An invasive butterfly that damages citrus trees has reached Florida
It is speculated that the species moved into Key West as a result of Hurricane Ian.
The lime swallowtail butterfly — an invasive species that hails from Asia and which has damaged citrus trees throughout the Caribbean for nearly 20 years — has reached Florida.
The butterfly is fairly large, with a wingspan of nearly four inches, similar to that of a monarch, and can be quite beautiful, as if Jackson Pollock made black-and-white splatter paintings across their wings and added a bold red dot at the base.
The butterfly’s various larval stages ravenously consume citrus foliage, which can expose fruit to too much sunlight, and weaken the tree.
Last fall, residents in Key West found specimens on their backyard citrus trees, and the Department of Agriculture swept in.
“We had a homeowner who was a butterfly aficionado and took a picture ... that’s what kicked things off,” said Trevor Smith of the Florida Department of Agriculture and Consumer Services. “I sent a team down immediately.”
State officials collected the suspicious larvae, conducted DNA sequencing and concluded that the Key West bugs were indeed the destructive culprits from the Caribbean.
Since then, the state has broadened its search to the middle and upper Keys and not found any lime swallowtails. “It’s only in Key West that we’ve found any, and in the last two surveys, we haven’t found any,” Smith said.
Lime Swallowtails, indigenous to Asia, first showed up in the Dominican Republic in 2004, made their way to Puerto Rico in 2006, and have since flitted their way to Jamaica, the Virgin Islands, Cayman Islands and Cuba.
How much damage can the lime swallowtails do? The larval stages are when they do the damage, and they spend their whole lifecycle on one tree. Early larval stages look like bird droppings, but later stages are large and green.
Jamaica’s Ministry of Agriculture and Fisheries website says, “The lime swallowtail butterfly … is known to destroy citrus plants in Jamaica. The pest eats the leaves of orange and ortanique trees, leaving the fruits open to the sun.”
According to the California Department of Food and Agriculture, lime swallowtail larvae consume large amounts of foliage and can seriously damage host trees.
“This is of special concern to citrus nursery stock, as young citrus trees are most severely affected by larval feeding,” the site says. “Severe infestation causes tree defoliation and can even lead to growth retardation and decreased fruit yields.”
How did the invasive butterflies get here? Smith has a hunch, but no proof.
“This is purely speculation, but this species is in Cuba, and at one point Hurricane Ian was literally straddling Key West and Cuba at the same time,” Smith said. “Looking at the numbers, and how small this population is, I wouldn’t be surprised if this wasn’t something that was moved over by the hurricane.”
It’s not yet clear if there are enough lime swallowtail here to make a viable population. “We had a really small population, and we jumped on it so quickly that we might already be at a point where it’s not a large enough population to be viable,” Smith said.
If the species did eventually establish a successful breeding population in Florida, Smith said he thinks it would be a minor pest. “For backyard citrus, this could be a real pain for people,” he said, but not so much for the citrus industry. “Most of your commercial growers right now are hitting citrus so hard with pesticides to deal with all these different diseases, they have a pretty stout defense set up. I don’t think this butterfly would make any inroads there.”
Coming to America
North America has been fertile ground for invasive insects before. Most recently, the spotted lanternfly, which hails from China, has sent authorities in the northeast into a tizzy. Officials have urged people to kill them on sight.
According to the USDA website, the spotted lanternfly first showed up in Pennsylvania in 2014. “If allowed to spread in the United States, this pest could seriously impact the country’s grape, orchard, and logging industries,” the site says, and boasts flyers with slogans such as “Join the battle. Beat the Bug,” and “Stop. Scape. Squash.”
The spotted lanternfly has spread throughout the mid-Atlantic and into New York state and Southern New England, and can weaken and sicken more than 70 species of tree by feeding on their sap.
If you find a lime swallowtail
If someone finds a larvae or a butterfly, they should get in touch with the Florida Department of Agriculture and Consumer Services plant division at www.fdacs.gov/Divisions-Offices/Plant-Industry.
Smith advised that if the larvae is on a citrus tree in Key West, go ahead and collect it and put it in a jar in the freezer so his team can examine it at a later date.
Though there’s some concern that people might confuse the lime swallowtail with the endangered Schaus’ swallowtail, Smith said it is safe to collect specimens in Key West because the Schaus’ swallowtail does not exist there.
“If it’s on a citrus tree, just go ahead and take a sample,” he said. “Having those extra eyes out there doing the work is critical.”
Local birds and reptiles, too, can make a difference.
“Those animals can be very effecting with invasive insects — when you have these small numbers (of invasive butterflies), something as simple as a gecko eating a few of these caterpillars could change the whole nature of whether this population can establish,” Smith said.