Eliminate grass burrs from the lawn by applying pre-emergent herbicide two to four weeks before weeds are due to germinate, applying more pre-emergent herbicide every six weeks and treating any weeds that do germinate with post-emergent herbicide. More generally, keep the lawn healthy to prevent grass burrs.
- Apply pre-emergent herbicide
Ask your local extension agent when soil temperatures normally reach 52 degrees Fahrenheit in your area. Apply pre-emergent herbicide that the manufacturer formulates to kill grass burrs to the lawn at that time. Do not apply the herbicide too early, because it loses its effectiveness after four to six weeks.
- Reapply the pre-emergent herbicide
Apply more herbicide every six weeks during the growing season to prevent germination of other seeds that are lying dormant in the lawn. Grass burrs thrive in drought conditions and without treatment, seeds continue to germinate throughout the season.
- Use a post-emergent herbicide
Even with regular application of pre-emergent herbicide, some grass burrs are likely to germinate. Treat them as soon as they are recognizable using a post-emergent herbicide. Avoid waiting until the weeds are mature and have set seeds that are a nuisance in the lawn and propagate the plant again the next growing season. Do not use a post-emergent weed-and-feed, as this is less effective than a post-emergent herbicide that makes contact with the leaves of the plant.