Here are 5 of the most harmful invasive plants and animals wreaking havoc in Kentucky

The Kentucky Department of Fish and Wildlife Resources has a list of 26 "nuisance species" considered severe threats to the state.

Invasive species are those that are introduced from other parts of the world that adapt and often dominate new areas, due to factors such as having little to no predators, high intelligence and high reproductive rates. 

While more than a couple of dozen invasive species have made their way into Kentucky, there are five in particular the department considers the most threatening: 

Asian carp 

Four major species of Asian carp are found in Kentucky: grass carp, black carp, silver carp and big head carp. 

How did they get here? The fish species is native to southeast Asia. The silver and big head carp first began appearing in Kentucky in the 1970s. Grass carp were introduced in the U.S. around 1963 and escaped in the '70s.

The fish were brought to the U.S. for "different biological control measures," such as controlling snail populations, water reclamation and aquaculture (the breeding and harvesting of fish, algae and other organisms), said Andrew Stump, a biologist at Kentucky's Department of Fish and Wildlife Resources. 

Where in Kentucky are they found? Grass carp are found throughout the Ohio River basin. The furthest up the river black carp are located is in the John T. Myers Pool, near the Newburgh Lock and Dam.

Silver carp occupy several of Kentucky's lakes, including Lake Barkley and Kentucky Lake. Silver carp are also established near Louisville, in the McAlpine Lock and Dam. Big head carp populations extend as far as Pennsylvania because they migrate longer distances. But here in Kentucky, they can be found in large river systems, such as the Kentucky River, Green River and throughout the Ohio River, according to Stump. 

For help identifying different types of carp, use this guide. 

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What do they eat? Grass carp eat larger aquatic plants. Silver and big heard carp are filter feeders and eat plankton and other microscopic plants and animals. Black carp eat mussels. 

What effect are they having on native wildlife? The variation that has been most impactful is the silver carp. They colonize rivers rapidly and "muscle out and move into spaces where native species are," Stump said. They take up space and eat much of the plankton native species rely on.

Black carp eat already endangered, native mussel species. Grass carp "can really strip off banks of neutral buildup of healthy vegetation," which some fish use as protection and helps diversify the bank's active species, Stump said. When native vegetation is stripped, other invasive species, like hydrilla, can move in and make the area homogenous. 

What is being done about them? The fish and wildlife department has monitoring and containment programs for the carp, in which it surveys areas to see where populations are expanding or decreasing. It also allows contract and commercial fishing in some areas to help control the species. 

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Zebra mussels

How did they get here? The zebra mussel is native to the eastern European region, in the Black and Caspian seas. It was introduced to the U.S. in the mid-to-late 1980s. Mussels were released by container ships dumping water. They first showed up in Kentucky in 1991 and spread through larger river systems.

Where in Kentucky are they found? They are located throughout the Ohio and Kentucky rivers. The species does not adapt well to high-flow bodies of water, so the state's dam systems have helped the mussels flourish. 

What do they eat? They are filter feeders and mainly eat plankton. 

What effect are they having? Zebra mussels compete with native wildlife by taking up valuable nutrients and space. They can also affect water chemistry, causing algae blooms. The mussels have also had significant commercial and aesthetic impacts, as they attach to hard surfaces and other animals in large numbers. They can get stuck in pipes, on boats and motor systems and cover beaches, which may affect access. 

What is being done about them? The department recommends you "clean, drain and dry" and inspect equipment. It is also effective to disinfect surfaces that have been around water.

Chemical treatments may also be applied. However, Stump said the department's education and outreach approach has been very efficient and helped stop the organism from moving into internal lake systems.

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Wild pigs

Where did they come from? Common wild pigs are hybrids of domestic farm pigs and Eurasian wild boars. The Eurasian wild boars were brought to the U.S. by settlers in the 1500s to provide more hunting opportunities, according to Terri Brunjes, a biologist with the Kentucky Department of Fish and Wildlife Resources. 

Where are they found in Kentucky? There are several isolated populations of the pigs throughout the state. However, the Kentucky Department of Fish and Wildlife Resources does not share specifics of the pigs' location to try to curb hunting of the animals. "It interferes with our eradication efforts," Brunjes said. 

What do they eat? Wild pigs eat pretty much anything, Brunjes said. Their main diets include plant matter, such as roots, tubers and corn crops, as well as earthworms. However, they also eat acorns, frogs, salamanders and disrupt ground-nesting birds by eating their eggs. 

What effect are they having on native wildlife? "They are the perfect invasive species," Brunjes said. "They are highly intelligent. They have high reproductive rates, no natural predators. They can eat anything, and they can live anywhere...They are one of the greatest natural resource challenges we face."

The pigs' diet causes increased competition for food in areas where they are present. They drive out deer and turkeys, destroy forest floors by digging and disrupt water quality by wallowing. 

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What is being done about them? Kentucky is one of the only states in the southeast where the wild pig population is declining, due to the state's aggressive trapping program, according to Brunjes. In problem areas, remote-controlled traps and cameras are put in place. Biologists must monitor how many pigs are present in the area and trap them all before closing the trap door. Otherwise, if only a few are caught, the others are smart enough to leave the area or become "trap shy," Brunjes said. 

Kentuckians also should not shoot at the pigs. "You may kill one or two, but you've educated the rest," she said. "They become nocturnal, they leave the area, they avoid all human activity, they avoid traps, and then we can't find them again. So, by the time we catch up with them, all the females in that group have had another litter. You end up with more pigs you removed to begin with.”

Instead, Brunjes urges those who spot a wild pig to report it to the department by visiting this site and clicking "report." The department also provides free, professional pig tracking services.

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Hydrilla

Where did it come from? The plant, also known as water thyme, is native to Asia. It was first brought to the U.S. in the 1950s for use in aquariums. Variations of the species began showing up in Kentucky as early as 1999. 

Where in Kentucky is it found? The plants are prominently located in the state's Western Fishery District, near Kentucky Lake, and in the Eastern Fishery District, in Dewey and Paintsville lakes. They are also in the Ohio River and Cave Run Lake, about 70 miles east of Lexington. 

What effect are they having on native wildlife? The plant is able to reproduce asexually, using only female or male parts, and vegetatively, meaning fragments of the plant can begin a new colony.

"They tend to just choke out large stretches of bank where they just have sufficient access to light," Stump said. "So, no matter what is growing there, they sort of just take over and create this monoculture in the systems that they infect." 

What is being done about them? The state’s Department of Fish and Wildlife Resources has district managers who report problem areas, Stump said. Efforts to combat the plant largely rely on early detection. The area is then treated with herbicides.

“It is surprisingly resistant, and there are even some strains of hydrilla that are completely resistant to some of the most effective herbicides that you can use on it,” Stump said.

Even if the herbicide is effective on the foliage of the plant, it has a network of tubers that allow the hydrilla to easily reestablish itself.

If you encounter the species, never transport it. Don't dump bait or water from one location to another, as fragments of hydrilla can mingle with it. The department also recommends you inspect and "clean, drain, dry" your fishing and boating equipment. 

For the department's full boating and fishing guide, click here. 

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Bush honeysuckle 

Where in Kentucky is it found? The plant can be found throughout Kentucky, but the

"problem areas" are in the central region of the state, such as Louisville, Lexington and surrounding counties, according to biologist Ben Robinson.

How did it get here? The bush honeysuckle plant is native to northeast China, Japan, Korea and far east Russia. It was first brought to the United States in 1898 for use in the New York Botanical Garden. It has been used for wildlife cover, soil erosion control and as a decorative bush. It began spreading into natural areas and reproducing on its own, according to the Kentucky Native Plant Society.

What effect is it having on native wildlife? The plant spreads easily; its seeds are carried mainly by birds and other animals. It is also extremely flexible and can grow "just about anywhere," Robinson said, including the sides of rocks or in heavily shaded areas. Because of this, the plant chokes out understories of forests, which creates increased competition for native plants. 

What can be done about it? "It's really hard work to get rid of it," Robinson said. It's not impossible to eradicate the species in places it shouldn't be, but in order to fully do so, it requires cutting the plant and treating the source with herbicide. You're not done there, though. Follow-up treatments are necessary, and because the plant is so widespread, it can be a tedious and labor intensive task.

Financial assistance is available through the U.S. Department of Agriculture for homeowners trying to get rid of the flower. To get more information, contact Private Lands Coordinator Jacob Stewart at jacob.stewart@ky.gov, or 502-892-4412. 

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Contact Ayana Archie at aarchie@courier-journal.com or follow on Twitter @AyanaArchie. Support strong local journalism by subscribing to The Courier Journal.