Florida Scientists Fight Pests with Pests

Known as one of the most aggressively invasive non-indigenous plants in South Florida, the Brazilian pepper tree (Schinus terebinthifolius) is about to meet its match. Researchers at the University of Florida have been working since the early 1990s to find an effective control method for the exotic pest plant and are in the final assessment and approval stages of a plan to use sawflies as a biological control agent.

Though sawfly larvae are often seen as pests themselves in many areas of the United States, Florida scientists plan to release sawfly adults – nonstinging wasps – to act as a natural predator to the pepper tree. Initially, the sawflies will be released in a quarantine facility in Fort Pierce, Fla., before being transferred to sites throughout the state.

According to Florida Web site TCPalm.com, in its larval stage, the sawfly eats the leaves of the Brazilian pepper tree, defoliating the tree and leaving it too weak to grow. “They can strip a tree pretty quickly,” notes Jim Cuda, associate professor of entomology at the University of Florida. Cuda has been studying the sawfly since 1998. “We want to have a large population of this insect. We are pretty excited.”

Currently, Cuda and fellow researchers are awaiting permission from the Animal and Plant Health Inspection Service (APHIS) to release of the insect. As with other forms of pest control, the university has gone through an extensive research process to ensure the safety of sawflies as a form of biological pest control. Research has included tests that ensure that both flora and fauna in Florida and elsewhere will not be harmed by the release of the insects. For example, Cuda explains that black birds were studied to ensure that ingestion of sawfly larvae would not be harmful to the birds. Likewise, he notes that tests were performed on other native Florida plant species, such as mangoes, to account for their resistance to the pests.

“Earlier in our research process when we were planning a release, a side issue about toxins in the sawfly larvae came up,” Cuda notes in an interview with Lawn & Landscape. “The toxicity issue had occurred in a different species of sawfly in Australia, but we made sure to do a thorough risk assessment on mammals, as well as nontarget plants. Releases like the one we’re planning should not effect flora and fauna. It took a couple of years to completet those tests and we’ve finally submitted our environmental assessment for field release to APHIS.”

Researchers already have a permit to transfer the sawflies from Gainesville to the new quarantine facility in Fort Pierce, where Cuda says they will soon begin rearing the insects in massive amounts. He says the University of Florida and its research colleagues hope to receive APHIS approval for insect release by the spring, though the timeframe is not definite.

According to Cuda, the Brazilian pepper tree was originally brought to the United States as a landscape ornamental, though it soon overwhelmed its surrounding landscapes, especially in disturbed areas. “Almost a million acres in the Everglades are infested with Brazilian pepper tree because that area had been farmed and was then abandoned,” he says. “The plant took over that disturbed area. Also, if you drive down Interstate 75, I-95 or the Florida Turnpike. You’ll see many more areas of infestation as a result of seeds being blown into that area and also dispersed by robins who eat the seeds.”

Because it thrives in tropical and subtropical environments, Cuda notes that other areas inside and outside of the United States also are experiencing problems with the pepper tree. “San Diego has seen problems recently with the California pepper tree, which is related to the Brazilian pepper tree,” he notes. “It was brought in as a landscape ornamental there, as well, and is beginning to choke out a lot of the native plants. We’ve also heard from researchers in The Bahamas, Hawaii and Texas that are seeing the plant become an issue.”

Though other affected areas may have to do some of their own research, Cuda says the University of Florida researchers are prepare to collaborate with scientists in those areas to create more successful releases of sawflies.

For the Florida area, Cuda says that area land managers, including lawn care and landscape contractors, will eventually gain access to sawflies for control of Brazilian pepper tree on their customers’ properties. “Once we get the releases approved, we’re planning to develop a field insectary site where the sawflies could be collected or redistributed,” he says. “It will be a very formal process that will include training programs and information on how the insect does its job and how to properly apply this type of biological controls. Still, once the sawflies are established, they’ll spread on their own by simply flying to the areas that are infested with pepper tree and. That’s where the host-specificity issue becomes important. We’ve done significant research to make sure that other landscape plants and mammals will not be affected, so we’re looking forward to a successful release.”