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Tiny wasps may help B.C. growers battle wine grape pest

The Virginia creeper leafhopper, Erythroneura ziczac, is a pest with a taste for British Columbia wine grapes. But trying to stop its feeding on local vineyards has presented a major dilemma for growers – how to control the pest without losing the industry’s worldwide reputation for low insecticide use.

Now researchers may have part of the answer – a tiny, harmless, parasitic wasp known as Anagrus daanei.

“This wasp is not something you’d normally notice in a vineyard – it’s very small and is just one of many species,” says Dr. Tom Lowery of Agriculture and Agri-Food Canada in Summerland, B.C. “But this species has an important difference – it develops within the eggs of the Virginia creeper leafhopper.”

That characteristic opens the door to using the wasp as a tool for biocontrol, he says. It’s just one of several options researchers are investigating as part of a new, grower-supported integrated pest management program for grape production, headquartered at Summerland.

The goal of integrated pest management is to develop sustainable strategies for pest control, based on better knowledge and a combination of tools, says Lowery. The new program is supported in part by the B.C. Wine Institute, which represents all wine grape growers in the province.

“Our B.C. grape growers use less insecticide than any other grape production area in the world,” he says. “We have a great opportunity to improve that even further with integrated pest management.”

On average, the province’s grape growers use less than one application of insecticide per year, and 80 percent of this effort is targeted at the Virginia creeper leafhopper, the number one pest of B.C. grapes.

The beneficial wasp would provide a tailor-made option for controlling this pest, says Lowery. He has mass-released the wasps in field trials in each of the past two seasons, with positive results. Future options include rearing the wasps for controlled releases in production areas, or pursuing other strategies that favor a build-up of the wasp population. “We’re looking into a few possibilities. But the bottom line is there’s great potential for this wasp to help keep the leafhopper population in check.”

In the course of the research, Lowery and colleagues discovered a second species of grape pest – the western grape leafhopper, Erythroneura elegantula. Although this pest is currently found only in a limited area of the province, it is more resistant to currently registered insecticides. A second wasp species, Anagrus erythroneurae, shows potential as a biocontrol against this newly-identified leafhopper.

“Things are more complicated than we initially thought, because we now have this second species of leafhopper,” says Lowery. “So we’ve been doing a lot of work to expand our program.”

In addition to research on the parasitic wasps, the researchers are looking into ways to improve the efficiency of insecticide use. “The first thing we have to do is get out there and find out more about the pest we’re dealing with,” he says. A strong foundation of science-based knowledge is essential to know when control makes sense and how to apply it most effectively with minimal non-target impact.

For example, the best time to spray for leafhoppers is early in the crop year, when the pests are less noticeable. “Later in the season, leafhopper adults and the damage they cause are very obvious – pickers hate them because they often end up inhaling some when numbers are high. But that’s actually not the best time to spray – the adult leafhoppers are much less susceptible to insecticides at this time than they are during the immature stages.”

Knowing when pest populations require control involves careful monitoring, he says. For leafhoppers, research also involves the development of temperature-based developmental models that can be used with the temperatures recorded in individual vineyards. “These monitoring tools will give growers a very good idea of the insects’ developmental stages and when control will be the most successful,” says Lowery.

Once the thresholds and timing for control have been established, the next step is selecting the best insecticides, he says. Researchers at Summerland are testing several products. “We’re looking not only at the effectiveness of individual products, but also at their impact on beneficial insects and other non-target organisms.”

Funding for the development of an integrated pest management program of insect and mite pests of grapes in B.C. is provided by the B.C. Wine Institute, the Investment Agriculture Foundation and the Industrial Research Assistance Program. The integrated pest management program is part of Agriculture and Agri-Food Canada’s mandate to promote innovation for growth, maintain security of the food system and protect the health of the environment.

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