For the week of May 14 - 20, 2003

Knapweed planted
for habitat

Weevils to join noxious weed fighting effort

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By GREG STAHL
Express Staff Writer

In a strange twist of an ongoing battle against noxious weeds, Blaine County’s weed warriors last weekend carefully planted, watered and tended to approximately 160 knapweed sprouts.

"We’re not planting knapweed. We’re planting habitat," declared Nan Reedy, director of the Southern Idaho Biological Control Program.

Planting knapweed, Blaine County Weed Department Outreach Coordinator Don Wright, insectary maintenance manager Britta Grimberg and Southern Idaho Biological Control Program Director Nan Reedy, left to right, tend to the young sprouts that will be used to raise knapweed-eating insects. Express photo by David N. Seelig

The sprouts, each an inch or 2 tall and about 3 inches in diameter, were planted in several neat, tomato-like rows in a remote corner of the Valley Club, where they will be nurtured to maturity.

Knapweed is among the top invasive species in Blaine County, drawing significant time and money in annual efforts to eradicate the resilient menace. But the knapweed gardening project is intended to add to the local knapweed fighting arsenal by using the plants to raise Cyphocleonus achaetes and Lorinus Minutus, two non-native root-boring weevils that have been approved by the United States Department of Agriculture for use in the war against knapweed.

Later this summer, as the weeds reach maturity, the project’s focus will shift to the insects. The plants will be surrounded by metal fencing and covered with mosquito netting, and the weevils will be added.

Reedy explained:

The weevils will mate and lay millions of eggs. They’ll hatch, and the larvae will bore into the earth, where they will winter and feed on knapweed roots. By next July, some of the adult insects will be harvested to eat knapweed roots at carefully monitored sites elsewhere in Blaine County.

It’s a program that has been enjoying successes on the Camas Prairie since 1998. There, at the Camas Bug Crew’s nine test sites, knapweed stem counts have been reduced by two-thirds, and species diversity is on the rise, Reedy said.

On Saturday, May 10, Reedy, Blaine County Weed Department Outreach Coordinator Don Wright, insectary maintenance manager Britta Grimberg and several Wood River Middle School Eco-Club members tended to the plants. This summer Grimberg and the students will continue to raise the weeds and insects.

This summer, Grimberg and the students will collect baseline vegetative data on five to 10 local sites, introduce the insects and continue to monitor the plots for a minimum of five years.

"My motivation is giving back to Mother Earth," Grimberg said. "Let’s do away with the chemicals. I know this is a five-year process, but hopefully we’re starting something that will take over. I’m a nature bug."

Wright said he sees the program as a long-range management practice that can at least slow the spread of knapweed.

"This is a form of control, a nonchemical approach using insects that are natural predators to knapweed," Wright said.

The Gooding, Blaine and Elmore bug crews are newly established arms of the Southern Idaho Regional Bio-Control Project group. The groups will work this summer on the biological control of purple loosestrife, spotted and diffuse knapweed, leafy spurge and Dalmation toadflax in cooperation with the Tri-County, Wood River, South Fork of the Boise River and Camas Creek cooperative weed management areas.

They join the Camas Bug Crew, a five-year veteran of bio-control in Camas County.

 

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