In the summer of 2003, I was a hired gun for the Illinois Exotic Species Task Force. My primary mission was simple: eradicate populations of kudzu (Pueraria lobata). This invasive exotic plant was responsible for consuming millions of acres of forestland across the Deep South in a veil of jungle-like vines.
My mission took me across the state of Illinois and up against urban infestations in Peoria to “Kudzu Mountain” in the Shawnee Hills. My job was to protect our natural resources from exotic plants and animals. When I came to Missouri, I brought my work with me.
Know your enemy
Exotic (or “nonnative”) species are those that didn’t exist here before European settlement within the state’s present boundaries. An invasive exotic species is one that is likely to cause harm to the economy, the environment or to human health.
There are many exotics within the state, but only a rebellious few cause problems within Missouri’s ecosystems. Roughly 28 percent of Missouri’s flora is made up of exotic plants introduced to the state, while only 4 percent are considered invasive.
The invasive exotics are ranked (from high to low priority) as highly invasive, moderately invasive, widespread, or locally invasive. Highly invasive species are of most concern because they reproduce prolifically and compete aggressively. They can replace or exclude native species because they are not held in check by the natural pressures of predation, disease or competition that kept them in check in their native habitats.
Invasive species include a variety of exotic plants, insects, fish, mollusks, crustaceans, mammals, birds, reptiles, amphibians and pathogens. They threaten what we as Missourians hold dear—our fisheries, forests, wetlands, prairies and wildlife. Invasives account for damages and losses totaling approximately $137 billion each year in the U.S. They damage our ecosystems, push out native organisms, and alter our landscapes. Approximately 400 of the 958 species recognized as threatened or endangered by the Endangered Species Act are declining due to competition with invasive species.
By land, sea and air
Invasive exotics are transported from ecosystem to ecosystem both intentionally and unintentionally. Purchasing an invasive plant such as a burning bush, purple loosestrife or a bush honeysuckle and transplanting it into your yard is an example of an intentional introduction. So is knowingly transporting invasive seeds, whole plants or cuttings, live animals or pathogens with the intent to establish, maintain or release them into a new area.
Invasives are introduced unintentionally when gypsy moth egg masses are transported on your motor home; zebra mussel larva ride along in the bilge of your bass boat; or garlic mustard seeds cling to your favorite hiking boots. Intentional or unintentional, movements of exotic pests lead to an overall reduction in biodiversity—a simplification of the variety in our natural world.
Kudzu was introduced from Japan and China in the 1900s. It was widely promoted, particularly in southern states, for erosion control. The “Mile-a-Minute Vine” or “The Vine That Ate the South” was even planted as an ornamental plant. The USDA recognized kudzu as a weed species in 1972 and as a noxious weed in Missouri in 2004. It is estimated that kudzu populations cover some 7 million acres across the United States.
Recently, I was sent to eradicate a kudzu population in Missouri that had been planted years ago. It had a foothold and would be difficult to dislodge. The landowner told me his mother had planted it during the depression years. She had ordered it from a catalog where it had been advertised as a “porch vine fromthe orient.” A porch vine indeed—it shrouded the abandoned farmstead and a few acres of timbered land; the crumpled trees stood strangled in the distance.
The good fight and the bad seed
Protocols for managing invasive species have been developed in recent years to protect native ecosystems. Many of these plans read like orders for military operations and use phrases in their titles like “National Strategy and Implementation Plan” or “National Early Warning and Rapid Response.” All aim to stop invasives before they get here. If they’ve already arrived, the goal is to eliminate them before they become established. And in the worst-case scenario, with established invasives, the focus becomes defending the most pristine natural settings, the true jewels.
Managing the invasion of countless exotic species requires coordination and collaboration from nationwide to local levels. Education and prevention are the first steps. Missourians need to be aware that the choices they make determine the future health of our natural resources. This means carefully considering which plants to use in landscaping, as well as inspecting and cleaning equipment that has traveled with you. These may seem like small steps, but introductions of invasives are usually relatively simple events.
Eradication is the next step, and if conducted early, disasters can sometimes be abated. This is where early detection and rapid response comes into play. This protocol is usually reserved for agricultural pests and threats to human health, but it has been used to defend natural communities as well. Eradication requires quick action and aggressive tactics. Examples include incinerating trees harboring Asian long-horned beetles or trapping feral hogs.
Once an invasive species becomes established, control methods may include chemical, cultural, mechanical or even biological control measures. Chemical control includes the careful application of pesticides or herbicides. Cultural control means sound land stewardship such as planting native cover types, controlling grazing pressures on rangeland or minimizing disturbances that allow an invasive to get established. Mechanical control may involve the use of machinery, flooding or prescription fire. Lastly, biological control refers to the introduction of another species to help control the invasive one. Often, these species are natural enemies of the pest and may feed upon, parasitize or interrupt the life cycle of the target species. Using a combination of these methods is called integrated pest management and can boost effectiveness.
The kudzu population I had been sent to kill didn’t cover that much acreage, but (like all kudzu populations) it had visions of grandeur. I snapped images on my digital camera to document the pretreatment condition of the site and donned my nitrile gloves. Two hundred gallons of mixed herbicide continued to slosh within the baffles of my spray tank from the agitation of miles of travel, causing my truck to wobble as I shut it down. I surveyed my mission’s objective.
I snaked a high-pressure hose through the tangled mat of vines and broken treetops. Then I touched off the ignition on my pumper, and it roared to life. I made the typical adjustments to pressure up the system, pressed my goggles down against my face and pulled my drift hat down as far as I could. Picking up the nozzle, I lined up the first vine-canopied tree and squeezed the hand-trigger. The nozzle bucked and the solution sizzled skyward to meet tendril and leaf
Learn more about invasive species:
- MDC Online: www.MissouriConservation.org/nathis/exotic
- The Invasive Species Initiative, The Nature Conservancy: tncweeds.ucdavis.edu
- National Invasive Species Council: www.invasivespecies.gov
- The Center for Plant Conservation: www.centerforplantconservation.org/invasives
- PCA Alien Plant Working Group: www.nps.gov/plants/alien/factmain.htm
- USDA Forest Service, USDA APHIS, and other contributors: www.invasive.org
- Missouri Botanical Garden: www.mobot.org
- Protect Your Waters: www.protectyourwaters.net
Reed canary grass & Purple loosestrife threaten wetland resources and diminish their capacity to sustain waterfowl populations.
Feral hogs threaten our deer and turkey populations, as well as the livestock that many of us rely on.
Sericea lespedeza invade prairies and rangelands, effectively reducing populations of bobwhite quail and greater prairie chickens.
West Nile virus threatens several species of Missouri birds, not to mention posing health problems for horses and people.
Kudzu has been identified as a host for Australasian soybean rust, a threat to the soybean farmer’s bottom line.
Northern snakehead fish, Asian carp & zebra mussels all have sights on our fisheries and native mussels.
Emerald ash borer & gypsy moth threaten our forest resources.
Chinese yam threatens the flora of our pristine streams with populations in the watersheds of the Current River.
Nonnative shrubs, such as bush honeysuckles, Chinese privet and winged burning bush dominate the understory of suburban wooded areas, effectively excluding native herbaceous species and disrupting oak regeneration.