At our April meeting at Calvin College Ecosystem Preserve we learned about the latest research on insects and other biological agents controlling the spread of invasives. Dr. Doug Landis, Professor of Entomology at Michigan State University spoke about three dreaded invasive plants— purple loosestrife, spotted knapweed, and garlic mustard.
- All organisms have natural enemies that limit their abundance.
- In their native region many plants are effectively controlled by natural enemies.
- If biocontrol agents do not control the target weed both can remain abundant.
- If not host specific, agents may attack non-targeted plants.
In the U.S. the process below is regulated by the USDA.
- Selecting appropriate target weeds
- Selecting natural enemies
- Host specificity testing
- Release and evaluation efficiency
Examples in Michigan:
Purple Loosestrife – Galerucella calmariensis, commonly known as the black-margined loosestrife beetle, is a species of leaf beetle that eats off the growing points. It is a very successful agent in 3–5 years. The number of native plants have increased where loosestrife is suppressed.
Spotted Knapweed – Cyphocleonus achates is a weevil that attacks the plants roots. C. achates was released to the Hiawatha National Forest in Michigan’s Upper Peninsula in summer 2009.
Garlic Mustard – A search for suitable biological control agents for Garlic Mustard was started in 1998. Weevils in the genus Ceutorhynchus (Coleoptera: Curculionidae) are under consideration. C. allianrae and C. robertii weaken the plant. C. scrobicollis invades the roots and is the most effective. The USDA has tagged a proposal to introduce a biological control of Garlic Mustard, so hopefully this highly invasive plant will meet its demise in the U.S. in the near future.
The University of Rhode Island Biological Control http://web.uri.edu/biocontrol