Pacific Pests, Pathogens and Weeds

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Summary

• Widespread. Asia, Africa, North, South and Central America, Oceania. In Australia, Fiji, PNG.
• Invasive, long-lived, much-branching, creeping weed of plantations, orchards, vegetable fields, wet pastures, field borders, roadsides, gardens and wasteland. Mainly problem in open, moist habitats with disturbed soils, and young crops. Withstands temporary flooding.  
• Soft, smooth, fleshy stems, up to 100 cm long, enclosed by sheath at base. Leaves, 4-6 cm long, alternate along stems, with hairs on margins. Flowers, small clusters in upper leaf forks, three bright blue petals, opening in morning. Seeds, dark-brown. Roots from nodes along stems.
• Spread: vegetative propagation; seeds; stem pieces; water; soil; as a medicinal plant and ornamental.
• Biosecurity: moderately high risk of introduction; used as an ornamental. Available on internet.
• Biocontrol: Little known.
• Cultural control: hand weed or hoe (but stem pieces regrow); cultivation (mechanical or animal drawn); cover crops; increase crop density.
• Chemical control: in Australia: bentazone; glyphosate; fluroxypyr; pendimethalin. In Fiji, metsulfuron-methyl.