 Noxious weeds are a large problem in many parts of the world, greatly affecting areas of agriculture, forest management, nature reserves, parks and other open space.Many noxious weeds have come to new regions and countries through contaminated shipments of feed and crop seeds or were intentionally introduced as ornamental plants for horticultural use.Some "noxious weeds", such as ragwort, produce copious amounts of nectar, valuable for the survival of bees and other pollinators, or other advantages like larval host foods and habitats.