Invasive, exotic species that pose a threat to native plants and animals are making big news these days. It’s a global battle, and three high-profile examples include the Burmese Python in the Florida Everglades, the European Rabbit in Australia’s fertile coastal areas and the Nile Perch in Africa’s Lake Victoria.
Kentucky has its share of unwanted exotics that out-compete native species for food and living space, alter the landscape, cause environmental or economic harm, and pose a direct health threat to livestock, wildlife or humans.
Some are highly visible and seemingly innocuous like the European Starling, yet this nuisance bird can spread the histoplasmosis fungus to humans. Histoplasmosis is a disease affecting the lungs that can be fatal if left untreated.
Others exotics are so beautiful that no one believes they could be harmful. The best example might be purple loosestrife, whose brilliant blooms light up the late summer landscape, but the plant grows in such dense stands it crowds out native vegetation in wetlands.
Invasive plant species of concern in Kentucky include: bush honeysuckle, tall fescue, multiflora rose, kudzu, autumn-olive, garlic mustard and about 10 exotic species that impact wetlands.
Exotic animal species of concern include: alewife, emerald ash borer, zebra mussel, wild pig and Asian carp.
Here are some details on four of the most damaging exotics in Kentucky:
Asian Bush Honeysuckle
Asian Bush Honeysuckle is most often encountered in Kentucky growing along roadways. This tall, woody plant produces red berries, high in carbohydrates. Fruits are consumed readily by birds upon ripening during summer.
Passing through the bird’s digestive system frees the seed from the fruit, scarifies the seed coat, and provides a growth medium, since bird feces is high in mineral nutrients. Bush honeysuckle plants are usually found growing as understory, in dense stands.
Seedlings establish in areas of sparse herbaceous vegetation and can tolerate moderate shade. Bush Honeysuckle produces allelopathic chemicals that inhibit the growth of native plants. Shading is also an issue, as the plant leafs out before many native species and hold its foliage until November.
Bush honeysuckle impacts wildlife by shading out everything in the understory, creating a plant monoculture. It’s not unusual for stands to be several acres in size.
A forestry cutter is needed for big jobs. It grinds up the whole plant into a pile of mulch. Later, the area is sprayed with herbicide, to prevent stump sprouting. Another mechanical option in scattered plants or small stands is to wrap a chain around the plant’s base and pull it out of the ground by the roots with a tractor.
Emerald Ash Borer
It is hard to believe that a 1/2 inch-long dark metallic green beetle could someday be responsible for the loss of millions of ash trees in Kentucky.
The Emerald Ash Borer (EAB) ), Agrilus planipennis, a native to eastern Russia, northern China, Japan and Korea was first documented in the state in 2009. According to the University of Kentucky College of Agriculture, EAB has been found in over 40 Kentucky counties with high infestation rates in 10 Central Kentucky counties. Another 10 counties in the region have experienced significant increases in the past year.
The Kentucky Division of Forestry estimates that Kentucky has about 130.9 million white ash trees and 92.5 million green ash trees, based on the 2006 US Forest Service Inventory and Analysis.
Adult beetles emerge in the spring, in May to early June, and feed on ash leaves but cause little damage. After mating occurs, females lay 60 to 90 eggs on a nearby ash tree. It’s the larvae, the immature stage of the beetle, that does the damage, feeding on the inner bark (phloem), disrupting the tree’s ability to transport sugars and other nutrients. If enough of the flow is cut, or it happens fast enough, the tree will stress and eventually die.
Small game biologist Ben Robinson, of the Kentucky Department of Fish and Wildlife Resources, said it would be a big loss to wildlife if Kentucky’s ash trees disappeared.
“Ash trees are valuable as a seed source,” said Robinson, for songbirds, wild turkeys, even wood ducks in bottomland hardwood forests.”
The exotic, invasive beetle, probably arrived in North America in wood shipping crates carried by cargo ships originating in Asia. EAB was discovered in Canada in the late 1990s and southeastern Michigan in the summer of 2002. By 2012, EAB had spread to 17 other US states.
Ash trees are sacred to Native Americans, with many medicinal uses. In a mature forest, ash grown straight and reach enormous heights. They have compound leaves, paddle-shaped seeds and distinctive dark brown bark with diamond-shaped ridges.
Ash wood has a high strength-to-weight ratio and low shrinkage when dried. It is a valuable wood with many commercial uses for everything from flooring and electric guitar bodies, to tool handles, baseball bats and canoe seats, thwarts and yokes. Wood turners seek out large chunks of ash to make artisan salad bowls since the wood has no significant odor or taste.
There are several signs that an ash tree has become infested. Most obvious is the loss of the tree’s bark as woodpeckers try to get at the larvae. Branches in the tree’s canopy die, and sometimes suckers grow from the tree’s trunk.
Wild Pigs / Feral Hogs
Wild pigs are uninvited pests that compete with native game species for food and living space. They are incredibly destructive and pose a direct threat to rare and endangered species on sensitive areas such as nature preserves. They have huge appetites. Their incessant rooting can damage topsoil, and affect the regeneration of many important trees and plants.
Wild pigs have been found in at least 30 U.S. states and the Associated Press reported in 2013 that wild pigs were responsible for more than $1.5 billion in damage. Farmers, who depend on the land for their livelihood, are hard hit by wild pigs feeding on their clover, alfalfa, corn and other grains, while trampling fields.
Nearly half of the estimated number of wild pigs in the U.S. are found in southern states, including Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi and Texas. Wild pigs (Sus scrofa) are not native to this country. They were imported from Europe, first by Spanish explorers in the 1500s (for food), then in the 1900s by people who wanted to hunt them for sport.
While they arose from a variety of genetic origins, all are exotic species that pose serious ecological, economic and disease threats.
Wild pigs are mobile reservoirs for a host of parasitic, viral and bacterial infections. Some of these, such as swine brucellosis, are transmissible to humans. The wild pigs in Kentucky are a result of illegal releases. It is illegal to possess, sell or transport wild pigs in Kentucky.
In Kentucky, adults may weigh 150 to 200 pounds, but since they free-range for food, they tend to be leaner than domestic hogs. Coloration is typically dark, with coarse black and brown hair.
Wild pig eradication efforts in Kentucky are making progress. In 2010 it was determined that the number of counties with wild pigs had doubled since 2008, from 16 to 32.
“Now we have wild pigs in about 17 Kentucky counties,” said Chad Soard, a wildlife biologist with the Kentucky Department of Fish and Wildlife Resources, who coordinates the department’s wild pig eradication efforts. “No where do we have significant densities of wild pigs. It’s a needle in the haystack situation with most areas only having a handful of sounders (family groups).”
Control efforts are difficult and costly. Trapping and aerial gunning from helicopters have been proven to be the most effective ways to eradicate wild pigs. Wild pigs are typically captured in corral-type traps that allow the removal of entire family groups.
Kentucky’s wild pigs live primarily in forested terrain. “I suspect they are food stressed during cold winters like we are having this year,” said Soard. “Wild pigs need high quality (high calorie) food. They can’t forage like a deer.”
Asian Carp
Asian carp (silver and bighead carp) escaped from fish culturists in Arkansas in the late 1970s, and are now present in significant numbers in Kentucky’s major river basins — Mississippi, Ohio, Tennessee, Cumberland, Kentucky, Salt, and Green River.
The problem with a lot of exotics is they have a really high recruitment rate.
“They produce more young so they gain an advantage over our native fish species,” said Jeff Ross, assistant director of the Fisheries Division for the Kentucky Department of Fish and Wildlife Resources. “They are often voracious feeders, too. They eat the same plankton or forage as our native fish species, so they directly compete against them.”
A serious concern is that holders of sport fishing licenses, who can legally take live bait with seines and cast nets from public waters, run the risk of unknowingly spreading the invasive carp species to other streams and lakes in Kentucky.
Young silver carp look remarkably similar to the threadfin and gizzard shad that anglers target for bait.
“Use live bait where you catch it,” said Ross. “Don’t transport live bait to other river systems or any lake. When you’re done fishing it’s best to dump your bait on the shore, just to be on the safe side.”
Art Lander Jr. is outdoors editor for KyForward. He is a native Kentuckian, a graduate of Western Kentucky University and a life-long hunter, angler, gardener and nature enthusiast. He has worked as a newspaper columnist, magazine journalist and author and is a former staff writer for Kentucky Afield Magazine, editor of the annual Kentucky Hunting & Trapping Guide and Kentucky Spring Hunting Guide, and co-writer of the Kentucky Afield Outdoors newspaper column.