Wireworm populations appear to be on the rise in Western Canada.
Wireworm, which is the larval stage of the adult click beetle, affects many crops, including cereals and pulses, but they are particularly damaging to potatoes. Holes created by wireworms can render tubers unmarketable and serve as points of entry for potato pathogens.
This pest has remarkable staying power in fields due to its long life cycle — up to five years, longer than most producers’ rotations — and ability to thrive on so many hosts.
And it’s hard to pin down due to the sheer number of its species across Canada — around 30, each of which might behave differently.
Few chemical controls are available across Canada. Following the deregistration of lindane several years ago, many producers turned to neonicotinoid seed treatments. But neonics don’t kill wireworms, they just keep them from feeding on plants for a time, says John Gavlovski, Manitoba’s provincial entomologist, meaning they can return and feed on tubers later in the growing season.
And as neonicotinoids are under review with Canada’s Pest Management Regulatory Agency, this option might soon be taken off the table.
One option for control is Thimet 200G, an organophosphate systemic insecticide. But Thimet 200G is restricted, meaning producers who want to use it have to complete a certification and licensing requirement, says Vikram Bisht, Manitoba’s potato and horticultural crops pathologist. Manitoba producers have all but ceased using it, he says.
“The processing industry here is having increasing concerns about wireworm,” says Bisht.
Currently no large-scale monitoring projects are planned in Manitoba but Bisht says it’s on industry’s radar. “Unlike PEI, we don’t have those high populations, but it’s still a growing concern to many of our growers and the processing industry,” he says.
Gavlovski says a multi-year project out of Brandon University is set to begin in 2018 to measure the effectiveness of tests used for monitoring wireworm populations.
With the lack of available chemical controls, some Canadian potato growers are turning to innovative mechanical solutions.
Christine Noronha, an Agriculture and Agri-Food Canada researcher based in Charlottetown, PEI, says many eastern Canadian producers aren’t using any chemical controls for wireworm.
“I don’t know if it’s on the increase or not in Nova Scotia and New Brunswick, but more people are calling to ask what to do about it,” she says. “It creeps up on producers because the population increases exponentially, because the pest has a five-year life cycle. That’s what growers are seeing in Nova Scotia and New Brunswick. But it’s not at the levels we have here on the island.”
Noronha invented the Noronha Elaterid Light Trap (NELT), a pitfall trap that uses light to attract male and female click beetles. Originally designed as a monitoring tool, the trap can also be used for population control.
“In PEI we’re catching a lot of females using the trap,” says Noronha. “If you catch them early enough you take away egg-laying females. So over time you can reduce the load of females in fields. I’m trying to figure out a way that growers can use it because you cannot mass trap in fields.”
Last year the trap was commercialized by a company called Growing Forward Solutions on PEI. Producers anywhere in Canada can order their own. It hasn’t yet been tested on western Canadian click beetle species, but Noronha says she invites producers to collaborate with her on testing the trap.
“I’m more than willing to go out there, show it to them and put it out in their fields. They just have to call me,” she says.
Noronha recommends a four-point strategy for wireworm control:
- Monitoring for adults and larvae to get a sense of population levels;
- Using a good rotation before potatoes;
- Trapping every year regardless of crops planted; and,
- Using insecticide during potato years.