Every summer I receive more phone calls about lawn burweed or sticker weed than any other lawn problem that we have. During the summer is when the stickers show up. The stickers are the seeds that the plant produces to get next year’s crop in the ground and ready to come up. The biggest problem with controlling lawn burweed is that once we notice the stickers, it is really too late to do anything about them. The plant has matured and is at the end of its life cycle, so it’s about to die anyway. The stickers will stay around for a bit, even on the dead plant.
Lawn burweed is considered a cool-season plant, and it begins its life late winter to early spring. That is the best time is to control them, which means now. To control lawn burweed, selective herbicides can be applied between January and March to kill these weeds when they are still small and actively growing. Using herbicides to kill young weeds will help reduce the amount of weed seed in the soil by preventing the plants from maturing and dropping new seeds into the soil for next year’s crop.
Herbicides available to homeowners that will control lawn burweed and not harm your grasses contain the active ingredient atrazine or a combination of the active ingredients 2,4,D, mecoprop and dicamba. Atrazine in commonly sold as Bonus S, Purge II and under other brand names. The combination is available under brand names including Weed-B-Gone and Lesco Three Way. Both of the products are safe when applied to warm-season grasses if label directions are followed. Care must be taken when using products containing 2,4,D on centipede and St. Augustine lawns. Reduced rates are typically recommended according to label directions. When buying any pesticide, always make sure you are getting the correct active ingredient by checking the product’s label. Always read and follow label directions when using any pesticide.
I’ll also go ahead and answer another question that I start getting in the early spring. When the phone starts ringing because the winter weeds are tall and green, I’m asked when is the best time to put out a weed and feed? The answer to that is there is never a best time to put out a weed and feed. The problem with a weed and feed is the optimum time to fertilize is not the optimum time to apply weed killers, and vice-versa. Our lawns should not be fertilized until they have greened up well and are actively growing. Fertilizing lawns too early can encourage large patch, a fungal disease that is very destructive to our lawns. So consider backing off of the so-called need to apply a weed and feed fertilize at the proper time and control weeds when they are in the part of their life cycle that is effective to control them.
The LSU AgCenter and the LSU College of Agriculture