Chamberbitter, scientifically known as Phyllanthus urinaria, is a persistent summer annual weed that quickly colonizes thin turf. The difficulty is compounded when the weed invades centipede grass (Eremochloa ophiuroides), a warm-season turf type known for its sensitivity to many common broadleaf herbicides. Successfully eliminating chamberbitter requires a targeted approach that utilizes specific chemical strategies and precise timing to protect the centipede lawn. This article details the methods and products effective for managing this troublesome weed without causing damage to the surrounding turf.
Identifying Chamberbitter and Its Life Cycle
Chamberbitter is often mistaken for a small mimosa seedling because its compound-like leaves fold up at night. The plant features oblong leaves arranged in two rows along slender, upright stems. A distinguishing feature is the presence of small, round fruit capsules located directly on the underside of the branches at the leaf axils.
This weed is a warm-season annual that germinates from seed when soil temperatures warm consistently. Chamberbitter requires soil temperatures to reach approximately 70 to 75 degrees Fahrenheit before seeds sprout, typically in late spring or early summer. It develops a deep taproot, making hand-pulling difficult once the plant matures.
The plant’s prolific seed production and dispersal mechanism complicate control. Mature seed capsules undergo explosive dehiscence, scattering seeds rapidly. This ensures a continuous supply of future weeds throughout the growing season, necessitating a multi-pronged control strategy.
Safe Pre-Emergent Strategies for Centipede Grass
Effective control of chamberbitter begins with applying pre-emergent herbicides that stop seeds from germinating. A pre-emergent product works by forming a chemical barrier in the top layer of the soil, which prevents the weed seedling from establishing a root system. This barrier must be in place before the weed seeds begin to germinate.
Timing the application is crucial and should occur in late spring, after the centipede grass has fully greened up following winter dormancy. Since chamberbitter requires warm soil, the pre-emergent should be applied just before the soil consistently reaches 70 degrees Fahrenheit, often corresponding to late April or early May. Active ingredients proven safe for centipede grass and effective against chamberbitter include atrazine and isoxaben.
Isoxaben is a widely recommended pre-emergent for warm-season turfgrasses, offering effective control. Granular formulations must be watered into the turf immediately after application to establish the protective soil barrier. Prodiamine and pendimethalin are also safe for centipede grass and provide broad-spectrum pre-emergent control.
Post-Emergent Herbicides Safe for Centipede
When chamberbitter has already emerged, a post-emergent herbicide is necessary to kill the existing plants. Centipede grass is sensitive to many common broadleaf weed killers, particularly those containing high rates of 2,4-D, which can injure the turf. Selecting a chemical that is both effective against the weed and gentle on the grass is important.
The active ingredient atrazine is highly effective for post-emergent control in centipede grass. Atrazine functions as a selective herbicide, interfering with the weed’s ability to photosynthesize. It is effective when applied to young chamberbitter plants and is safe for use once the turf is actively growing and fully green.
Another effective option is a combination product containing thiencarbazone, iodosulfuron, and dicamba. This formulation is safe for centipede turf and provides excellent control over tough weeds like chamberbitter, especially when applied during warm weather. Mixtures of 2,4-D, mecoprop (MCPP), and dicamba (three-way herbicides) can be used, but they must be applied at the lowest recommended rate to avoid turf injury.
Optimal Timing and Application Techniques
The success of post-emergent treatment depends on proper timing and application methods. Herbicides are most effective when chamberbitter plants are small seedlings, before they develop seed-bearing fruit. Treating mature plants often requires higher rates or multiple treatments to achieve control.
Applications should only be made when the centipede grass is healthy, actively growing, and not under stress from drought or heat. Avoid spraying most herbicides when the air temperature exceeds 90 degrees Fahrenheit, as this increases the risk of turf damage. However, some newer chemical formulations, such as those containing thiencarbazone, iodosulfuron, and dicamba, are formulated for use in high-heat conditions.
Repeat applications are often necessary because seeds continue germinating throughout the summer. A second application, typically spaced three to four weeks after the first, helps control newly emerged weeds. Always use a spot-treatment approach where possible to minimize the amount of chemical applied, and strictly follow the manufacturer’s label instructions.