Notes on Invasive Species

There are many advantages to living in a global economy, but there are also costs.  One of these costs is the accidental introduction of exotic species, of which about 1 in 10 go on to establish in their new habitats and become invasive. Such biological invasions now occur at an unprecedented rate and scale. It is estimated that in the United States alone, more than 4,500 foreign species have established themselves in the past century. These biological invasions result in severe, often irreversible impacts on agriculture, recreation, and natural resources as well as threatening biodiversity, habitat quality, and ecosystem function. Invasive species are the second greatest threat to native species (after habitat destruction) and have directly caused the decline of nearly 49% of endangered and threatened species in North America. The financial cost of invasive species to the United States in total economic damages and associated control costs is estimated at about $137 billion per year.

Like most Midwest states, Indiana was inundated with a number of invasive pests of regulatory concern in 2004. In addition to actual finds of invasive species, Indiana maintains a constant vigil for exotic species that threaten the Midwest region. Since this is an entomological newsletter, let’s first look at the invertebrate component of these invasions, which began right away in January 2004 with the discovery of longhorned beetles (Chlorophorus sp.) and tortricid moths (Cydia spp.) discovered in pine cones from India sold in potpourri mixes for the holidays. Although only larval (not adult) beetles were found, several adult moths were collected. Asian ambrosia beetles (AAB) were collected in nurseries in three southern counties in Indiana during 2004.  First detected in South Carolina in the 1970s, this scolytid bark beetle is a pest of numerous trees, notably (in Indiana anyway) honey locusts and orchard trees. The buprestid emerald ash borer (EAB) was the most problematic invasive insect in the entire Midwest region last year.  EAB was detected in two Indiana counties, LaGrange and Steuben, in 2004.  This was no surprise as Indiana borders both Michigan and Ohio, which are also battling this pest.  If EAB is uncontrolled, it could remove North American ash trees as a species from the continent. An estimated 40,000 ash trees in Indiana will be destroyed by the spring 2005 in an effort to halt the pest, which has already killed 8 million ash trees in the Detroit area. Surveys continued for the European woodwasp (Sirex noctilio) which was intercepted by warehouse workers in Bloomington, Indiana in 2002.  Fortunately, no positive specimens have been collected to date and a possible crisis was averted by the warehouse workers’ actions in reporting their find to the authorities.  Total trap catches of European gypsy moth were down 75% from 2003, from 23,000 to about 9,000. The Indiana Department of Natural Resources (IDNR) will treat 22 sites for gypsy moth based on these catches in 2005, down from 39 sites in 2004.  Surveys for Old World bollworm were initiated in Indiana in 2004.  Although this insect is not currently known in the United States, over 49% of the continental U.S. is considered suitable habitat for it.  Old World bollworm is a highly polyphagous pest of many economically significant crops and feeds on over 180 cultivated and wild species. No specimens were collected and surveys will continue in 2005. Another longhorned beetle (Callidiellum sp.) from Asia was found in wooden trellises in Wisconsin last year.  The Indiana Department of Natural Resources recovered 8 trellises from around Indiana and collected 2 larvae from the trellises.  A joint survey between the USDA APHIS PPQ and the Indiana CAPS program for solid wood packing pests was performed at 55 sites in Indiana in 2004, targeting 16 invasive bark and wood-boring beetles.  o targeted pests were collected during the survey, but the serendipitous discovery of banded elm bark beetles (BEBB) in Marion County, Indiana during the survey made the efforts worthwhile.  BEBB, a pest of elm trees, was first found in 2002 in Utah and Colorado but is now quite widespread. Trapping for BEBB and other invasive bark beetles will continue in 2005.  Five new counties in southern Indiana were added and placed under quarantine for pine shoot beetle (PSB). Currently, 60 of 92 Indiana counties are under quarantine for PSB, which arrived in the U.S. in 1992. In December of 2004, brown fir longhorned beetle (Callidiellum villosulum) was found in the real-wood (complete with bark) trunk of an artificial Christmas tree from China by a consumer in Michigan.  Prior to the discovery, the distributor sent shipments of these artificial trees to Illinois and Michigan. So far none have surfaced in Indiana but there is some concern because of the proximity of the shipments.

Of course, all invasive species aren’t insects; there are many pathogens of concern.  Indiana participates in the USDA’s national survey for the fungal disease karnal bunt, providing information to support the karnal bunt–free status of grain exports from the United States. The USDA regulates wheat infected with karnal bunt, restricts the wheat’s movement to retain export markets that consider it a pest of quarantine significance, and keeps the fungus from spreading. Fortunately, all samples taken in 2004 from Indiana were negative. A pest of national concern (it even appears on the USDA’s Agricultural Bioterrorism Act of 2002 Select Agents and Toxins list) is the bacterial pathogen Ralstonia solanacearum. It causes common wilt in geraniums and infects numerous solanaceous plants (e.g., tomatoes, and peppers) and is a major concern to the potato industry. The ralstonia survey resulted in no detection of this pathogen in Indiana, but, because of the seriousness of this pest, future surveys are planned. In the spring of 2004, potentially infected ornamental plants were shipped throughout much of the U.S. containing that fungal pathogen Phytophera ramorum which causes Sudden Oak Death. The plants came from a few nurseries on the West Coast (California and Oregon) that inadvertently shipped containerized rhododendron, camellia and other plants that might have been infected with P. ramorum. IDNR Nursery Inspectors recovered 70 camellias in Indiana that originated from the West Coast shipments. Twenty Indiana nurseries were then surveyed using national protocols (Elisa tests and PCR) and 600 nurseries were surveyed visually but so far no positive finds from this pathogen were found in Indiana.

Of course, Indiana is also susceptible to invasion by plants. Giant hogweed was found near Warsaw, Indiana (Steuben County) this year.  This invasive plant is a high priority for detection and control due both to its threat to human health. Giant hogweed causes a skin reaction known as photo-dermatitis which results in large painful blisters with eruptions on humans. The Indiana Department of Natural Resources also conducted a survey for kudzu, the infamous strangling vine of the South that has unfortunately made its way into Yankee territory. So far in Indiana 55 kudzu sites have been found in 24 counties, for a total of 55 acres. Kudzu grows well under a wide range of conditions and in most soil types. Besides threatening landscapes, kudzu acts as an alternate host for soybean rust.  Brazilian elodea was found during an IDNR plant survey of another invasive plant, the Eurasian water milfoil.  This aquatic invasive plant was found in Bloomington's Griffy Lake and was treated by the Bloomington Water Company. Elodea, which forms in dense mats, threatens biological diversity by crowding out native plants and animals. Yellow floating heart, a popular garden ornamental that is an aggressive grower with the capability to establish in natural areas, was found on 3 private properties in Indiana last year. Fish and wildlife habitat, recreation, and water quality is negatively impacted when the dense mats of yellow floating heart outcompete native and beneficial plant species. The concern is that it will get into major rivers such as Wabash River and Sugar Creek River.

Last, but not least, there are vertebrate invasives. The European wall lizard became the first invasive lizard found in Indiana and was detected at the Falls of the Ohio State Park. The lizard has the potential to reach high populations densities and to displace native species of lizards including the 5-lined skink.  Finally, the Indiana Department of Natural Resources issued a quarantine banning the sale of the Giant African land snail. Giant African land snails can carry the rat lung worm, which can cause individuals who eat raw or undercooked snails to develop meningitis and to suffer from permanent neurological damage. Approximately 200 Giant African Land Snails were collected and incinerated from owners in Muncie and Wabash, Indiana.

Although Indiana is seemingly landlocked, we certainly do not lack invasive species. Fighting them, although extremely costly and time-consuming, is well worth the effort to preserve our natural resources.

~ Christopher M F. Pierce ~