Pests Bug Northwest Vintners

Cracked berries draw fruit flies in Oregon, while wasps cause trouble at B.C. crush site

by Peter Mitham
stag's hollow winery
Wasps swarm a cluster of Dolcetto at Stag's Hollow Winery near Okanagan Falls, B.C. Owner Larry Gerelus says the pests tend to focus on one cluster and leave the rest untouched. Source: Larry Gerelus/Stag's Hollow Winery

Corvallis, Ore./Okanagan Falls, B.C.—Stink bugs, fruit flies and wasps are infesting vineyards across the Northwest, and while wine quality may not be affected, the bugs are proving the proverbial fly in the ointment.

The good weather that’s delivered growers a near-ideal year and promised winemakers a top-quality vintage has also boosted insect populations.

“The pest pressure is definitely higher than it’s been in previous years,” said Vaughn Walton, an entomologist with the Oregon Wine Research Institute at Oregon State University.

Species on the rise
On the road between vineyard visits, Walton told Wines & Vines that a mild winter, ambient spring, and warm summer temperatures had created ideal conditions for fruit flies including spotted wing drosophila (D. suzukii) and brown marmorated stink bug (identified in some vineyards last year) to reproduce (see “Asian Fly Detected in Northwest Vineyards” and “Oregon Winemakers Raise Stink about Bug”).

“You’re seeing a lot more of those around because of the ideal summer temperatures,” Walton said. “If we’re looking at spotted wing, this is the worst year on record so far, and I think the same would apply to Drosophila melanogaster (the common fruit fly).”

Willamette Valley growers have been seeing a particular abundance of fruit flies this year, thanks primarily to recent rains that caused berries to swell and crack. This created opportunities for D. melanogaster, which typically infests damaged fruit. D. suzukii is feared because it preys on ripe fruit (a saw-like ovipositor allows it to cut the skin to deposit eggs, rather than relying on injuries), but it typically prefers thin-skinned produce and has proved to be more troublesome in berries and cherries than wine grapes.

Cracked fruit have given D. suzukii an opportunity alongside D. melanogaster.

“We’re finding that the majority of the flies that are emerging from the berries are Drosophila melanogaster, which is the fly that we generally find in wine grapes,” Walton said. “However, when you go and look at the berries themselves, you see a mix of the two species.”

With respect to brown-marmorated stink bugs (reported in Hood River last year and also in Southern Oregon, and now appearing in California, too), Walton said there are no reports of economic damage from the invasive species in vineyards.

“The biggest concern is for hazelnuts; they seem to really prefer those,” Walton said, noting that this may change as bugs begin to prepare for the winter. “We’re just making sure that growers are aware of the problem if it starts becoming worse.”

Wasps in B.C.
Further north, in British Columbia, the topic of the day has been wasps.

A surge in populations through the province’s southern interior has prompted many vineyards to hang wasp traps aimed at reducing hazards for harvesters and damage to grapes.

Larry Gerelus of Stag’s Hollow Winery near Okanagan Falls noted that while the boom in wasp population is the biggest he’s seen in 17 years, it isn’t a full-fledged plague.

“It looks worse than it really is. They are doing damage, but they tend to gather around one cluster, and then there will be clusters next to them that are perfectly clean,” he said. “Birds are far, far more difficult to deal with—and far more destructive very quickly.”

Similarly, Kirk Seggie, vice president of operations for Andrew Peller Ltd.’s vineyards in British Columbia, said bunch rot has been the biggest issue thanks to a wave of rain after Labor Day.

“Wasps don’t seem to be that bad in the vineyard,” he said, while noting that the sweet-toothed stinging critters made conditions “a little dicey at the crush site” last week.

Quality control
Andrew Peller’s vineyard managers and growers have been paying closer attention to controlling bunch rot.

“Once you’ve got it, you’ve got it, so you’ve got to cut it out before you harvest,” he said.

This means workers are passing through vineyards, cutting out spoiled clusters prior to harvest. Grapes are then harvested and promptly processed to avoid degradation of the fruit.

The varieties hardest hit have been Pinot Noir, Pinot Auxerrois and Sauvignon Blanc, which have thin skins and tight clusters.

The dedication prior to harvest promises a good vintage, or as Walton noted: “I don’t think that the crop quality will be affected, because I know that growers take every possible precaution to ensure that substandard grapes are not harvested or put into winemaking.”

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