INVASIVE SPECIES
Charles G. Helm and Robert N. Wiedenmann
The natural, agricultural, and urban environments of Illinois have been and continue to be permanently altered by both accidental and intentional introductions of exotic, invasive species. These basically are species that are not native within the boundaries of the U.S. but have become "biologically established" to the detriment of local flora and fauna. Invasive species cost the Illinois economy millions of dollars annually in control measures and damage, and some of these species may also adversely affect human health, displace native species, or seriously degrade environmental quality. If a newly discovered exotic pest presents serious economic and environmental threats only within a limited geographical boundary, regulatory officials may first attempt to eradicate the unwanted invader. While the goal of eradication may be technically feasible, such efforts are often extremely costly, complicated, and may be subject to public opposition. In other instances, when an exotic species has become firmly established over a wide geographic range, comprehensive strategies for containment or management must be developed in order to maximize effectiveness against the targeted organism while minimizing negative impacts on native species and their habitats. INHS scientists represent a unique resource by providing basic biological research, pest management strategies, and outreach expertise to address the growing threats posed by exotic invaders.
Preventing new introductions of harmful species is clearly the first line of defense. Port inspection and quarantine are the responsibilities of the U. S. Department of Agriculture Division of Plant Protection and Quarantine and the Illinois Department of Agriculture. However, INHS scientists are closely linked to the activities of both of these agencies through the Cooperative Agricultural Pest Survey (CAPS) program, a cooperative survey network of state and federal agencies focused on the early detection of exotic pests not yet known to occur in the U.S. or the monitoring of newly established invasive species. Recent targets include an Asian maize borer in corn, a complex of European weevils in alfalfa, and the highly publicized Asian longhorned beetle in the Chicago metropolitan area. Surveys of the Asian longhorned beetle have been the primary responsibility of Illinois Department of Agriculture, U.S. Forest Service, and the USDA Animal and Plant Health Inspection Service. Nonetheless, INHS scientists prepared and distributed Insect Info fact sheets, provided updates to the Board of Natural Resources and the House Agricultural Committee, and monitored survey and tree removal activities aimed at eradication of this pest. Over 800 trees have been removed from infested areas in Ravenswood, Summit, and Addison, but intensive surveys and additional removal of infested trees could continue for several more years before this outbreak is fully contained. Several million dollars have already been expended on survey, removal, and replanting, but the aesthetic costs to affected neighborhoods are immeasurable. Lack of local quarantine facilities prevents detailed biological studies, but INHS scientists are mounting a program of public awareness and education to ensure the earliest possible detection of new infestations of this serious threat to our urban forests.
Zebra mussles on a brick.
Threats to human health are posed by the Asian tiger mosquito, which is capable of transmitting 26 viruses that cause disease in man as well as the parasite responsible for dog heartworm, a major problem in every Illinois county. Researchers are studying the biology and ecology of this mosquito to clarify its importance as a public health threat and its ecological effects on the distribution and dynamics of native mosquitoes and other aquatic macroinvertebrates. Long-term studies of the role of major waste-tire sites in the dispersal of this container-breeding mosquito will help determine if cleanups of these sites may help limit the spread of this significant nuisance pest.
Present in Illinois waters since the early 1970s, the exotic rusty crayfish continues to expand its range across the northern half of the state, displacing native Illinois crayfishes and extirpating several local populations of at least two native species. Building on a study conducted in 1995, INHS researchers are continuing to document the rusty crayfish's expansion in Illinois with the hope of determining which native species are most susceptible to displacement and which habitat types facilitate displacement by the invading species. Currently, there are no known means for eradicating exotic crayfishes, but it is hoped that data gathered by Survey scientists and researchers at other institutions may eventually be used to develop such methods.
A variety of invasive exotic species are having negative economic and environmental impacts on Lake Michigan and its connecting waters. In fact, there are so many introduced species in the Great Lakes that some biologists consider it a man-made aquaculture system. Scientists at INHS are conducting intensive research involving several of these
species to understand their long-term impacts and possible methods for their control. Two exotic
species, the zebra mussel and the spiny water flea,
have been linked to serious declines in yellow perch populations resulting in the imposition of significant restrictions on this once-thriving sport and commercial fishery. Coincident with the introduction of both of these invasive species has been a documented decline in zooplankton, an important food source essential to the survival of young yellow perch.
Research by INHS scientists has also shown that downstream dispersal of zebra mussel populations from Lake Michigan into the Illinois River helps maintain their populations under suboptimal conditions in the river. Current research is exploring the potential to control the mussel in the Illinois River by interrupting this downstream flow of larvae. If successful, this project could protect downstream ecosystems from the impacts of zebra mussels and save public utilities along the Illinois River millions of dollars currently spent on zebra mussel control.
Teachers head to
purple
loosestrife
research site during a field day workshop conducted by
INHS.
The Great Lakes have also been invaded by the round goby, an aggressive,
highly competitive exotic fish. Even as studies to determine the impact of
gobies on the entire spectrum of native fish communities within Lake Michigan
continue, researchers are already concentrating on the potential of the round
goby to spread into tributary streams and waterways connected to the Great
Lakes, particularly the Mississippi and Illinois River systems. Preliminary
studies suggest that the invasion potential and detrimental impact of the round
goby on species native to these watersheds is extremely high. Federal and state
authorities are considering the development of an electric fish barrier in the
Calumet-Saginaw Canal to help prevent the downstream spread of gobies into the
Illinois River.
Purple loosestrife is a perennial weed of European origin that has gradually come to dominate many of the remaining high-quality wetlands in the northern half of Illinois. Efforts to control vast stands of this weed using conventional methods, such as herbicides or hand removal, have been largely unsuccessful. However, an innovative biological control program developed by INHS personnel is showing promising signs of reducing populations of this highly competitive weed. This program emphasizes (1) mass-rearing and release of imported loosestrife-feeding beetles; (2) partnerships with IDNR, County Forest Preserves and Conservation Districts, the U.S Army Corps of Engineers, the U.S. Fish and Wildlife Service, and municipal park districts; (3) an educational component to increase public awareness; and (4) on-site rearing of beetles by nature centers, homeowner groups, schools, and land managers. Given the potential for control of purple loosestrife shown by this project, researchers are now exploring the possibility of a similar program to manage the growing problem of garlic mustard. This weed is rapidly invading the forests of northern and central Illinois and displacing native woodland wildflowers. Much like purple loosestrife, dense populations are proving difficult to manage with conventional controls, suggesting it may also be a candidate for biological control.
The risk of continued introductions of exotic invasive species remains high., and is of the utmost importance to the landscape, economy, and citizens of Illinois. This brief overview of a select group of research projects dealing with invasive species is an indication of the extensive effort that INHS scientists are expending to address this critical issue. Together with other governmental agencies and commercial and private interests, INHS researchers will continue to play a key role in advising how best to reduce introductions, eradicate new infestations, and manage those invasive species that become established.
INHS RESEARCH PROJECTS IN INVASIVE SPECIES AND BIOLOGICAL CONTROL
*Biological control of lepidopteran stalkborers
R. Wiedenmann, C. Helm, M. Alleyne, F. Cardona, R. Escolan, D. Roman
*Biological control of purple loosestrife
R. Wiedenmann, S. Post, C. Helm, R. Velarde, A. Wegeng, F. Cardona, R. Escolan,
D. Roman
*Biological control in home gardens and landscapes
R. Wiedenmann, A. Wegeng, D. Roman
*Biological control of alfalfa blotch leafminer
R. Wiedenmann
*Biological control of purple loosestrife
R. Wiedenmann, D. Voegtlin
*Carp, culture, and a century of exotic species introductions: an
environmental
history
D.W. Schneider, G. Sandiford
*Population and energetic consequences of zebra mussel fouling on native
gastropod fauna of Lake Michigan
D.W. Schneider, J.E. Marsden, D.K. Padilla
*Model plan to restrict the spread of aquatic nuisance species via
baitfish and
fish for stocking
P.M. Charlebois
*Trophic transfer of PCBs: zebra mussels and round gobies
P.M. Charlebois
*Abundance and size distribution of zebra mussel veligers in the
Mississippi
River
J.A. Stoeckel, T.M. Koel
*Model of Lake Michigan-Illinois River zebra mussel metapopulation:
evaluating possible control strategies
D.W. Schneider, R.E. Sparks, K.D. Blodgett, J.A. Stoeckel
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