Could a parasitic fly help solve P.E.I.'s growing Japanese beetle problem?

There could be a biological solution to P.E.I's growing Japanese beetle problem.

After years of work, researchers with Agriculture and Agri-Food Canada are zeroing in on a type of fly that can literally take a bite out of the pest that is wreaking havoc on gardens across the country.

Christine Noronha, a P.E.I.-based research scientist with Agriculture and Agri-Food Canada, said the winsome fly (Istocheta aldrichi) lays its eggs on the beetles. Once the eggs hatch, the fly larvae eat the beetles from the inside, usually before the beetles can themselves lay eggs.

Populations of the parasitoid fly have already been released in British Columbia and Ontario, which are also dealing with a Japanese beetle problem, and Noronha said it is doing its job there.

"It is keeping the population low," she said. "Biological controls never eliminate the population, but it is working."

Christine Noronha, an entomologist working with Agriculture and Agri-food Canada, is shown in a file photo. (Kevin Yarr/CBC)

The invasive Japanese beetle, or Popillia japonica, was first reported on the Island in 2009. Its population has been growing ever since.

The beetle likes the Island's warm, moist conditions and its lack of natural predators, said Noronha. It lays its eggs in grass and goes on to attack about 300 different plants, with a special affinity for roses, peaches and grapevines.

Right now, Noronha said the beetle is mostly a concern in people's gardens, but it could become an issue for farmers as the population spreads.

"They could become a problem in fields eventually if we don't do something," she said.

Japanese beetles like warm, moist conditions and are especially destructive to roses, peaches and grapevines. (Carolyn Ryan.CBC)

More research is needed before the parasitoid fly is introduced to Prince Edward Island, but Noronha said if everything goes well, that could happen next year.

In the meantime, there are some products Islanders can use to help deal with the problem.

Noronha said spraying your beds with beneficial nematodes — which are microscopic worms that occur naturally in soil —can help kill off beetle larva. The best time to do that is in the spring.

When the beetles reach adulthood, from about mid-July until mid-October, some gardeners suggest picking them off plants one by one and flicking them into a jar of hot, soapy water. You could also cover plants you want to protect with a light netting before you start to notice leaf damage.