Agriculture: Trouble At the Roots

In Napa and Sonoma counties, heartland of California's $730 million-a-year wine industry, prospects are promising for a bumper harvest this fall. Beneath the deceptively lush surface of the peaceful vineyards, however, an expensive disaster looms. Billions of microscopic parasites called phylloxeras are munching away at the roots of the grape-bearing stalks. While no threat to human health, within a decade the tiny insects could eat their way through 50,000 acres of the nation's finest vineyards. Estimates of the total damage, including the cost of replanting with Phylloxera-resistant stalks, range from $500 million to more than $1 billion.

That is the bad news. The good news is that the crisis will force growers to replace their diseased vines with new, better quality grapes that can flourish in the region's wide range of microclimates, which feature coastal fog as well as baking heat. Some unprofitable and marginally successful varietals will probably disappear, at least in Napa and Sonoma. But vintners insist that they will soon be able to produce more of the premier wines consumers want -- notably Chardonnay and Cabernet Sauvignon.

This is not the first time grape growers have fought this burrowing louse, which is indigenous to North America east of the Rockies. In the late 19th century, phylloxeras somehow spread to vineyards in Europe and California, devastating more than 2.5 million acres in France alone. What finally brought the plague under control was the discovery that classic European varietals like Chardonnay could be successfully grafted onto native American rootstalks that resisted the voracious bug.

In rebuilding the American wine industry, growers tested a number of rootstalks. A majority settled on a variety called AXR 1 because it suited California's conditions so well, even though it was not totally immune to the phylloxeras. In 1979 a Napa County farmer noticed that his vines were thinning out and called in experts from the department of oenology at the University of California at Davis. They concluded that the phylloxeras had mutated into a new, prolific biotype that threatened all AXR 1 rootstalks. Reproducing asexually, one insect can spawn a billion offspring annually.

In California as well as in Washington and Oregon, where phylloxeras have also been spotted, the lice feed on roots as deep as 6 ft. beneath the soil, leaving them susceptible to soil fungus and other infections. Roots under attack become swollen and deformed; eventually the vine and its grapes shrivel and die. Says Ed Weber, a Napa County viticultural adviser: "It looks like someone took a blowtorch to them."

The University of California has set up a Phylloxera Task Force, but no chemical treatment has proved effective against this new biotype, and experts cannot rule out further mutations. In fact, another strain of the louse has been found in central California and as far south as Santa Barbara. For farmers the safest solution is to rip out their AXR 1 and replant with one of a dozen or so other rootstalks that appear to be more resistant to the mutations, at least so far. After replanting, it takes three years for a vine to produce mature, harvestable grapes.