If you will carefully look at the top photo above you will see a line about 1/2 way across my front lawn. The foreground is uninfested centipede sod. The distant area (which actually looks better in the picture) is heavily infested by torpedo grass. Photos taken Oct. 25th, 2009. The picture immediately below it is the same view on Dec. 5th after a bit of cool weather. The important part is the infested area has been treated with 2 broadcast sprays of Vantage. While the cool weather has caused all the grass to start turning brown, the torpedo grass is dying... or at least some of it is.
I've been fighting a torpedo grass invasion in my cedtipede lawn for almost 6 years. I live in southern LA (that's Louisiana, not Los Angeles, for those who might be confused). When we built our new home in 2003 the fill dirt was hauled in from behind the Mississippi River levees. Most of the dirt was OK, but some loads came pre-infested with torpedo grass, which was introduced in this area to control levee erosion (or so I've read). I put down centipede sod and everything looked great for a year or two, but gradually the torpedo grass came through and began to spread. I had no idea what it was and tried to control it initially by normal weed and feed process, pulling it up, and ignoring it. I soon realized that ignoring it was a mistake, but still didn't know what it was.
I began searching the internet to find help. After learning what it was I was dumfounded to discover there was nothing that could be done. Most advice consisted of humorous sugestions to "move" as a solution to avoid the stuff. The information did reinforce my own experience that it was very invasive, very aggresive, and very tolerant of flooding, drought, full sun, no sun, no matter what... it would grow just fine. It was also apparently resistant to any chemical treatment that wouldn't also kill my centipede.
In the spring of 2008 I stopped by my local County Agent's office to ask for help. He said basically the same thing I'd read on the internet, that there's nothing you can do. I went home discouraged, but a few hours later the agent called me and said that he had been contacted by a professor with the LSU ag center looking for test plots for a graduate student's work on torpedo grass. He asked if I'd be willing to allow them to use my yard. I quickly agreed.
The LSU people inspected the yard and agreed it would be a good test plot. They blocked off 2 areas in the worst infected areas of about 24' x 36' subdivided into 4' square blocks and marked with turf paint. They had a CO2 powered sprayer with a 4' wide head which sprayed evenly across the 4' blocks. It was about as scientific as possible for such an operation. Each block was sprayed with a different chemical, and some control blocks with nothing. Every 2 weeks they would record the impact of their efforts, then spray again. I was hoping the test might result in some control, but because most of the chemicals were ineffective not much was accomplished. I believe the paper was published, but I've never seen it on the web. The grad student left me a small bottle of the chemical he said was most effective. The name I thought he gave the chemical was clethodim (sp?) and that I could get it through a chemical supply house. I haven't seen a brand name weed killer with this active ingredient and don't have access to a chemical supply house. He said it would not completely control the torpedo grass but would stunt it and perhaps kill it back for 2 or 3 nodes. He suggested broadcasting it at a weak rate since it does damage the centipede also. The tips of the centipede grass would turn a dark reddish brown after application, but no permanent harm was done. It would kill the tips of the torpedo grass.
I had to stop my battle during the winter of 2008 since nothing was growing, torpedo or cendipede. In mid-summer 2009 I again began applying the clethodim, but ran out after 2 applications and honestly couldn't tell that it was doing anything. I wasn't yet ready to surrender to the infestation. Most of my neighbors have given up, or have never tried to get rid of the stuff, and maybe they are better off. But, I felt I had to do something. After the frustration with the clethodim I decided I would eat the elephant one bite at a time. I mixed up a small bottle of roundup at a stronger than recommended rate, borrowed one of my wife's paint brushes (you know, tiny ones for painting on canvas) and began my assault on the torpedo grass.
I started my "paint by number campaign" by dipping the brush in the roundup, then touching it to the ends of the torpedo grass around the outer edges of the infected area. Without going into detail, the method is effective and after several applications you can begin to drive the torpedo grass back. Of course if you accidently get some of the Roundup on the centepede you will kill it also. After sitting on the ground and bending over for hours just to cover a small area I would stand up and look at the huge infected area an get discouraged. The magnitude of the task seemed overwhelming. I just had to remind myself that if every day I killed more torpedo grass than it could grow that day, eventually I would win... if I lived long enough. As soon as I figure out how to do so I will post some pictures of the battle.
The only grass killer that seems to actually kill torpedo grass is roundup or the roundup generic equivalents, and it takes several applications to completely eradicate it from any area. Unfortunately Roundup is even more deadly to my Centepede grass. I had read on the internet that a chemical under the brand name Vantage could be used for control on centipede lawns, so I began searching for the product. I finally found a small container of the liquid gold at a feed & seed store and mortgaged my house to buy bottle.
I've applied Vantage to the infested area twice now and am encouraged by the results. Although the cold weather (it's December 2009 here now) has stopped the entire yard from growing, I was able to see the impact of the Vantage before the cool weather shut down everything. I'll also post pictures of that when I learn how to do so. With roundup herbicide, you get fast food results. Usually within 2-3 days you can see the torpedo grass beginning to turn yellow, but I've discovered the Vantage works much more slowly. The first indication that you've even sprayed the stuff comes 7-8 days later and the impact becomes more and more noticeable for 2-3 weeks. As far as I can tell it has not damaged my centipede as much as the clethodim, and without a doubt has impacted the torpedo grass more. The active ingredient in Vantage is sethoxydim and the bottle I purchased was distributed by Southern Agricultural Insecticides, Inc.. The name on the bottle simply says "GRASS KILLER contains VANTAGE herbicide.
You can read more about sethoxydim here: http://www.invasive.org/gist/products/handbook/19.Sethoxydim.pdf
