NSP - Mimosa pigra




Family: Mimosaceae

Common names: Amourette, violet, Amourette riviére, Weyler

A leguminous shrub, up to 6 m tall, found in moist, open sites in the tropics. The stems are armed with broad-based prickles up to 7 mm long. The leaves are bipinnate, alternate and sensitive to touch. Flowers small and pink. Pods crowded, flat and straight. M. pigra propagates by seeds. The plant produces thousand of seeds linear-oblong.

M. pigra originated in tropical America and is now widespread throughout the tropics, having emerged during the 1970s as a serious weed of tropical wetlands. It is already affecting agriculture and conservation in Australia and Thailand and seems likely to increase further as a problem in the S.E. Asian region. In Australia, it is restricted to the coastal regions of the Northern Territory, while in Thailand, it is concentrated around Chiang Mai in the north, but with infestations in the Bangkok region also M. pigra is common in moist places and along the shores of rivers, and easily found in sugar cane, pastures, rice and root crops.  

Because there is little grassy understorey in thickets of M. pigra, it is difficult to destroy infestations with fire without applying fuel such as gelled gasoline from aircraft. Follow-up control must then be carried out, because, although seeds on the soil surface are destroyed, germination of seeds from the seed bank, within 5 cm of the soil surface, is enhanced.

Six natural enemies have been released in Australia following rigorous host-specificity testing, but have not yet had any discernible effect. Four of these have also been released in Thailand. The six include two seed-feeding bruchid beetles, one stem-feeding chrysomelid beetle, two stem-boring moths, and in January 1992, a flower-feeding weevil.

Some herbicides may eventually be used against the weed, such as fluroxypyr, hexazinone and tebuthiuron.


Countries: Cuba, Mali, Thailand


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