According to the New Zealand Biodiversity Strategy plant pests or weeds are one of the greatest threats to biodiversity in New Zealand. Many pretty exotic ferns, herbs, shrubs and trees planted originally as “ornamentals” have turned into ugly weeds. Most weeds have originated as garden escapes. They interfere with native plant regeneration, alter native plant communities, and destroy valuable habitat for native plants and animals. Weed control is costing taxpayers millions of dollars each year to prevent exotics from dominating entire ecosystems.