Rachel Warren, a school teacher, was taking a nature walk in North Beach with her 5-year-old daughter one morning in August when she noticed jagged edges and strange holes on the leaves of seagrape bushes along the boardwalk.
Warren knew those plants well. As an amateur nature photographer and longtime Miami Beach resident, she had documented many plants and animals during leisurely walks that became more frequent during the coronavirus lockdown. Bug box in hand, the mom-daughter team got ready to investigate and catch whatever was attacking the plants.
“I had never seen seagrape leaves eaten up in that particular way, so I looked closely, thinking I might see some caterpillars,” she said.
But when she looked under the leaves, she saw little black bugs. She didn’t know it at the time, but she had just discovered the latest invasive species in Florida: a glossy black insect known as the black bean bug.
Originally from Asia, the bugs probably arrived recently, and may pose a threat to local crops including sugar cane, hemp and beans, which are the bug’s preferred host plant, the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry said in a pest alert last week.
“We still don’t know if this species will become established here, but we are monitoring this bug closely because it could turn into yet another pest for our crops and ornamentals,” said Paul Skelly, chief entomologist at the division.
After the first sighting in August, Warren posted some photos of the bugs on iNaturalist, an online network for nature enthusiasts to share information about biodiversity. A few weeks later, she was contacted by a University of Florida student, who then forwarded the pictures to the Department of Agriculture.
Agents visited the site in September to collect specimens, which were identified by taxonomists last month as the Brachyplatys subaeneus bug. They are solid, shiny black with thin yellow markings in the shape of a W behind the head. Unlike ladybugs, which feed on aphids and tiny insects that live on plants, the black bean bugs suck nutrients from host plants.
An alert was issued to warn growers that black bean bugs can be damaging to ornamental plants and crops, especially legumes. Other crops like corn, hemp, sweet potato, potato, sugarcane and rice have also been documented as hosts to the black bean bug in habitats where they are more established, the alert said.
Florida has more invasive species than any other state, as its several ports of entry and vibrant trade makes it easy for pests to get here. Even hurricanes and storms can bring invasive species to Florida’s shores. Skelly said his division recognizes an average of 2.5 species of exotic insects that can potentially become established in Florida every single month.
A hospitable climate and plenty of food welcome bugs and reptiles from all over the world. The state is a key gateway for imports of non-native plants and animals, and local demand for exotic landscaping has allowed invasive species to take over large areas.
The Brazilian pepper tree, for example, has smothered acre after acre of local vegetation. The prolific Burmese python has wiped out entire populations of marsh rabbits and other small mammals in the Everglades. And the brightly-colored and spiny lion fish, with its voracious taste for native reef species, is a significant threat to the state’s world-famous recreational fishing industry.
The state is plagued by more than 500 non-native plant and animal species that not only destroy ecosystems but also cost wildlife managers approximately $100 million a year in efforts to control them. And that excludes the damage done by the widespread bug that causes citrus greening, according to Alan Hodges, a University of Florida scientist in the food and resource economics department.
‘Beast of a snake’: Huge python caught in the Everglades sets a new record
How did the black bean bugs get to Miami? In the suitcase of a tourist? On a ship? Blown over in a tropical storm? Scientists don’t know yet. They are also trying to figure out if they are present in other areas or if they just have a small toehold in Miami Beach. The best-case scenario is that this small group will stay around the beach and not “jump hosts” to reach agricultural areas in the state, Skelly said.
“Our hope is that it will hang around for a while and then disappear, like that giant grasshopper in the 1990s, and most exotic insects,” he said. In early 1992, an exotic, six-inch grasshopper with the wingspan of a small bird was spotted in South Florida, triggering widespread concern among farmers. A handful of the Tropidacris cristata cristata grasshoppers, a species normally found from northern South America to Costa Rica, were seen in Miami and Plantation, but disappeared after initial sightings.
The black bean bug, endemic in most Asian countries, was found for the first time in the Western Hemisphere in Panama in 2012, and has since been spotted in Costa Rica, the Dominican Republic and Ecuador.
Following the confirmation of the bug’s ID, a follow-up survey was conducted to determine the extent of the infestation in the immediate vicinity of the initial sighting by Warren. The bugs seem to be moving around: a colony was found attacking some beach bean plants, the ones with pretty purple flowers that grow on the dunes.
“Infestations on this plant appeared to be more numerous than the initial infestation on sea grape and included adults and nymphs,” Susan Halbert, taxonomic entomologist at the Division of Plant Industry at the Florida Department of Agriculture and Consumer Services, wrote in the pest alert. “Further research is needed to more accurately determine the potential geographic range of this invasive species.”
In an Oct. 30 paper published in Insecta Mundi, an open access peer-reviewed scientific journal of entomology, Halbert and other scientists said the invasive bug’s detection is an example of a relatively new but growing trend in early plant pest detection: that of citizen scientists using new technology and social media to share nature images and observations.
“The ubiquity of smartphones with their associated mobile applications (apps) and cameras among the general populace has opened potential monitoring opportunities that may prove invaluable to future early detection efforts,” they said in the paper. And they thanked Warren. “We appreciate her efforts without which we might still be unaware of the presence of this bug in Florida.”
The educator, who is teaching kindergarten and first grade this year, said she is happy to help science protect native plants.
“I didn’t think it was strange to see strange bugs in Florida, but now I know it’s a big deal,” Warren said.