An invasive giant reed plaguing ecologically important areas in the United States may find itself buzzing off, thanks to the discovery of a wasp in the Santa Barbara area.

The University of California Exotic/Invasive Pests and Diseases Research Program funded a project to research the impact of the giant reed, Arundo donax, on ecosystems and to find host-specific control agents for the plant. UCSB researchers are currently studying a certain species of herbivorous wasp found in Santa Barbara, the Tetramesa romana, which acts as a reed control system.

According to UCSB’s Marine Science Institute Riparian InVasives Research Laboratory, the California Dept. of Food and Agriculture recently declared Arundo a “noxious weed” and the giant reed is considered one of the top five invasive species harming California’s ecosystems.

However, researchers have found a weapon – Tetramesa romana wasps. The wasps, which were unintentionally introduced in Southern California, closely resemble their Mediterranean counterparts.

By keeping the reed population low, these wasps offer an effective resistance to the plant, while maintaining a very low impact on the ecosystem at large.

The United States Dept. of Agriculture has sought a solution to the reed problem, and was seriously considering spending money to import insects from Europe. However, with the discovery of the Tetramesa romana wasps locally, such measures may not be necessary.

The problem with the reeds is not new. MSI RIVR Investigator Tom Dudley said the Spanish originally imported Arundo to North America in the 1820s from the Mediterranean region, aiming to prevent erosion around farmlands.

“The reeds have existed here for about 200 years, but have only really been recognized as a problem within the last 20 years,” Dudley said. “They have recently become far more abundant and problematic.”

The reed infests areas quickly and obstructs rivers and streams, changing ecosystems and increasing the potential for fires in these areas. The reed absorbs massive quantities of water, yet still remains flammable.

“Riparian areas [land adjacent to a body of water] used to be a good blocking system for wildfire movement, [but] with all these exotic plants, we’ve turned these riparian zones into areas where wildfires can move right across,” Dudley said.

In addition, the giant reed also steals nutrients from the native plants that provide vital food supplies and nesting areas for the native wildlife. As a result, these reeds can flourish here at great cost to the local plants and animals.

“The Arundo tends to respond to nutrient increases better than the native vegetation does, and our experiments have shown that they have a greater growth response than the native plants,” Dudley said.

In light of the discovery, researchers will continue observing the wasps to see if the wasps can contain the spread of the giant reed without outside insects. Researchers will examine wasps’ effects on the reed infestation in Santa Barbara in order to determine if the wasps could potentially assist in combating further spread of the reeds elsewhere.