A member of the Asteraceae family, the weed Bidens pilosa Linn. is found throughout the world, probably originating in South America. First noted in Linneus's Species Plantarum (1753) (1), this weed has acquired a variety of common names: cobblers pegs, grab-a-leg, Spanish needles, pitchforks, stickybeak, hairy tickweed and many more. When it was introduced to Australia is unknown, but it is now prevalent in the Northern Territory, South Australia, Queensland and New South Wales, and is a major crop weed, outcompeting native species in tropical areas (2). B. pilosa is an erect annual which grows to an average height of 60 cm although it can reach 2 m in favourable conditions. The leaves are opposite and divided into three to five lance-shaped segments with serrated edges. Bright green whilst young, leaves can develop tinges of red and brown on maturity. Flowers are mostly yellow but can have white elements (ray florets) which can be present for periods of the flower's development. The seeds are black or dark brown, slender and about 1cm long, clustered on the end of the stalk. They possess three tiny prongs at one end, which adhere to clothing and animals(2).