Derris elliptica (Wall.) Benth. (Fabaceae)

Derris is a small genus of vines that is found in the Old World tropics, especially South East Asia. The small, pink flower clusters of Derris elliptica, with the distinctive shape characteristic of peas and beans, are followed by leathery seedpods. However, flowers and fruits are rare in cultivation.

The genus is best known as a source of rotenone, a colourless, odourless compound that is extremely toxic to fish and invertebrates. However, rotenone is not unique to Derris. Rotenone's toxicity means Derris species are used as both piscicides and insecticides.

As an aid to fishing and fish farming, derris roots are pounded to release rotenone, and then thrown into the water. Dead or stunned fish float to the surface where they can be easily gathered up. In farming, the same method is used to clear ponds of existing predatory fish before introducing cultivated species. The small quantities of rotenone that persist in the edible parts of the fish are degraded by cooking.

In Europe and America, powdered derris root was widely used as an insecticide by both amateur and professional growers from the nineteenth century. The non-selectivity of rotenone makes it effective against many garden and horticultural pests, including greenfly, sawfly, caterpillars, thrips, small beetles and spider mite.