(News article for April 24, 2020)
When I was younger, we had a golden retriever that liked to graze on Virginia buttonweed. Eating of weeds by dogs is not an often-cited example of biological control, but my dad welcomed the help.
Not everyone has a weed-eating golden retriever, and unfortunately, this alone is not enough to adequately manage Virginia buttonweed, which is one of the top lawn weed issues in Louisiana.
One of the things that contributes to Virginia buttonweed being such a problem is the fact that is grows, flowers, and produces seed close to the ground. Also, the weed can root from broken stem pieces as well as spreading by seed. So, while mowing regularly and at the recommended height for a given turfgrass is enough to prevent a lot of weeds from producing seed [and thus from spreading], this doesn’t cut it for Virginia buttonweed.
Even though mowing at the appropriate height isn’t enough to control Virginia buttonweed, it’s worth repeating that good cultural practices – including maintaining soil pH in the optimum range, fertilizing at recommended times and rates, and mowing at an appropriate height for the turfgrass that you have –the foundation of good lawn weed management.
If you have Virginia buttonweed, though, some additional steps will be needed to get rid of it.
During April and May, as this weed is coming out of dormancy and new seedlings are growing from seed, herbicides containing 2,4-D, dicamba, and mecoprop (or these three ingredients along with carfentrazone) can be used to spot-treat it in most warm-season turfgrasses, including centipedegrass, St. Augustinegrass, bermudagrass, and zoysiagrass. Examples of products that contain these ingredients include Bioadvanced Southern Weed Killer for Lawns, Fertilome Weed Free Zone, Fertilome Weed-Out Lawn Weed Killer, Ortho Weed B Gon, and SpeedZone Southern.
It’s important to start spraying for Virginia buttonweed during the spring, since this is when the weed is more tender and susceptible to herbicides. However, herbicide applications will likely need to be continued into the summer to successfully manage it.
Herbicides with 2,4-D can injure some turfgrasses during hot weather. Once temperatures reach 85 °F, you can switch to either metsulfuron (e.g., MSM Turf or Manor) or the combination of thiencarbazone, iodosulfuron, and dicamba (Celsius). If the lawn has a heavy buttonweed population, it may be necessary to apply one of these products every four to six weeks.
When using any herbicide, be sure to ready and follow label directions.
During the fall, after Virginia buttonweed has flowered and begun to produce seed, hand-removal is probably the most effective management option. Place the plants in a bag so that seed is contained and not allowed to fall back into the lawn.
More information about lawn care can be found on the turfgrass section of our website.
If you have questions, please let me know.
Contact Mary Helen Ferguson.
Virginia buttonweed has white flowers with four petals. (Photo by Ron Strahan)