Native Plants Reduce Need For Vineyard Water, Pesticide Usage

Scientists in eastern Washington are finding drought-tolerant alternatives to roses at the end of vineyard rows that not only save on water, but increase predators of pests that are harmful to crops.

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Roses traditionally have served as not only beautification in vineyards, but were once used to detect the onset of diseases such as powdery mildew, which affects roses before grapevines. But those roses also require a lot of water, which isn’t in abundant supply in many parts of Washington.

The Washington State University Wine Science Center in Richland, WA, is experimenting with native plants — bitterbrush, purple sage, and rabbitbrush — that are used to the dry environment and don’t need additional water after getting established. In Washington, where many grape growers are using deficit irrigation, that’s especially important.

“No grower is going to water groundcover specifically, so we need something that is going to be drought-tolerant and survive,” says David James, an associate professor of entomology at Washington State University.

James says he’s seen increases in the predators, such as parasitic wasps, that feed on leafhoppers, spider mites, and cutworms, which can all be problems in vineyards. Those wasps and others are what he calls “generalists,” which mean that they will feed on many different pests that might be damaging grape crops from year to year.

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“We don’t have a single pest that dominates every year,” he says. “A lot of them are controlled or are helped to be controlled by a group of natural enemies.”

That means fewer pesticides, especially broad-spectrum pesticides that might also kill predator populations, have to be used in vineyards.

“They’re at a stage where they use relatively few pesticides and rely on native biological predators,” James says.

An additional benefit is that James says he’s seeing native butterflies, whose populations had been dwindling, in vineyards. Adding native plants gives those species, and others including some lizards, important sources of food or habitat.

“Some of these native plants are also hosts for caterpillars,” James says. “There’s a potential to create wildlife conservation area in vineyards as well.”

While the plant species James is using are specifically adapted to Washington, other regions or states could also determine the types of plants that would increase beneficial predators in their areas.

“The principle of what we’re doing can be applied in viticulture in the U.S., other countries, and in other crops as well. It would have to be tailored to that geographic region,” James says.

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