Biological control of hawkweeds
European hawkweeds are invasive in North American pastures, where mechanical methods of control are difficult and ineffective. Chemical control with broad-spectrum herbicides is not selective and relatively expensive, with the weed often recolonising untreated pastures. Insects that feed on hawkweeds in Europe have been studied as potential biological control agents for North America since 2000. Two agents have been released in North America – the gall wasp, Aulacidea subterminalis, and the hoverfly, Cheilosia urban.
Revisiting biological control of field bindweed
Field bindweed is a Eurasian vine whose dense creeping and twining growth smothers other vegetation and its long-lived seeds and deep roots make it hard to control. It is a noxious weed of agricultural fields in temperate regions and has become invasive in North America. CABI is studying sustainable control methods using host-specific natural enemies, which could be introduced into North America as biological control agents.
Biological control of garlic mustard
Crushed garlic mustard leaves and seeds smell like cultivated garlic and have been used as flavouring in cooking for centuries. Garlic mustard is a brassica from Eurasia that was accidentally taken to North America and became invasive in many of its forests. Together with partners, CABI is exploring the possibility of using specially selected and tested insects from the native range in order to safely control the plants spread and impact in the introduced range.
Biological control of perennial pepperweed in the United States
Weeds like perennial pepperweed that have creeping root systems and prolific seed production are among the most difficult to control. This Eurasian mustard plant was accidentally introduced into North America with crop seed. One reason why it has become an invasive weed could be the absence of natural enemies that attack it in its area of origin. CABI is seeking to identify specialist natural enemies from Eurasia that can be introduced into North America as biological control agents.
Hope for biological control of houndstongue in the USA?
An invasive weed with close relatives among native species is a challenge for biological control. Houndstongue was introduced accidentally to North America from Eurasia in the mid-19th century. It has since invaded most Canadian provinces and adjacent US states. There are many native plants in the USA in the same family as houndstongue. CABI staff in Switzerland are investigating specialized natural enemies in the area of origin of the weed that could be introduced as biological control agents.
Controlling hoary cress in North America
Trade in seed brought crops to new regions, but many weeds were spread by this route too. Whitetops, also known as hoary cresses, arrived in the USA as contaminants of seed from Eurasia. They are now aggressive invaders of crops, rangeland and riverbanks. One reason for this is the absence of the natural enemies that keep them in check in their area of origin. CABI staff in Switzerland are looking into the prospects for biological control of these invasive plants.