Photos courtesy of UCSB Marine Science Institute research biologist Tom Dudley A female Tetramesa romana deposits eggs into arundo shoots. A study is under way to determine whether the wasps can be used in a larger effort to eradicate arundo.

As it turns out, the biologist only had to go as far as the Santa Clara River in his hometown of Santa Paula. It is there that Dudley thinks he's found something to help combat the weed that has taken over countless miles of rivers in Ventura County and cost millions of dollars to eradicate across the West.

Dudley and other biologists at the UC Santa Barbara Marine Science Institute found a tiny, non-native wasp that lays eggs in the stems of arundo, which leads to weakened plants. Weak plants are susceptible to other pathogens that could kill the plant and stop its spread.

The wasp isn't capable of stinging people, he said.

"There are good aliens and bad aliens," Dudley said. "Arundo is the bad one, so we are going to bring in the good ones to knock them out."

Scientists around the country are working on ways to stop the weed that chokes waterways, sucks up valuable fresh water and forces out native plants. Ventura County recently launched a $5 million project using chemicals to try to rid Matilija Canyon of the plant.

A team of researchers in Texas was working on importing the wasp from Europe — where it, and arundo, come from — when Dudley found some of the bugs boring into arundo stalks at a 20-acre study site on the Santa Clara River. He, too, had been looking far and wide for a bug that would harm the arundo.

After more exploring, Dudley found the tiny wasp, Tetramesa romana, all around California's south coast.

"It's a really big step that this is already here and quite widespread in Southern California," he said.

The problem is that arundo populations are terribly dense in some areas, so the wasps aren't doing enough damage. And they aren't a silver bullet, Dudley said.

The wasps' boring into the stem weakens the plant but doesn't completely kill it. The best way to get rid of the plant is to have the wasps do their work while another pathogen, such as a fungus, is introduced to finish off the arundo.

Dudley is studying the wasps around Ventura County and plans to introduce some to the Santa Ynez River in northern Santa Barbara County to determine the impact.

He said tests in the laboratory show the wasp doesn't feed on other plants and doesn't compete with other native bugs.

Because the wasps already live in this country, they could be used across the West within five years, Dudley predicted. Still, regulations could easily double that timeline, he said. If he gets permits and funding, he'd like to introduce more of the bugs around the West in larger populations so they could help tackle the arundo problem.

Jeff Pratt, director of the Ventura County Watershed Protection District, which is overseeing the arundo removal program in Matilija Canyon, said any solutions to the problem are good.

"It's viewed by everyone as noxious and out of control," he said of arundo. "This is a tremendous pest. Anything that is more environmentally friendly or less costly would be welcome."