Wine Openers

One of the terms tossed about during last week’s discussion of the discovery of phylloxera in Colorado vineyards was “symptomless carrier.” Which means (in this case) a grape vine may have phylloxera (which is the tiny bug that kills vines by attacking their roots) but shows no sign of the infestation.

Phylloxera aphids on a vine root. Photo – Australia Department of Food and Agriculture

I know, that’s not the preferred medical definition but give it up, these guys are grape growers, not doctors. Except, that is, for one or two, who offered this definition – A symptom is something only you know is there. A sign is something other people can notice.

Whether you use symptom or sign, the concern is the same: you might have an aphid-infested grape vine and not know it until it and its neighbors start to wither.

And with phylloxera, that physical manifestation is just the tip of the aphid iceberg because by then the bugs have spread.

First the worst news: “The rule of thumb is, once you find phylloxera, the vineyard is doomed,” intoned Bob Hammon, entomologist at the CSU Extension Service, during the packed-house phylloxera seminar Monday at the 2017 VinCo Conference.

And as of this writing there have been four vineyards in the Grand Valley positively identified to be phylloxera positive. Only one has been publicized.

“There’s no doubt in my mind it’s far more widespread,” Hammon said.

The bug will kill (most of) your vines but not all at once, Hammon and other experts warned.

It may take the phylloxera aphid a decade to move through your vines, which gives the grower time to save his livelihood, if not those specific vines.

While there are exceptions to every case, phylloxera kills vinifera vines, not the native American grapes that developed alongside the bug and have some resistance.

There are some sites in Europe (and here), which first noticed phylloxera in the 1860s after American grapevine cuttings spread it there, that haven’t been affected in the 150 or so years the rest of that continent has been tearing up and replanting vineyards.

Getting rid of own-rooted vines, especially vinifera vines, and using grafted rootstock is one and probably the surest way to combat phylloxera.

It’s expensive, adding about $2.50 to the cost of a vine. Plus, you could leave the vineyard fallow for a year and then wait another 3 years for a crop.

And you still must be careful about not spreading the bug around by carrying infected soil on your boots or tractors or other machines.

Also, grafted rootstock need protection against the harsh winters we get in Western Colorado.

Those aphid-resistant American grapes? Most of them don’t make good wines, or at least not wines demanded by most consumers.

Using vinifera vines grafted to resistant rootstock allows growers to produce the grapes winemakers want.

“No region has even succeeded in keeping it from spreading,” said Nancy Janes of Whitewater Hill Vineyards and Winery. “You can slow it down a lot but nobody has succeeded in stopping it.”

It comes down to managing the bug once it appears.

If you’re a big grower like Bruce Talbott, whose company manages upwards of 40 vineyards across the valley and consults on another 20 or so, your decision is rooted in economics.

If a phylloxera is found in their vineyards, “our response probably will be we assume everything we farm has got phylloxera and we will spray it with Movento,” a systemic insecticide against sucking pests, Talbott told the VinCo seminar.

“If it costs $100 an acres, it costs us $100 an acre,” he said. “That’s a lot cheaper than the other things.”

If you’re smaller, it’s still economics. Is it cheaper to pull your vines, wait and then re-plant or do you go into another crop, like peaches?

“Unless we get Napa-like prices, grapes will never replace peaches as a cash crop,” offered Talbott. But growing grapes allows him the latitude of keeping his Mexico-based crews working for six months or more.

For small-acreage growers, “the better approach is if it’s in here now, I better work at replacing a third or quarter of my vineyard,” said state viticulturist Horst Caspari of the CSU Research Center. “That way I stay in the production and not go (without a crop) for two or three years.”

VinCo, the annual Colorado wine-industry tradeshow and conference sponsored by the Colorado Association for Viticulture and Enology (CAVE), kicks off Monday (Jan. 16) and of certain interest will be the discovery of Phylloxera in commercial vineyards in Colorado.

The bumps on the underside of this grape leaf are caused by Phylloxera. A strain of the insect that attacks the roots of vines is found in Colorado. Photo courtesy Univ. Of Wisconsin-Madison

Phylloxera, as any good student of wine should know, is a microscopic aphid which, depending on the strain, feeds on the sap in grape vine leaves or roots. The aphid causes fungal infections as well as galls (see photo taken by researchers at the University of Wisconsin-Madison) to grow around the feeding site, blocking the flow of nutrients to the rest of the vine and potentially killing the vine.

Certain varieties of grapes, particularly the much-preferred European (Vitis vinifera) grapes, are extremely susceptive to Phylloxera while some native American grapes, which developed alongside Phylloxera, are tolerant or resistant. In the 1850s Phylloxera inadvertently was transmitted via infected grape vines to Europe and by the late 1860s the louse was making havoc of the European vineyards, especially in France.

It’s estimated that nearly three-quarters or more of Europe’s vineyards were stung by Phylloxera. Not until European growers learned to graft European vines to aphid-resistant American rootstock did Europe’s wine industry recover.

Phylloxera has been seen in wild Colorado grapes for years but not until in 2015 was it found in a commercial vineyard on the Front Range and then last November on the Western Slope.

“I’ve been concerned about it for quite some time,” said Bob Hammon, an extension agent with the Colorado State University Extension in Grand Junction. He said records of Phylloxera in Colorado go back at least a decade or more. “I figured it was going to catch up with us eventually.”

Because it was thought Colorado vineyards were Phylloxera free, grapevines here mostly are own-rooted, not grafted roots. The benefit is that should the vines freeze to the ground (which happened here in 2009, 2013 and 2014), the new growth will be true to the variety planted.

With a grafted root, if the upper part freezes, you don’t know what will sprout below the graft.

Grafting popular European grape varieties to American rootstock doesn’t get rid of the aphid but you get the grapes you want. Because Phylloxera is spread through the soil, one way to prevent spreading the aphid when importing vines is to hand-dip each vine in hot (125-degrees or so) water.

John Behr and Nancy Janes of Whitewater Hill Vineyards and Winery started hand-dipping several years ago when they began importing rootstock from Phylloxera areas in the eastern U.S.

“Back there, hand-dipping is an accepted practice,” Nancy Janes said. “When we’re getting grapes from known Phylloxera areas, we do it as standard practice.”

That includes parts of both California and Oregon, popular rootstock sources for Colorado’s grape growers.

Although other wine-producing areas have spent many years and even more dollars studying Phylloxera, research in using grafted rootstock is sparse in Colorado, said state viticulturist Horst Caspari.

“We haven’t had that necessity,” he said. “But the rest of the world uses grafted rootstock and we can build on that.”

Because Phylloxera kills slowly, Caspari said grape growers have time to adapt to new methods of vine management.

One current option calls for uprooting and burning infected vines and the field left fallow for a year before replanting grafted rootstock. But grapes need three years to produce a crop and that’s four years in all, “a long time to be without a paycheck,” noted Hammon.

Also, since Phylloxera can be spread on dirt-covered farm equipment, vehicles, and even vineyard clippings, management becomes more complex, said Hammon.

“We have to extra diligent about sanitation, paying attention to how you move equipment and people from field to field, it’s very challenging,” he said.

And wine-making already has its share of challenges, Nancy Janes noted.

“It’s absolutely heart-breaking knowing that it’s here,” she said.

The VinCo panel discussion on Phylloxera will be 1 p.m. to 5 p.m. Monday at Two Rivers Convention Center. Information at the CAVE website.