Khaki Weed

“Devil weed”, burr weed, or just “that little, flat weed with round, thick leaves that forms a carpet of little round stickers” – all describe the little pest called Khaki weed, (Alternanthera pungens).

Homeowners and pet owners have called our AgriLife office seeking help as they no longer allow the children or pets outside because of the painful little stickers.

You will find it outside in many places.  With warmer temperatures and the rain we have had, seed germination has been good.  The whole point of this column is to encourage you to be vigilant and be ready to spot it and then treat it before it takes over your yard. If you already have Khaki weed, maybe you will gain a tip or two that will help keep it at bay.

Dr. Matthew Elmore, Extension Turf Specialist in Dallas says there is little to no research on this weed in the USA, although one study has been done on controlling it at Texas Tech and another in Arizona.

Since there is little research on it, and no herbicides in the U.S. currently are labeled for it, what do we do? Dr. Casey Reynolds, Extension Turf Specialist in College Station indicates we should try herbicides that contain a combination of: 2,4-D, MCPP, MCPA, carfentrazone, dicamba, metsulfuron, triclopyr, and/or fluroxypyr. Glyphosate is listed as well, but it will kill nearly everything you spray. Bear in mind these are all post-emerge herbicides, meaning they primarily impact live plants and not seeds. READ THE LABEL of whatever product you choose.

For those willing to try a pre-emerge herbicide earlier in late winter and early spring, Elmore says the active ingredient isoxaben might be worth a try. This will take some water or light tillage to incorporate into the soil as pre-emerge products only work on reducing seed germination. The herbicide label will provide details for that product.

Extension News

If you are opposed to chemical control, I suspect a layer of mulch could really cause it to struggle. Although there is no research to back this up, I am confident that when I raised my mower deck to three or four inches where I did have some grass, the Khaki weed had to grow vertically to compete and then it became thin and had almost no horizontal runners. Many have told me they repeatedly scalped their lawn and Khaki weed loved it when it can grow low and flat.

Because there is such limited research, here are a few tips that seemed to work this past year. First and most important, be ready to spray about four to five days after every rain event if you see small Khaki weeds.  Spraying 2, 4-D alone will show little results, so use combination herbicides.  The key to tough weeds like this one is you have to be persistent.  You may have to spray multiple times.  If you choose glyphosate, it does kill everything you spray with it, so you may have to sacrifice grass in the short term in an effort to rid your lawn of Khaki weed seed over the long term. Spray in the coolest part of the day when chemical uptake is most likely by the plant.  When you spray, use a bucket or plastic wrap to protect plants adjacent to the weed.

Try to treat when the first Khaki weeds are no more than 3 to 4 leaves per plant.  In your lawn, you may see new weeds after every rain event, even if it was only 2 to 3 tenths and as late as September.  In large areas of solid Khaki weed, spray the entire area, leaving tufts of grass as possible.

Sorry to say, but there are no easy answers at this point.