Four Colorado vineyards test positive for crop-damaging insect

GRAND JUNCTION, Colo. – Four vineyards in western Colorado have tested positive for an insect that has a history of causing widespread damage to wine grape crops.

Agriculture officials first identified the insect, known as grapevine phylloxera, at a Mesa County vineyard in November. Since then, three more vineyards in the county have tested positive for phylloxera.

The insect can take multiple forms and affect different part of the grape plant but the type discovered in Colorado feeds on the roots of Vitis vinifera grapevines. That lowers the plant’s ability to take in water and nutrients and eventually kills the vine.

Phylloxera is native to the eastern and southeastern United States, where grapevines evolved alongside the insect and are therefore resistant to the bug. It’s also been found in other wine-producing regions, including California and Europe, but until recently had not been found in Colorado.

Phylloxera wiped out two-thirds of all Vitis vinifera vineyards in Europe in the 1800s.

Officials recommend grape growers take a number of precautions to limit the spread of the damaging insect:

• Inspect all new nursery stock before planting.
• Request all nursery stock be dipped in hot water before shipping to kill phylloxera. If nurseries can’t hot water dip vines, growers should do it themselves.
• Power wash or sanitize all harvesting and cultivation equipment in between fields.
• Watch plants for symptoms, including yellowing leaves, stunted growth, poor vigor and other signs of malnutrition.
• Contact the Western Colorado Research Center at CSU or the Colorado Department of Agriculture for a survey of the vineyard.
• Consider switching to grapevines that are grafted to phylloxera-resistant rootstock.

Growers can contact the Colorado Department of Agriculture at 303-869-9070 for more information.

Winemaking is big business in Colorado. Officials say the state’s 140+ licensed commercial wineries produced 166,000 cases of wine in fiscal year 2016, which translated to more than $33 million in sales.