Seven Deadly Invasive Species

As the world becomes more connected and we move ever more material and people in between continents, invasive species are the occasional hitchhikers and living biohazards produced by the system. These creatures have travelled a long way from home, and once they arrive in sunny South Florida, they’ve escaped the predators that usually keep them in check, thriving on new prey and carrying new diseases with them. Just like Columbus entering the new world, these invaders spread the equivalent of smallpox, devastating the local environment.

Giant African Snail

While they begin as pea-sized eggs, the giant African snail (Lissachatina fulica) will eventually grow a shell over seven inches in length. In South Florida, it takes this massive land snail only six months to reach reproductive age, at which point they will begin popping out about a hundred eggs per month. Starting from but one snail, an area’s population can skyrocket to thousands in less than a year. To fuel this rapid growth, the snails have a ravenous hunger, chowing down on over five hundred varieties of plants, with a preference for the soft flesh of delicious fruits or vegetables, as well as the most tender shoots of fresh growth and flowers. To make matters worse, their slime carries the rat lungworm (Angiostrongylus cantonensis). A smear of the snail’s slime on your hands or unwashed produce could be enough to infect you. The lungworm burrows its way into your brain, where it dies, releasing bacteria that can cause a particularly virulent form of meningitis that can lead to blindness, ataxia, and even death. The good news is that while a number of snail infestations have been identified throughout the Miami area, the Florida Department of Agriculture and the USDA have already successfully turned the tide on this invader. Help win the war against this treacherous snail by calling the Florida helpline at 1-888-397-1517 if you see one in your area.

Everyone knows the pythons in Florida are a problem, specifically the Burmese python (Python bivittatus). While not the only constrictor of concern, Burmese are among the most abundant in the Everglades, and one of the largest. Captured Florida specimens have been found that were longer than 17 feet, and there is increasing evidence that as an apex predator, they are directly responsible for the disappearance of small mammals in the Everglades. While the 2010 frost did a number on their population, the snakes have rebounded and are increasingly encroaching on urban Miami. A related species, the African rock python (Python sebae) was caught eating a sixty-pound husky in Kendall. They are ambush predators, striking from concealment, and are well-suited to the rough country of the Everglades. This natural camouflage and hiding ability in remote and inaccessible territory makes it extraordinarily unlikely that hunting would ever be able to actively impact their populations now that they are firmly established in South Florida.

The single gravest invasive threat facing Florida remains the Asian citrus psyllid (Diaphorina citri) and the citrus greening bacterium (Candidatus Liberibacter sp.) it carries. Citrus greening is a bacterial disease that is gradually wiping out not just the Florida citrus industry, or even the American citrus industry (after spreading to Texas, Mexico, and California), but the entire global citrus industry, with infestations raging in China, Brazil and across Africa. The psyllids carrying this plague are tiny insects that look a little like black and white flags. First detected in Florida in 1998, there are now trillions of them flying around the state. It takes only one infected psyllid to spread the bacterium from an infected tree to a healthy tree, at which point, most trees in the family Rutaceae, which includes rare and endangered native plants related to commercial citrus, have between five to eight years left on the clock before the bacterium overwhelms them. Symptoms of citrus greening include bitter, misshapen fruit and an uneven yellowing on the leaves that has earned the disease the nickname “the yellow dragon.” There are a number of possible treatments in the research pipeline, but at this point, there is no real solution for infected trees and the outlook for Florida citrus as a whole is dire.

Redbay ambrosia beetles Xyleborus glabratus carry the deadly laurel wilt fungus (Raffaelea lauricola) in special pockets in their mouthparts. Another species from Asia, this minute beetle is a fungus farmer, burrowing into the sapwood of trees, where it lays its eggs and tends its fungal gardens. While trees in the beetle’s native range in southeast Asia have adapted to tolerate the fungus, our native trees from are highly susceptible to the fungus, dying within six months after infection by just a single beetle. After the beetle was first detected in Savannah, Georgia, in 2002, it has spread across the American southeast, leaving whole forests of native redbay trees empty in its wake. The beetle spread throughout the United States faster than it could ever have on its own because people irresponsibly and illegally transported firewood from areas with sick trees to new areas with healthy trees. The beetle first arrived in South Florida by 2010, and the fungus was first collected from dying redbay trees almost a year later in 2011. The beetle also feeds on other plants in the laurel family, including Florida’s beloved avocado trees, which are just as susceptible to the fungus. Both backyard trees and commercial groves are already dying across South Florida. This was a preventable disaster, and it threatens the state’s entire avocado industry.


Originally from the Philippines, the lionfish (Pterois volitans) is beautiful, but dangerous. Their exotic good looks make them popular in aquariums, but there are no predators or diseases to limit the growth of their populations in Florida waters. As a result, they are growing to an unprecedented monster size relative to their Philippine ancestors, devouring other reef fish throughout the southeastern coasts of the United States. Their rapacious feeding has been endangering native commercial fish stocks at spawning sites, while destabilizing the rare and delicate coral ecosystems of our Florida coasts. These creatures are only here to wreak such havoc because irresponsible pet owners have released them into the wild, which is illegal under both Florida and Federal law. If you find yourself with a lionfish, or any other exotic pet, that you can no longer care for, there are alternatives. The Florida Fish & Wildlife Conservation Commission collects unwanted pets at Exotic Pet Amnesty Days held across the state, where they’re examined by vets and released for adoption by a new pet owner certified beforehand by the commission as caring and responsible.

The medfly (Ceratitis capitata) is originally from North Africa, but global trade has spread these little monsters around the world. They repeatedly threaten Florida agriculture, after accidentally being smuggled past customs inspectors from South America and the Caribbean. It is only because of the constant vigilance conducted by a defensive monitoring program in collaboration between the Florida Department of Agriculture and the USDA that medfly has yet to become permanently established in Florida. Medflies lay their eggs beneath the skin of over 260 types of fruits, nuts, and vegetables, ranging from blueberries to peaches to oranges. It takes only three weeks to complete their life-cycle. One female can infect a single fruit with dozens of baby maggots and still have hundreds of eggs left over. Once her maggots emerge from the wreckage of the fruit, they fly away to wreak their havoc on neighboring plants up to 20 miles away. Whenever this fly is detected by Florida’s statewide monitoring program, an immediate eradication effort is launched, including pesticide sprays, the destruction of all host fruits within the infested zone, and the release of sterile flies to disrupt mating. Infestations would occur far less often if visitors didn’t accidently pack the pest with them by travelling with fresh fruits and vegetables from outside of the country. Another step you can take to help prevent medflies is to buy local, reducing the chances of infection from produce grown outside the state. Always look for the “Fresh From Florida” logo.

Brazilian pepper (Schinus terebinthifolius) is one of the most successful Florida invaders. Once imported to grow peppercorns, the plant escaped cultivation, becoming so abundant some folks call it “Florida Holly” due to its bright red berries at wintertime. A tall and shrubby plant, it aggressively chokes out all other plant life in the area, transforming thousands of acres into a massive and impenetrable monocultural thicket of nothing but Brazillian pepper. It even secretes compounds that repress the growth of other plants. Managing Brazillian pepper overgrowth requires long and grueling physical labour and herbicides to suppress populations. Worse, the weedy bush produces thousands of bright red berries, which are irresistible to birds, who often carry them for hundreds of miles before dropping the seeds, often back onto previously cleared areas. You can help fight this invader by refusing to planting it and by destroying any saplings that might appear in your yard.

By Andrew Derksen
Andrew Derksen is an invasive species biologist who loves coffee, chili peppers, and armadillos. As an expatriate Texan, he habitually fights lost battles at his own private Alamo - and sometimes he even wins them.