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Mosaic Disease: A Threat to Floratam Lawns

Mosaic Disease of Floratam St. Augustinegrass is a major new viral threat causing death of this popular turf variety.  This winter, it is being increasingly noticed due to the colder weather inducing leaf blade symptoms.

Elongated spotting symptoms on Floratam. Photo UF/IFAS Schall

Floratam variety has been one of the better St. Augustinegrass varieties over the years, and probably comprises 90% or more of the St. Augustinegrass lawns in Florida.  Losses due to the mosaic disease (actually 2 viruses combined) have been severe, especially in the Boynton Beach and Wellington, Florida areas, and the spread continues.

The mosaic can also infect, but does not kill other St. Augustinegrass varieties, Bermudagrass, Bahiagrass, Paspalum and Crabgrass.  Zoysiagrass is not affected.

The viruses are mainly spread in the moist sap from freshly cut lawns on the wheels of mowers, blades, mower decks, and probably line trimmers.  Aphids may occasionally spread mosaic disease.  Floratam St. Augustinegrass weakened by the mosaic disease is much more susceptible to fungal problems like Take-all Root Rot and weeds.

What Can You Do?

Fungicides and other pesticides are ineffective against this mosaic.  No “vaccine” exists.

Replace dead or dying Floratam St. Augustinegrass with Bitterblue or Palmetto St. Augustinegrass varieties, or other resistant turfgrasses like Zoysiagrass, Bermudagrass or Bahiagrass. Additional St. Augustinegrass variety recommendations are likely as UF/IFAS research continues.

After mowing infected lawns, blow grass debris off equipment and wheels.  Then spray equipment until wet with one of the following disinfectants and allow to dry before using equipment on other lawns.

  • 2% solution of DuPont Virkon S disinfectant
  • 9 parts water to 1 part Household Bleach solution (5.25% sodium hypochlorite) Warning: bleach causes steel to rust

When possible, avoid mowing wet lawns.  Leaving clippings on infected lawns will not increase the spread of mosaic, nor will the use of reclaimed irrigation water.

For more information, see the link above, and the UF publication Mosaic Disease of St. Augustinegrass Caused by Sugarcane Mosaic Virus.

5 Comments on “Mosaic Disease: A Threat to Floratam Lawns

  1. This is great information. A virus like this can be devastating to our industry.

    • Thanks Donna:

      Please be aware that it is not a virus, but instead is a phytoplasma which is essentially a bacteria without a cell wall.

    • Doug:
      No fungicides are effective against this virus disease. In fact, the only control options currently are to avoid it, or replace the turf with a grass cultivar other than Floratam. – Bill

    • Hi Doug:
      The mosaic disease is not yet confirmed to be in St. Augustinegrass. Additionally, it is caused by a phytoplasma (bacteria without a cell wall), so fungicides likely would not be very effective.

      If you are asking about fungal diseases like large patch, take-all root rot, or gray leafspot that affect St. Augustinegrass, then we need to look at the specific fungal disease before fungicide recommendations can be made. Also, if you are not a professional pesticide applicator, most of the fungicides available to you are not very effective at minimizing lawn fungal problems. Your best shot is to try to properly mow, fertilize and water. I would suggest you contact your local extension office for the latest recommendations for lawn care in our area.

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