Sharpshooters Take Aim At Northern Californian Vines

Agriculture inspectors are the ever watchful guardians of the Northern California wine industry, worth $600 million, from a small but deadly adversary.

The glassy-winged sharpshooter is a sap sucking insect just over 1cm long. They are the main carrier of Pierce’s disease, an incurable condition caused by the bacterium, Xylella Fastidiosa, which starves an infected plant of water and nutrients.

Pierce’s disease affects vital economically important crops that grow in the warm climates of North and South America. It affects plants supplying as almonds, blueberries, citrus fruits, coffee, peaches, plums and yes you’ve guessed it, grapes.

Pierce’s disease has a history that is almost as old as the California’s wine industry.

In 1857 the Los Angeles Vineyard Society settled in the Santa Ana Valley. Within 25 years the area was producing over a million gallons of wine annually. Then in 1883 almost all of the vines inexplicably died. For ten years farmers tried unsuccessfully to rejuvenate the industry but to no avail. The Southern Californian wine industry effectively ceased for forty years, finally killed by the 18th Amendment (Prohibition) in 1919.

In 1889 the United States Department of Agriculture (USDA) dispatched Newton B. Pierce, to Santa Ana to determine the cause of the disaster. After extensive research he finally concluded in 1892 that the vines had been killed by an incurable microorganism.

It is only relatively recently that Pierce’s disease, as it came to be known, was more understood and recognised as a threat to vines. However, it took a major outbreak caused by glassy-wing sharpshooters in Temecula in 1999, to galvanise action.

Initially spread by the blue-green sharpshooter, Pierce’s disease is now far more effectively spread by the glassy-winged sharpshooter. Introduced accidentally to Southern California in 1989 through imported nursery stock from the southern U.S., the glassy-winged sharpshooter spreads Pierce’s disease with great speed. This insect is a voracious feeder and breeds quickly creating a multitude of offspring.

So great is the threat of the disease and the insects carrying it that the U.S. government has committed more than $60 million to try and defend California’s $3 billion wine industry. Worldwide there is a huge amount of research going into stopping this disease. Researchers in Sao Paolo, Brazil, have even mapped the genome of Xyella Fastidiosa.

This is not just an American problem. Southern Italy reported an outbreak of Pierce’s disease last year and now has more than a million infected olive trees. Vinis Vinifera, the European vine, has no immunity. Research into breeding resistant vines is ongoing.

Pierces disease is costing California over $100 million a year according to the Center for Wine Economics. Northern California, largely free of glassy-winged sharpshooters, is only able to remain so thanks to hard working agricultural inspectors and constant vigilance.

Image by Reyes Garcia III, USDA Agricultural Research Service [Public domain], via Wikimedia Commons.

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