Walla Walla Wineries Confront Phylloxera

The Washington wine region’s sandy soils were considered immune to the infamous pest, but it’s been hiding in plain sight

Walla Walla Wineries Confront Phylloxera
In advanced stages, the phylloxera louse can lay eggs in telltale galls on leaves and roots. This vine is not in Washington state, where some vineyards have a much less severe version. (istockphotos)
Sep 9, 2019

Winegrowers in the Walla Walla Valley appellation in southern Washington state, an AVA with the second-highest concentration of vineyards and wineries in the state, have made an unpleasant discovery: Some have found phylloxera, the vine-sucking louse that nearly wiped out the vineyards of Europe a century ago, attacking the roots of their vines.

No grower likes to find the pest, but in this case it’s particularly surprising. While phylloxera had been identified in some Washington vineyards more than 100 years ago, and a USDA scientist from Oregon even identified the pest in Walla Walla vineyards 20 years ago, the problem has always been minimal and not of major concern to Washington growers.

Washington state and, in particular, the Walla Walla Valley, have long been considered less-than-hospitable terrain for the phylloxera louse because of their sandy soils. So much so that, according to Washington State Wine Commission president Steve Warner, 99% of the state’s vines are own-rooted, meaning that instead of being planted on phylloxera-resistant North American rootstocks, the Washington vines have been planted on their own roots.

So what happened?

Apparently, phylloxera has been hiding in plain sight. According to Michelle Moyer, associate professor of entomology and statewide Washington State University (WSU) viticulture extension specialist, “Some vineyards in Walla Walla have had symptoms of decline for years but nobody thought that phylloxera was the cause. It was a slow decline, whereas people have always thought of phylloxera [infestation] as a rapid decline condition.

“During our summer planning sessions with growers in the area this year, the discussion turned to invasive pests with the consensus being that ‘We don’t talk about phylloxera enough.’ Growers then went back to their vineyards and started looking.”


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One grower in particular found what he was pretty sure was phylloxera and contacted the Washington State Department of Agriculture (WSDA), which positively identified the insect.

“The grower in question started reaching out to other growers in the area and they, too, started looking, and some of them did find phylloxera,” said Moyer. “They did a great job of talking with each other.” (Admitting that you’ve got phylloxera in your vineyard is like admitting you’ve got head lice. No one wants to talk about it, but something has to be done about it quickly.)

When asked why this problem has surfaced now, Andy Walker, the University of California’s grape and rootstock breeder, said “It’s everywhere. It always has been. It’s been there a long time but it’s never really taken over in a big way. Could be climate. Could be irrigation practices. Could be so many different things.”

What’s to be done?

According to Vicky Scharlau, executive director of Washington Winegrowers, the find “offers an opportunity for the industry to raise awareness for best practices” to prevent spreading of the pest. Phylloxera can travel in dirt that’s unwittingly carried from one vineyard to another. Measures such as using only certified clean stock, wearing rubber booties, restricting traffic to paved areas, not sharing equipment or trucks, loading and unloading trucks outside the vineyards, and making sure dirt is wiped off of feet and equipment when it leaves the vineyard can all help.

If there’s a bright side to all this, it’s that phylloxera is considered by many to be “manageable,” meaning that while at times, decline is rapid and definitive, with proper conditions and careful management, phylloxera-infested vineyards can last a long time. Christine Clair, vineyard manager at Willamette Valley Vineyards in Oregon’s Willamette Valley, pointed out that, “Three of our historic vineyards with phylloxera in them, identified over 20 years ago, are still producing high-quality fruit today.”

In the long run, “the only solution will be for [affected] Walla Walla growers to take out their vines and replant using phylloxera-resistant native American rootstock,” said Walker. Fortunately many of them will have the time to do so at leisure and extend the cost over a period of years rather than racing to replant all at once.

News Vineyard Pests Oregon Washington

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