Radiation may prove more potent than pesticide against pepper pest

You may not have heard of the pepper weevil, but it's said to have cost Ontario farmers $83 million in crop damage in 2016. Now, scientists hope a blast of cobalt gamma radiation will prove more potent – and less problematic – than pesticides in controlling the creature.

The researchers, from University of Guelph, will hatch pepper weevils in a lab and douse them with radiation from the isotope cobalt-60, produced at Ontario's Bruce Nuclear power plant on Lake Huron.

Cobalt-60

James Scongack, ‎Vice-President Corporate Affairs and Environment at Bruce Power, said the generating station produces the isotope for an Ottawa-based company that exports it for scientific and lab use.

"Cobalt-60 is used in sterilization of medical equipment and a range of other applications," he told CBC Kitchener-Waterloo.

The weevil experiment will use the isotope's gamma radiation for a different kind of sterilization, explained Cynthia Scott-Dupree, environmental science professor and the Bayer Crop Science chair in sustainable pest management at the University of Guelph.

"The [laboratory] insects are exposed to gamma radiation created by the Cobalt-60, and this results in sterilization of the insects," she explained. "We release the insects we sterilize into areas that are infested by wild pepper weevils that continue to be fertile."

When the sterile and wild insects mate, she explained, "the offspring aren't viable: in fact, they don't even hatch."

"The result is the pest population eventually drops and there is no problem to contend with."

Radiation versus pesticide

Ontario's energy minister, Glenn Thibeault, has described the experiment as an "innovative, environmentally-friendly way to deal with agricultural pests that cause real harm to food crops."

Scott-Dupree said controlling this particular pest with insecticides has proven difficult because much of the creature's developmental life takes place inside the pepper itself.

Farmers can't get at the resident weevils with applied chemicals, she said, because the bug burrows into the skin of a pepper and its offspring develop and feed inside the protective casing of the pepper.

Scott-Dupree admits people are concerned about the idea of radiation harming other insects in the environment, but she said the insects are exposed to radiation "in very contained spaces" and that "once they are irradiated they don't pass the radiation on when we release them."

"They aren't emitting any radiation wherever they go." 

The technology has been used successfully since the 1950s on moths in British Columbia's apple-growing region, she said.

"Because it's so targeted, it doesn't have an impact on pollinators or any other beneficial insects," she said. 

Crop outlook

According to numbers provided by the university and Bruce Power, $83 million dollars worth of Ontario peppers were damaged by the weevil last year. The figure does not include the related costs of pest control or management.

The next stages in the experiment will involve hatching weevils in captivity and then testing to determine the optimum radiation dosage so that the insects are still able to fly and find mates but will not be able to produce offspring.

"We're very, very excited about this," Scott-Dupree said, "because it fits well with sustainable pest management ... and will certainly benefit growers in the province that are dealing with this very devastating insect pest."