Lee Rouse | 10/23/2017 3:03:59 PM
Virginia buttonweed (Diodia virginiana) is one of the worst summer weeds infesting Louisiana turfgrass. The spread of this weed has increased tremendously over the past few years. Due to the summer flooding last year and our mild winter, the weed is expected to be even worse this summer and fall. Buttonweed thrives in moist to wet soils and is highly drought tolerant as well. The weed has a prostrate growing habit and forms dense mats that smother out the lawn.
It is easily identified by its opposite-leaf arrangement and white flowers with four star-shaped petals, which sometimes can have pink streaks through the center of two of the sepals. Buttonweed gets its name from the seed capsules, which resemble buttons that hang on the underside of the stems. Every seed capsule contains two seeds and has close to a 100 percent germination rate. It can reproduce by seeds, roots, and stem fragments. The combination of these characteristics aids this weed in becoming the No. 1 weed problem in Southern turfgrass.
Unfortunately, you can’t mow Virginia buttonweed out of the lawn. The weed will set flowers, drop seed, and reproduce no matter how short you mow the lawn. Continue to mow the lawn at the appropriate height for your lawn species.
If you had Virginia buttonweed last year in your lawn, you can expect to see the mother plant re-emerging from the soil in late winter, and the seeds of the mother plant germinating this month and throughout the summer. It takes a herbicide-based program approach with herbicide applications starting when the mother plant emerges in late winter and includes periodic applications throughout the summer.
A herbicide-based control program for Virginia buttonweed includes Weed Free Zone (“trimec” type herbidides) applied in late winter and early spring when temperatures are under 90 degrees . Celsius herbicide and metsulfuron herbicides (MSM, Top Shot, or Mansion) are the go-to herbicides for summer applications on the weed. Repeated applications of these herbicides suppressed buttonweed in LSU AgCenter research trials. Celsius and metsulfuron are safe for all Southern turf except bahiagrass. Celsius can also damage carpetgrass. The metsulfuron product Top Shot may be more widely available at your local nurseries and garden centers. Severe buttonweed populations may have to be sprayed about every 30 to 45 days during summer with Celsius or metsulfuron, so stay vigilant! Expect some lawn yellowing with these herbicides. Always be sure to read and follow labeled directions of all pesticides.