Chamberbitter

Prepared by Chuck Burgess, HGIC Information Specialist, Clemson University. Revised by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University. (New 09/05. 11/09.)

HGIC 2314

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Chamberbitter (Phyllanthus urinaria) is also known as gripeweed, leafflower or little mimosa. It is a warm-season, annual, broadleaf weed that emerges from warm soils beginning in early summer. It reproduces by seeds, which are found in the green, warty-like fruit attached to the underside of the branch.

Chamberbitter grows upright and has a well developed taproot. The leaves are arranged in two rows on the branchlets and are thin and oblong, with smooth margins, resembling a mimosa seedling.

Management of chamberbitter is best achieved through the integrated use of mechanical, cultural, and chemical methods.

Mechanical Control

Mechanical weed control involves the physical removal of the weed from the soil. This is best accomplished by hand when weeds are young and small, or in the seedling stage, and is made easier if the soil is moist. Preventing the weed from reaching maturity and setting seed also reduces future weed populations.

Cultural Control

Cultural weed control is the prevention of weeds through proper lawn management practices. A properly mowed turf that is not stressed by insects, diseases, drought, or nutrient imbalance is the best defense against weeds. For more information on watering, fertilizing and mowing see the following fact sheets: HGIC 1201, Fertilizing Lawns, HGIC 1205, Mowing Lawns and HGIC 1207, Watering Lawns.

In landscape beds, apply two to three inches of mulch in the spring to cover seeds from the previous season. Because chamberbitter seeds require light to germinate, this is especially effective.

Chemical Control

Control in Lawns:

Preemergence Herbicides: Because preemergence herbicides prevent seedlings from developing, they are an effective tool against annual weeds. However, they will not affect established weeds. Timing is critical. They must be applied prior to seed germination.

Atrazine (Hi-Yield Atrazine Weed Killer, Southern Ag Atrazine St. Augustine Weed Killer, Image for St. Augustinegrass & Centipedegrass with Atrazine, and Spectracide Weed Stop for Lawns Conc. for St. Augustine & Centipede Lawns) is effective for preemergence control of chamberbitter in centipedegrass and in St. Augustinegrass. Be careful not to apply on turf during the transition period from dormancy to active growth. Because chamberbitter tends to germinate in late spring and early summer, applications after grasses green up are effective. Target areas where chamberbitter was observed the previous season and be careful to not apply near the roots of desirable landscape plants. For more information refer to HGIC 2310, Managing Weeds in Warm Season Lawns

Postemergence Herbicides: Postemergence herbicides are most effective when applied to young weeds. For postemergence control of chamberbitter in St. Augustinegrass and centipedegrass, atrazine is recommended. It has both preemergence and postemergence properties. Make two applications spaced 30 days apart. In fescue, bermudagrass, and zoysiagrass repeat applications of three-way herbicides that contain 2,4-D, MCPP and dicamba (examples are Weed-B-Gon Weed Killer for Lawns and Trimec Southern) will be necessary to control chamberbitter. Apply these herbicides in late spring or early summer when the weeds are still young and space applications seven days apart.

Control in Landscape Beds

The best choice for controlling chamberbitter in landscape beds is one of the many products containing glyphosate. Examples include Roundup Weed and Grass Killer Super Concentrate, Eraser, Glypho, and Glyphomax. Glyphosate, the active ingredient in these products, will move through the plant and into the root to kill the entire plant.

Glyphosate is a non-selective herbicide which can potentially damage any plant through contact with foliage or bark. Protect desirable plants from drift by not spraying in windy conditions, by keeping the spray nozzle close to the ground, and by using low pressure. Further protection is provided by attaching a plastic, cone shaped shield that surrounds the spray nozzle and confines the spray to the targeted plants. Shields can be made from bottomless two liter drink bottles. Plants can also be shielded by covering with cardboard or something similar that is disposable.

Pesticide Safety

Always read the pesticide label and follow its directions exactly. Be sure to observe all precautions listed on the label. Mix pesticides at the rate recommended and never use more than the label says. Wear protective clothing or equipment as required by the label when mixing or applying pesticides. You may use the pesticide only on sites or crops listed on the label. Follow all label directions for pesticide storage and disposal. Always heed the six most important words on the label: "Keep out of reach of children."