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 Canada – the gall wasp Aulacidea subterminalis in 2011 and the hoverfly Cheilosia urbana in 2017.
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.
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.
Attractive pink flowers make the Eurasian plant flowering rush a popular aquatic ornamental. But since it was introduced to North America it has become an aggressive invader of freshwater systems in the midwestern/ western USA and western Canada. One likely reason for this is the absence of the natural enemies that keep it in check in its area of origin. CABI is searching for natural enemies that could be introduced to reduce its vigour and spread in North America.
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.
Although closely related, Oxeye daisy is an invasive weed in places like North America and Australia, while Shasta daisy remains a garden favourite, especially in North America. CABI is investigating whether specialist natural enemies from oxeye daisy’s area of origin in Eurasia could be introduced in North America and Australia as biological control agents. In North America the popularity of Shasta daisy makes this a challenge because any introduced agent must damage oxeye daisy but not Shasta daisy.