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Weevil to help cattle producers battle noxious weed hound’s-tongue

Help is on the way for Western cattle ranchers unarmed in their fight against the noxious weed hound’s-tongue.

A new industry-supported project led by Agriculture and Agri-Food Canada’s Lethbridge Research Centre will rear tens-to-hundreds-of-thousands of a European root-feeding weevil that targets and kills the weed, says biocontrol researcher Dr. Rose De Clerck-Floate. Researchers will then distribute the weevils to ranchers and land managers in interior British Columbia, where hound’s-tongue has become a serious problem of cattle production and a blight on rangeland.

“Hound’s-tongue is a foreign weed that has become widespread because of a lack of natural enemies,” says De Clerck-Floate. “The weevil originates on hound’s-tongue in Europe and will allow ranchers and land managers to control their own weeds in an economically feasible way. Already, the project is generating a lot of excitement within the ranching community – the weevil has started to become available in the past two years, and there’s a bottleneck in demand as more ranchers hear about its success.”

Hound’s-tongue is a colonizer of disturbed areas, says De Clerck-Floate. It often infests abandoned cropland, and forest sites cleared for cattle grazing, mining operations and road construction. Hound’s-tongue hinders forage establishment, which affects both cattle and wildlife, and has potential to poison the animals. Its burrs also irritate cattle and reduce their market value. B.C. cattlemen rank hound’s-tongue second only to knapweed as a priority for control.

The European root-feeding weevil was first released to target the weed at B.C. research sites in 1997, and is likely the best way to control hound’s tongue, says De Clerck-Floate. “The weevil has been very effective. On experimental sites where the release rate has been 200 to 400 insects, the weevils controlled the weed within two years. It has also been encouraging to see that the weevils seek new patches of hound’s-tongue.”

Chemical control is another option, but one that is impractical and costly on rangeland. “This is a sneaky weed that will grow under canopy, which makes it hard for ranchers and weed managers to find and selectively kill the plants,” she explains.

The need for a cost-effective way to mass-rear the weevils is what prompted the new project and propelled its strong support from industry, says De Clerck-Floate. “Insectories and specialized laboratories are standard sites for mass-producing beneficial insects, but these require costly overhead and expertise. The approach we decided upon is potentially far less costly, and is truly novel in the field of weed biocontrol.”

As a first step, researchers will farm hound’s-tongue as a row crop in select areas, she says. Then they’ll seed the insects into the weed and harvest the offspring. “Proper steps will be taken to prevent the weed crop from spreading, and it will be grown specifically in areas where hound’s-tongue is already a problem, so any insects that move beyond the row crop will be welcome.” In addition to work at the Lethbridge Research Centre, researchers are conducting the project on private rancher and farmer properties, at their request, in Creston Valley, B.C. The weevils produced from the project in Creston will be ready for distribution to the various partner groups first in 2004 and also in 2005.

Eventually, the project may evolve to the point where ranchers and land managers can cost-effectively produce their own weevils, says De Clerck-Floate. “As part of the initial phase of this project, we’ll examine the best strategies for rearing the weevils, looking at variables such as fertilization and row spacing that ultimately result in more, bigger and healthier weevils. This will improve future rearing efforts.”

With promotional help from the Boundary Weed Management Committee of British Columbia, the project obtained one year of funding from the Cattle Industry Development Council of B.C., the Kettle River Stockman’s Association, and the Southern Interior Stockman’s Association. De Clerck-Floate hopes to continue the project for another three years and will be looking at bringing more groups on board for funding support.

The Boundary Weed Management Committee and interested ranchers have provided hound’s-tongue seed for planting. The B.C. Ministry of Forests will provide some of the needed ‘seed’ insects from their insect propagation facilities in Kamloops, and the remaining insects to be seeded into the weed crop in June 2003 will be produced at the Lethbridge laboratory this winter.

Biocontrol research at Agriculture and Agri-Food Canada’s Lethbridge Research Centre illustrates the government's commitment to promote innovation for growth, maintain security of the food system and protect the health of the environment, as proposed in the new Agriculture Policy Framework. The framework aims to increase profitability for producers by giving them the tools and capabilities to respond to constantly changing consumer demands for safe food produced in an environmentally responsible way.

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