How a fly could halt California’s ivy invasion

Cape-ivy, also known as Germany ivy, has been crowding out native plants along the California coast.
Cape-ivy, also known as Germany ivy, has been crowding out native plants along the California coast. National Park Service

Coastal Californians battling pervasive Cape ivy have been waiting years for a helpful fly with a regal name.

Now, Agriculture Department officials are finally getting ready to pull the trigger, turning the fly loose on the weedy vine that’s infested shady parts of the Pacific Coast. The fly deposits its eggs on the Cape ivy, causing a huge boil-like growth known as a gall to form on the plant’s stem and stunt its growth.

For San Luis Obispo County resident David Chipping, it’s about time.

“Invasion of both upland and riparian habitat by Cape ivy long ago reached crisis proportions in our county,” Chipping advised the Animal and Plant Health Inspection Service.

A Los Osos resident and member of the California Native Plant Society’s San Luis Obispo Chapter, Chipping this month added his voice to a handful of others supporting a federal proposal to release of the fly, formally known as Parafreutreta regalis.

Cape ivy is a problem along roadways (and) California’s Department of Transportation (CalTrans) and CalTrans road crews devote time and herbicides for controlling this weed.

Animal and Plant Health Inspection Service

The fly would target Cape ivy, which can climb up to 30 feet, crowding out other coastal plants and requiring frequent herbicide treatments along roadways and in places like parts of Morro Bay State Park.

“Cape ivy is a major problem in coastal riparian areas in California, smothering native vegetation,” warned Gerald H. Meral, formerly deputy director of the California Natural Resources Agency, adding that “an effective biocontrol agent would make a big difference in protecting these areas.”

Meral, now with the private Natural Heritage Institute, and Chipping were among only a dozen or so individuals to offer public comments about the Agriculture Department’s proposal as of Friday. All support the proposed release of the flies to control what’s also been called German ivy.

But the no-drama public comment period, which lasts through April 25, did not come easy. Some underlying studies that supported the proposal began so long ago that the lead scientist has since retired. Research funding has sometimes been iffy. Lab priorities have sometimes fluctuated.

Nor has cost-effectiveness been the only consideration. Under several executive orders, Agriculture Department officials also had to consult with Indian tribes and examine potential specific impacts on children as well as “any minority populations and low-income populations.”

In brief, the wheels have turned methodically. Final approval could still be months away.

“Biocontrol of weeds is always a long process,” retired Agricultural Research Service entomologist Joe Balciunas said in an interview. “I thought this one would go faster, but I was wrong.”

Balciunas and colleagues began testing at an Albany, California-based Agricultural Research Service lab in 2001. Balciunas retired six years ago. A technical advisory panel recommended approval three years ago. The 40-page environmental assessment that likewise concludes the biocontrol program would be safe and effective was completed more than 14 months ago.

“It grinds exceedingly slow,” Balciunas acknowledged.

The vexing Cape ivy is a native of South Africa and was brought into the United State as an ornamental ground cover. Then, it spread, including into areas where herbicide use may be limited. In places like the Golden Gate National Recreation Area, managers resort to hand tools.

“Other methods such as goat grazing and prescribed fire are being used,” the environmental assessment notes.

If left uncontrolled, the ivy becomes a bully. A study at Golden Gate National Recreation Area found that sites infested by Cape ivy for five to 10 years had 78 percent fewer annual plant species than uninfested plots.

Enter the Cape ivy gall fly, which is also a native of South Africa. After mating, the females insert eggs into part of the ivy’s stem. When the eggs hatch, growths known as galls form on the plant and stunt its growth.

Initial plans call for pairs of flies to be placed in field cages over Cape ivy patches in several locations along the California coast as well as Alameda and and Contra Costa counties. In time, the cages would be removed and the flies would disperse naturally.

Michael Doyle: 202-383-0006, @MichaelDoyle10