Phylloxera, the Other Infection

It was a month before harvest. We were told that our grape order with a Walla Walla vineyard could not be fulfilled due to a light crop this year. Thinking that the unseasonably warm weather might be the cause, we switched our order and went with a Yakima vineyard instead. Then through the grapevine (no pun intended), I learned about the real culprit - phylloxera!

Cartoon from Punch, September 6, 1890

Phylloxera Plague

You may have heard of the phylloxera epidemic in Europe back in the 19th century. The vineyards there were severely decimated, bringing the wine industry to its knee. It started when American vines were brought across the Atlantic Ocean to be studied. Unfortunately, little pesky stowaways went along with them and somehow snuck into the vineyards.

Phylloxerae are microscopic insects that feed on the leaves and roots of the grapevines. In the roots, they can cause critical damage and introduce a secondary bacterial or fungal infection, eventually starving the vines of nutrients and water. It was estimated that over 40% of the French vineyards were devastated over 15 years during the plague.

Champagne vineyards once devastated by phylloxera

Early attempts to contain the plague ranged from chemicals to pesticides. Some vineyards even introduced predators like toads and chicken to control the phylloxera population. These attempts were in vain. The only viable solution was to graft European vines onto phylloxera-resistant American rootstocks. These rootstocks have developed a natural defense against the insect. When bitten, the American root exudes a sap to clog the louse's mouth and then forms a layer of tissue to protect itself from any secondary infection. 

The grafting approach was wildly successful in saving the European grapevines, also known as Vitis vinifera. You can thank the American rootstock as you sip your glass of Bordeaux or Barolo.

Dodging the Phylloxera Bullet?

Many vineyards growing Vitis vinifera grapes have preemptively avoided the threat of phylloxera by planting only vines that are grafted on resistant rootstocks. But there are areas in Europe and beyond that have remained unscathed by the louse. Apparently, phylloxera does not survive well in the slate soil of Mosel or the volcanic soil of Mount Etna. Grapevines in those areas are still grown in their native rootstocks.

Phylloxera also tends not to thrive in cooler climate. Until recently, Washington had been virtually phylloxera-free and was able to grow Vitis vinifera in their native rootstocks as well. However, with climate change, phylloxera has started making inroads into a few Walla Walla vineyards leading to an outbreak in 2019. 

Phylloxera does not tolerate cold winter

Reluctant to give up the native rootstocks, many Walla Walla vineyards hope to contain the spread of phylloxera through better sanitation practices and extensive quarantine protocol. Several vineyards have required boots to be disinfected and also placed a limit on visitor traffic. If nothing else, this may slow the spread and buy the vineyards time to plan for the eventual transition to American rootstocks.

While there is always the debate about the quality of wine being affected by grafted vines, the truth is that it hasn't hurt sales in Napa or Bourgogne. However, ripping off infected vines and replanting with new ones is very costly. Additionally, it often takes about three years before a new vine can produce viable grapes. 

One wonders how that all may play into the psyche of Walla Walla wineries as they deal with phylloxera. Are they going to be doers or deniers?