Family: Pistia occidentalis Blume

Common names: Water Lettuce, Laitue D'Eau, Lechuguita de Agua, Repollo de Agua, Apon-apon, Apoe-apoe, Beo-cai, Chawk

A free floating, stoloniferous, monocotyledonous perennial with long feathery roots, bearing small plants (off shoots) at the end of each stolon. Leaves are pale green, overlapping, wedge shaped, succulent, up to 10 cm long and 5 cm wide, covered on both surfaces with numerous fine hairs, forming a rosette about 15 cm in diameter on a short stem axis. Older leaves have a conspicuous, ovoid swelling filled with spongy parenchyma on the lower surface. Prominent veins are arranged in a fan like manner.

The inflorescence is composed of inconspicuous flowers: small, green; surrounded by green tubular spathes arising in the leaf axis in the centre of the leaf whorl. Fruits are green berry like, slimy, rupturing irregularly, containing 4 12 brown seeds. Seeds are oblong, tapering towards the apex, 2 2.5 mm long, with a thick regulose seed coat.

It usually propagates by means of stolons which break easily from the plant accounts. Reproduction also takes place by seeds.

It is a common floating plant in dams, lagoons, lakes and also grows in wetland rice all over the hot climatic world. It is also found floating on stagnant water and sometimes rooting on muddy banks. Like water hyacinth this plant also blocks irrigation canals and provides a breeding ground for mosquitoes and choking fishery waters.

The Curculionid weevil Neohydronomous pulchellus, which was collected in South America substantially reduced growth of Pistia stratiotes in Australia and Zimbabwe. Recently, this control method has also been successfully implemented in Ivory Coast.

This is the most sustainable method to control this free- floating weed.

Countries: Côte d'Ivoire, Cuba, Dominican Republic, Ghana, Guyana, Mali, Nepal, Nicaragua, Panama, Senegal, Thailand,

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