St. Augustine Decline and Palmetto

It looks like all the grass I planted in Sept. 2004 may be infected with St. Augustine Decline (SAD). What bad luck!

SAD is an untreatable virus that causes the grass to weaken and die away within a couple of years. SAD shows up as a mottled yellow appearance on an otherwise normal grass blade.

Last summer, I noticed some of my new grass had the mottled appearance. I didn’t think much of it because the grass seemed fine otherwise. This year, the temperatures are now warm enough for the grass to start coming back. Early last week, I noticed this same mottled appearance. After looking around, I noticed areas all throughout this new grass that has the mottled appearance.

Here are some pictures of this mottled grass:

I called my grass supplier to ask about this, and they were surprised. I spoke to the office manager and then the company owner, and both were certain that the variety I purchased, Palmetto St. Augustine, was as resistant to SAD as Raleigh. Palmetto is presented as being a step up from Raleigh on their site (link). In fact, the owner said he had a planting of Palmetto himself (not sure if it was in his own lawn?), so he was especially concerned. At first, he wondered if it could have been something else like gray leaf spot. However, I can find no other St. Augustine problem that matches the appearance in the photos. Compare for yourself: Google image search of SAD and an especially good, high resolution photo of SAD-infected grass.

The company owner promised that he or or his office manager would come out in the next few days and take a look at the grass. I put orange flags in the lawn to delineate a few significant spots of the affected grass. Each of the bright orange places is a flag:

This is just one section of the back yard. This problem shows up all over the new planting.

As far as I am aware, the only sure-fire treatment is to remove the grass and a few inches of soil and replace it all with new soil and grass. This is a major undertaking. I don’t look forward to this even if I don’t end up having to do it. It is possible to plant a SAD-resistant variety like Raleigh and hope it overtakes the existing grass as it dies out. However, by keeping the infected grass, I risk infecting the rest of my yard, which is almost 100% St. Augustine and which could be the SAD-susceptible common variety. (It’s quite possible that it is the original stand of grass from the 1950s. Raleigh came out in 1980.)

So far, none of my original stand of grass–the whole front yard and a little of the back yard–are showing any symptoms of SAD. This could be in part because I mow the front yard first, then mow the back yard. The mower sits for several days in a hot garage before it gets used again. If I was to transmit the virus anywhere, I think it would probably be to the small original stand in the back yard.

The fact that I have no SAD anywhere else eliminates my existing lawn as a culprit. Furthermore, neither I nor the previous owner use a lawn service, so there is no chance that this lawn picked up the disease from another lawn.

I really hope this is ends up being a false concern or a misidentified, treatable problem. I don’t want to go through a yard replacement.

4 thoughts on “St. Augustine Decline and Palmetto”

  1. I am having the same problem with St. Augustine grass I planted in 2010. I live in Arkansas. Of course, the people I bought the grass from said they have never had a problem with SAD. I too do not know how my grass got this problem since I cut my own grass and have never had a lawn service mow my yard. I have about 1700 square feet of this problem. I have noticed it in some other areas of my yard but it has not spread much yet. I will probably buy some Raleigh grass and plug it in different sections spaced out quite a bit and hope that it will spread and take over. That is the only thing that I have read to do for this problem. But like you, I do not want to have to do this cause it was hard work putting all this grass in to begin with and expensive. Since this was a post a few years ago, have you done anything about your problem and did it work. I would like to hear from you.

    1. There’s apparently nothing you can do about SAD except replace with SAD-resistant grasses. Probably about 1/2 of the new grass totally died out, and Bermuda has self-seeded in that area. The other half mainly exists in the more shaded parts, where I guess lower stress has allowed the grass to stay alive, possibly get through the SAD? I hope that if the grass has resisted the SAD, that it’ll eventually overtake the rest of the back yard again.

    1. I’m pretty sure it was SAD. The problem wasn’t present in adjacent, non-Palmetto St. Augustine, and the grass all eventually died out in the way that you’d expect for SAD.

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