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Fatal attraction: companion planting technique controls wireworms in potatoes

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Media Relations
Agriculture and Agri-Food Canada
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With spring comes planting season, and with planting season come unwanted guests for more and more Canadian farmers: wireworms. Decades ago these troublesome pests were successfully controlled with chlorinated hydrocarbon insecticides, but these agents were banned in the 1970s and 1980s because they were toxic to animals such as peregrine falcons and bald eagles. They also had a tendency to build up in the soil and, ultimately, in the food chain.

A sustainable and cost-effective solution is within reach thanks to Dr. Bob Vernon, a Research Scientist at the Agassiz Research and Development Centre, and his team. They have developed a new "attract and kill" method using tiny amounts of insecticide to decimate wireworm populations and limit damage to potatoes in the field. The technique can be implemented at low cost with minor modifications to planting equipment.

"With my method, you only need 5 grams of active ingredient per hectare. This new approach is superior not only in terms of reducing risks to the environment and to people, it also kills far more wireworms."

- Dr. Bob Vernon, Research Scientist, Agriculture and Agri-Food Canada

Wheat seeds treated with an insecticide act as bait and are planted along with the potatoes. The wheat germinates first in the soil, after about 48 hours. During germination, the wheat produces carbon dioxide, which attracts the majority of the wireworms in the field to the planted potato rows. When they reach the wheat seed to feed, the hungry pests contact the insecticide and die. This takes care of approximately 80-90% of the wireworm population in a field within about 2 weeks after planting, and also protects the potatoes produced later in the summer.

The wheat is planted about 15 centimetres below the surface, which means there is little risk of contact with the vast majority of animal life in a field - except, of course, wireworms. Because so little insecticide is used, residue doesn't build up in the soil.

A number of new low risk insecticides and insecticide combinations are under development using this new "attract and kill" delivery method, and should be available to growers in the not-too-distant future.  Other research efforts are also ongoing at Agriculture and Agri-Food Canada to identify alternative methods to control wireworm populations.

Key facts

Photo gallery

Photo of two potatoes, one healthy, one damaged with black holes.
A healthy potato tuber (left) compared to one damaged (right). The tunnelling results from late summer feeding by wireworm larvae.
Close-up of a man's hand holding a single wireworm in some dirt.
Wireworms are small, but they are causing big problems for potato farmers across Canada.

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