients from the soil. For take-all root rot to thrive, three conditions must coincide: the presence of Gaeumannomyces graminis var. graminis, a host plant such as St. Augustinegrass, bentgrass or bermudagrass and a typical southeastern U.S. climate, particularly during a year of high rainfall.

Methods that combine attention to lawn care as well as use of fungus control chemicals may be effective in preventing or controlling take-all root rot in South Florida:

• Raise the height of the lawn mower during times when root rot is most prevalent.
• Follow a balanced program of fertilization including application of high levels of potassium.
• Apply slow release nitrogen.
• Consult a landscape professional about application of fungicides to areas of the lawn are already damaged as well as the turf immediately surrounding those areas. Fungicides approved for root rot control include azoxystrobin, propiconazole and triadimefon.

Haggerty Pest Service has served South Florida since 1985. Our professional landscape work includes a variety of services to preserve the outdoor environment of Palm Beach and Broward County residents.

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