Phylloxera, history's most infamous winegrowing scourge, has reared its ugly head in an emerging American wine region. Researchers at the U.S. Department of Agriculture's Agricultural Research Service confirmed the presence of phylloxera in a Mesa County, Colorado, vineyard on Nov. 29. Over the next month, the insect was found in three more locations, all within the Grand Valley AVA, one of Colorado's two appellations, which runs along the Colorado river and surrounds the towns of Palisade and Grand Junction.
According to Dr. Horst Caspari, Colorado State viticulturist and a professor of viticulture at Colorado State University's Western Colorado Research Center, further investigations will have to wait until frozen vineyard ground thaws in the spring.
Phylloxera is an insect in the aphid family that feeds on vine roots, damaging the plant by disrupting water and nutrient flow. Vines appear weakened and stunted at first, and die within a few years as host to the parasite. Native to the east coast of the United States, phylloxera nearly wiped out viticulture in France during the mid-19th century when it was accidentally imported. Eventually a solution was found: Growers grafted Vitis vinifera vines onto rootstocks of American vine varieties that are phylloxera resistant.
The aphid has since spread to wine regions throughout the world, but some regions remain phylloxera-free. Until November, surveys had found no evidence of phylloxera in Colorado's commercial vineyards.
Colorado is no newcomer to winemaking. In 1890, a former Colorado governor planted a 60-acre vineyard in the Grand Valley region, and by 1910 the region had more than 1,000 growers. Colorado's modern wine industry got its start, however, in the 1970s, and today the region boasts about 1,000 acres planted to vines, with 129 wineries producing 166,000 cases of wine annually. Sales totaled more than $33 million in the 2016 fiscal year.
Asked where the phylloxera came from, Caspari said, "We're fairly certain that we are dealing with multiple introductions from different sources." He pointed out that the region has been heavily replanted over the past few years because of cold damage. "We've brought in quite a lot of plant material from all over. Colorado has no vine nurseries of its own, so all plant materials come from out-of-state nurseries."
For the time being, growers are being advised to watch for yellowed leaves, stunted growth and other symptoms that mimic nutritional deficiencies. They're also being advised to thoroughly clean all harvesting and cultivating equipment and to request that all new nursery stock be treated before shipping.
As for costs to the industry in terms of money and labor, Caspari said it would be, "insignificant at this point in time. The biggest cost would be related to the removal of infested vines, and that's not much. More significant to the grower will be the loss of revenue in future years. Of course, that could all change if more as more acres get infested in the future."