Daniel Gill | 3/19/2015 6:48:47 PM
Virginia buttonweed (Diodia virginiana) is one of the leading weeds of Southern lawns. It is a warm season perennial weed that begins growing in spring and grows through the summer. The thick matting growth habit can crowd out lawns where it grows. Virginia buttonweed is not readily controlled by most lawn weed killers. It is one of the most difficult to control broadleaf weeds in lawns. Multiple herbicide applications over 2 summers are generally needed for heavy infestations.
Lawn weed killers that contain 2,4-D, mecoprop, dicamba and carfentrazone, such Weed B Gone Max for Southern Lawns, Weed Free Zone and Speed Zone, are effective in suppressing and somewhat effective in killing buttonweed with multiple applications. They are the best options among the herbicides commonly available to home gardeners at local nurseries.
Best control starts in the spring with an application of one of these products over the entire lawn in early April and again in early May. But, you should expect to make repeated herbicide applications through the summer after the April and May treatments. In LSU AgCenter research, it often takes 4 applications of herbicide to keep this weed in check and under control.
During summer, St. Augustine grass and centipede grass may be injured by these herbicides when applied in hot (>90 degrees) and humid weather. So, during the summer spot treat by just spraying patches of buttonweed. Minimize spraying the lawn grass as much as possible.
Repeated applications of the professional herbicides Celsius (thiencarbazone + iodosulfuron + dicamba) or metsulfuron (MSM Turf, Manor, Mansion) have performed best at suppressing and controlling Virginia buttonweed in LSU AgCenter trials. Celsius and metsulfuron are safe for all southern turf except bahiagrass. These herbicides are not restricted and can be applied by home gardeners. However, you will not likely find them at your local nurseries. But, you can order them online or check with local retail outlets that sell professional grade herbicides.
Persistent and regular spot treating with glyphosate over time is another way to help deal with this weed. Glyphosate (Roundup, Killzall and other brands) does a good job of killing this weed, but it kills the lawn grass as well – which is an issue. Be very careful to just spray the weeds when using this nonselective herbicide.