Phylloxera disease and what it means to Colorado’s vineyards

Adapted from a Bookcliff Vineyard email…..

I thought you may want to know. Many of you asked me about phylloxera in Colorado’s vineyards, as you heard the news on television and on the radio. I thought I give you some more detail so you hear it from the horse’s mouth what phylloxera means for the Colorado grape industry and Bookcliff Vineyards.

For a grape grower to hear the word phylloxera is like receiving a death sentence.
What is phylloxera and why is there a deathly fear in the farming community? Phylloxera is a root louse, so tiny that it is only visible under the microscope. This tiny animal feeds on the roots and leaves of the vine, causing deformation of the roots that prevent water and nutrients being taken up by the roots. The progression of the disease is similar to cancer, most of the time the symptoms are detected late, several years after the infection, when the disease has reached stage II or stage III leaving only one alternative to remove and burn all vines. Early symptoms are similar to many other possible issues in the vineyard, such as iron deficiency, high salt content in the soil or lack of water.
Phylloxera is common in almost all grape growing regions in the world. There is no cure and no spray to control phylloxera, except for planting grafted rootstock rather than self-rooted vines. In Colorado we have had the luxury of planting self-rooted vines, meaning that the roots and the trunk are from the same species, for example Merlot. With grafted vines, the root stock is a particular clone of American native grapes and the actual plant is vinifera, such as Chardonnay or Merlot.
There are no nurseries in Colorado that raise vines. The rootstock planted in Colorado comes from nurseries in other grape growing region, that all have phylloxera. One possible source is the rootstock brought in to Colorado, especially rootstock of hybrid grapes raised in nurseries on the East coast of the United States. American hybrid grapes are resistant to phylloxera and can live with the root louse without any damage. With an increase in planting hybrid grapes, that are more frost and freeze resistant, since we experienced high damage in 2013 and 2014 in Colorado vineyards, the probability increases that phylloxera will be brought to Colorado. This root louse also can travel on people’s boots as they walk through the vineyard or get transported on our farming equipment, such as tractors, mowers and sprayers.
What does the arrival of phylloxera in Colorado mean? We all need to be vigilant. When buying rootstock we need to dip the roots in hot water before planting. We need to vet the nursery before buying rootstock. We cannot share equipment among farmers, unless we have a strict protocol of sanitizing the equipment. When walking into a vineyard, we need to sanitize the boots. We need to test the roots randomly for phylloxera and when detecting the presence take actions to remove and burn the plants. And we need to experiment with planting grafted vines. So far there was no need to figure out which rootstock will work in alkaline soil and an arid climate as Colorado. California soil is high in acid, for example.
But there is also the good news. We do not have the winged version of the louse in Colorado, which spreads much faster than the crawling version. The crawlers do not like sandy soil, which we have in Colorado, but prefer clay to crawl in the soil cracks to go from plant to plant. And we have much colder winters than other grape growing regions making it more difficult for the louse to survive the winter. Hopefully this means that the spread of phylloxera is slow and can be controlled in Colorado. Even better news. At Bookcliff we tested randomly roots from 40 different vines in different vineyards and all tested negative for phylloxera. Most of our vineyards have sandy soil except the Hawkridge vineyard. So when we plant some more acreage this spring we decided to plant 50% grafted vines and 50% self-rooted as a measure of insurance.
The arrival of phylloxera in Colorado created some additional challenges for grape growers in Colorado. But, between climate, soil, the research at the Western Research Station and precaution from the farmer we hopefully can keep the problem under control.

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