Beetles to the Rescue

February 1, 2015, Department, by Richard J. Dolesh

Lilioceris cheni, the Nepalese beetle that is providing bio-control of air potato vines in Miami-Dade County nature preserves, munches contentedly on one of the invasive plants.Just imagine if one day you discovered a new plant species in your local park. You have never seen this climbing vine before, but suddenly it’s everywhere and growing like wildfire. You call it the “air potato,” although it is nothing like the well-mannered vegetable that knows its place in the soil and stays there, producing plump nourishing tubers. Your air potato is aggressive, invasive and destructive to natural ecosystems. If you live in South Florida, this not a dream — you have them all over your nature preserves, and they are expanding their range and damage.

Air potatoes (Dioscorea bulbifera) are invasive plants that originally came from Asia. They are twining vines that latch on to trees, shrubs and virtually anything that is upright. They grow at an astonishing rate of 8 inches per day and can grow up to 80 feet per year. When they reach the top of taller trees, they intertwine in tangled green mats, blocking out sunlight and nourishment for everything below. Air potatoes form a dense canopy that by its sheer weight can bring down even healthy vigorous trees. Worse, as they grow to maturity, air potatoes drop hard little bio-bombs called bulbils that spread the plant. In some areas, air potato bulbils cover the forest floor so thickly that you would be likely to crush one with every step you took! And every bulbil — from the largest, which can grow to the size of a grapefruit, to the smallest, which can be tinier than a pencil eraser — is capable of propagating new vines when it extends tubers into the soil. 

So, who are you going to call if air potatoes invade your parks? Well, if you live in Miami-Dade County, Florida, an area of the country that is ground-zero in the nationwide fight against invasive plants and animals, you will be very glad to know that your county park and recreation department has a Natural Areas Management unit composed of biologists, ecologists and park managers dedicated to reducing and controlling the spread of invasive plants and animals in 80 natural area park preserves. 

To give some perspective of how problematic invasive species in the United States are, the cost of dealing with them now approaches $140 billion per year. Florida alone spends more than $100 million annually on invasive species. Controlling invasives on public lands and in nature preserves is even more difficult when simultaneously trying to protect rare natural ecosystems. The damages to parks are more ecological than economic. According Dr. Min Rayamajhi, a plant pathologist with the United States Department of Agriculture (USDA) Agricultural Research Services Invasive Plant Research Lab, invasive species displace native wildlife and destroy ecological balance. And South Florida is in danger of irrevocably losing a remarkable variety of native plants and wildlife that are rapidly disappearing because of invasive species.

Park Preserve Proposed as Bio-Control Site to Combat Invasive Air Potato

When it came to fighting the advance of the air potato, Eduardo Salcedo, an environmental resources project supervisor for the Miami-Dade County Parks, Recreation and Open Spaces Department (MDCPRD), had a good idea. He knew the USDA was looking for bio-control test sites, that is, areas carefully selected to deploy a type of highly selective plant pest to control the damages from a particular invasive species. Rayamajhi and a colleague discovered a type of beetle (Lilioceris cheni) in Nepal that appeared to eat only air potato vines. USDA began a rigorous testing protocol on the species for potential use as a bio-control agent for this plant.

When Salcedo heard about USDA’s interest in establishing test control sites, he led the effort for MDCPRD to propose Kendall Indian Hammock Park as a possibility. But Salcedo, who was originally instrumental in bringing students to the park to teach ecology, went a step further. He asked his brother, Alex Salcedo — a lead teacher of environmental science at the nearby Miami-Dade County magnet high school, TERRA Environmental Research Institute — if he would like to involve students from TERRA in the research.

Students Enthusiastic; Administrators, Not So Much

There was resistance at first. The school principal was skeptical. Even though the park was a walkable distance from the school and she was not opposed to kids leaving the grounds for science education, she was concerned about taking kids out to a heavily wooded park containing many natural hazards — poisonous insects, poisonous plants, spiders, snakes and more. Alex Salcedo said he had to work with the school administration to overcome concerns but, in the end, the principal agreed and has now become very supportive of student involvement. 

Rayamajhi was skeptical as well. He said, “I don’t really have time for this,” but as a research scientist who is very aware of USDA’s commitment to stimulating young scientists through STEM (science, technology, engineering and math) education, he was willing to take a chance, especially when he saw the enthusiasm of the students. In fact, as the students became increasingly engaged in the project, new ideas about how they could contribute flourished and new partners emerged, such as the Darden Foundation, which volunteered help and financial support, and the State Farm Youth Advisory Board, which provided funding for materials and supplies. 

What began as field study and class projects has evolved into much more. Based on the early success of the collaboration, MDCPRD worked with the USDA Invasive Plant Research Laboratory and the teachers and students at TERRA Institute to set up a school lab where the students themselves could raise thousands of beetles for release in the park and other areas to control air potato vines. (Visit the TERRA Institute’s video stream to take a closer look at the students’ project.) Junior Micaela Divico says, “I got involved in the project because I became fascinated with the beetles. How could they eat so much?” Gabriel Caceres, also a junior, says he became interested because he is concerned with saving the environment. 

When asked to identify the most valuable part of being involved with this project, Micaela says, “The most valuable thing for me was what we gave back to the community. We are giving them back this park. It gives me a great feeling.” Eduardo Salcedo says adding students to the project changed everything. “It has been worth all the effort. It makes all our work so meaningful.”

Richard J. Dolesh is NRPA’s Vice President of Conservation and Parks.