Invasive plants can cause economic and environmental damage. Nonindigenous plants cost an estimated 34 billion dollars annually in losses, damages, and control costs (Pimentel et al., 2000). In agricultural and natural areas, they can displace desirable vegetation, resulting in reduced productivity, wildlife forage, and habitat.
Many invasive plants have the uncanny ability to migrate along transportation corridors such as roadways and then move into fields and natural areas where they proliferate with alarming speed. As new roads are constructed and existing roads are expanded, the disturbance created with vegetation removal and soil movement can render areas vulnerable to invasive plants. Mowing of roadsides, usually done for safety purposes, can also spread seeds. Additionally, seeds can be moved on vehicles. All of these situations together create ample opportunities for invasive plants to spread. As we travel along roadways, we see these invasive plants and may wonder how they are dealt with. Agencies such as the Minnesota Department of Transportation (Mn/DOT) utilize a variety of tools to manage weeds.
Biological control is one tool that targets specific weed species such as leafy spurge, spotted knapweed and purple loosestrife. Classical biological control is the practice of reuniting a pest with its natural controls. This control method is sustainable, long lasting, and cost effective. For example, in its native range leafy spurge is kept in check by naturally occurring insects and diseases. When leafy spurge was accidentally introduced to North America , it proliferated uncontrollably without diseases and insects to hold infestation levels down. To bring leafy spurge into balance, Aphthona species of flea beetles are released at large leafy spurge infestations. Since the beetles are native to Eurasia , they underwent rigorous testing to ensure that they are host specific so will not feed on native or other desirable vegetation. The beetle larvae feed on leafy spurge roots and will weaken or kill the plants when a large beetle population is present. Since it takes many years for the beetle population to build to a damaging level, biological control is a long-term approach that takes patience.
Mn/DOT and many counties manage weeds such as leafy spurge and spotted knapweed with biological control. Many infestations have been successfully controlled to date. See the map above for new (2004-2007) leafy spurge biocontrol releases in the metro area and watch the infestations decrease over the coming years.
Weed biological control is a cooperative program in Minnesota . This means that agencies, organizations, businesses, and individuals can partner to share biological control insects. When bioagent populations are sufficiently large at a site, they are collected and distributed to new sites. The Minnesota Department of Agriculture (MDA) coordinates programs for leafy spurge and spotted knapweed biocontrol and the Minnesota Department of Natural Resources (DNR) coordinates the purple loosestrife program. Much of the work is done at the local level by County Agricultural Inspectors, Mn/DOT, and other cooperators.
Individuals can help control invasive plants by notifying their County Agricultural Inspector (CAI) of infestations. The CAI can then work with the appropriate land manager to implement control methods. If individuals are concerned that they have leafy spurge, spotted knapweed, or purple loosestrife on their land and would like to try biological control, they can work with their CAI to receive bioagents. A listing of CAIs can be found at
www.mda.state.mn.us/plants/weedcontrol/cailist.htm
Future projects include researching garlic mustard and buckthorn biocontrol (coordinated by the DNR) and common tansy biocontrol (coordinated by the MDA). Bioagents for these plants are being tested at this time and are not available yet.Yard and Garden News
