Leopold Center - Hopping beetles may help Iowa get jump on weed pest

It’s a battle of David versus Goliath, a tiny hopping beetle versus the “scourge of the West.”

But the team of scientists, educators, livestock producers, wildlife managers and others working with the Leopold Center are betting on the beetle. To ensure an eventual victory, they plan to launch a campaign this year to raise thousands of these friendly beetles in Iowa to fight the intruder. Their second weapon will be education – using at least five insectary sites in and around Woodbury, Plymouth and Sioux counties to educate people about the extent of the problem.

The enemy is a non-native perennial, leafy spurge (Euphorbia esula). It is very aggressive and invades an area by choking out native vegetation. Infestations can destroy grazing lands for cattle and horses, reduce plant diversity, degrade wildlife habitat and displace sensitive species.

The plant can dominate landscapes within two to three years – from open prairies and hillsides to riparian areas and lowlands. It is believed to infest more than five million acres of land in 35 states and the prairie provinces of Canada. The amount of forage estimated to be lost each year to leafy spurge in the Dakotas, Montana and Wyoming could support a herd of about 90,000 cows.

Project began with inquiry at public meeting
Although the weed is not new to Iowa, its prevalence has increased in recent years, says Iowa State University Extension entomology program specialist Rich Pope. He is co-leader with entomology professor Jerry DeWitt of a three-year special project at the Leopold Center.

The project began in 2003, after Leopold Center director Fred Kirschenmann was asked about the weed’s impact in Iowa. Further checking showed that leafy spurge was established in northwest Iowa and was beginning to appear statewide.

“This species is very good at filling a niche, especially where there’s a long-term lack of disturbance,” Pope said. “With no-till, the CRP program and other changes in the way we manage land, leafy spurge has gotten a foothold in some areas.”

Pope said the “epicenter” in Iowa is in northwest Woodbury County, also in Sioux, Plymouth and Monona counties. This region has less row-crop production and more pastures than other parts of the state, and a number of natural and non-managed areas, including the Loess Hills.

In the initial year of the project, ISU Extension weed specialist Bob Hartzler conducted a random survey of 20 roadside tracts in Monona, Dickinson and Ida counties. He found infestations in 5 percent of the Ida County tracts and 15 percent of the Monona County tracts, which could indicate an even higher infestation in selected locations.

Cultivation and application of herbicides can reduce leafy spurge, but are not desirable for grazed areas. Goats and sheep will eat the plant, but this method of control has limited success in recreational or environmentally fragile regions such as the Loess Hills. Intensive grazing also can delay re-establishment of native vegetation.

Biological control a good option
The good news is that leafy spurge is tailor-made for biological control – in this case, beneficial insects that feed on the weed pest.

Farmers, researchers and wildlife managers in other states and in Iowa have had considerable success reducing leafy spurge infestations by introducing two species of flea beetle (Aphthona nigricutis, Aphthona lacertosa) and the red-headed longhorned beetle (Oborea erythrocephalis) in an infected area.

These insect species are host-specific – they feed only on a narrow range of hosts restricted to the spurge family. Flea beetles feed on roots and foliage while longhorned beetles are stem-miners – they eat and lay eggs in the stem and bore into the root crown as larvae.

Flea beetles emerge in late May or early June. They are black, shiny and about 1/16 of an inch in length. They hop, hence, the name flea beetle. They are not the same species that is a pest in corn.

As a pilot release and to begin rearing insects for future uses, ISU entomologists released 15,000 flea beetles at three Sioux City sites in 2003 – two within Stone State Park and one on private property near the park. They also released 50 longhorned beetles along railroad property in Hamilton County.

The beetles will find company in the 1,000-acre park typical of the Loess Hills of western Iowa. Park ranger Kevin Pape has been marshaling the troops with his own releases of the beneficial insects.

Infestation grows in public areas
“I’ve been trying to control leafy spurge since I came here 13 years ago,” Pape said. “At first I tried herbicide, which I never thought I’d be using as a park ranger, all applied very carefully using a backpack sprayer and walking the park’s steep ravines.”

About three years ago, he began releasing beetles throughout the park. Although he hasn’t tracked each release, Pape said there’s a good distribution of the insects, judging by the smaller size and number of leafy spurge patches in the park.

“If I would have done nothing, leafy spurge would have overtaken some areas of the park,” he said. “It’s really unique because it invades natural habitats so readily. Typically a weed needs some disturbance to thrive, but not leafy spurge. This plant is a big threat to our prairies in the Loess Hills.”

Pape said education is a big part of the effort. He’s helped nearly a dozen neighboring landowners get flea beetles to release on their own property, which also is infested with leafy spurge. He’s also worked with The Nature Conservancy and county conservation board to sponsor nature hikes and public meetings to help people learn about the problem. “I’d say a vast majority of people don’t even know what leafy spurge is, or that it's a threat,” he said.

Bud Vogelzang of Sioux Center, who owns land in Lyon and Sioux counties and farms part-time, agrees. “Each year I find new and different patches in my terraces, so it’s a constant battle,” he said. “A lot of good farmers don’t know what it is.”

Jon Mitchell, director of facility services at Briar Cliff University in Sioux City, has been fighting spurge in one of the city’s largest infestations, a five-acre hillside that overlooks the college and a large tract of native prairie.

When a maintenance worker began cutting the plants to tidy the campus for graduation last fall, Mitchell heard about it. People liked its flowers, which had become somewhat of a college landmark on the steep, unmowed embankment.

“The hillside is gold and gold is one of the school’s colors,” Mitchell said. “For all I know, someone planted it there for decoration. I don’t think anyone realized it was a problem.”

ISU’s Pope said Briar Cliff University and other public areas would be great places to release and raise flea beetles, and to set up a targeted education and outreach effort. But he cautioned that biological control is not an immediate fix. “It may take four or five years to get the infestations under control,” he said. “There’s no silver bullet but this looks like the long and smart solution.”