Spring 2001

On the Tail of the Sharpshooter
What a Small Brown Insect Can Teach California's Vineyard Owners

by Jennie Rothenberg

Last June, in Tulare County, California, swimming pools were covered, pets were brought inside, and 229 residences were sprayed with an insecticide called carbaryl. The chemical was one step in a statewide program to eradicate the glassy-winged sharpshooter, a small brown insect dreaded by the state's $33 billion wine industry.

The sharpshooter, which entered California 10 years ago, is a particularly swift carrier of Xylella fastidiosa, the bacterium behind vine ailment called Pierce's Disease. Though exact figures vary, newspaper headlines say the disease has recently reduced acres of Southern California vineyard land to rows of shriveled vine skeletons.

In response, more than $36 million in state and federal funding has been set aside to research the disease and combat the insect. "This pest could devastate California's grape and wine industry," Vice-President Gore told Bay Area residents last July. "If we don't step up eradication and control efforts, we could see substantial losses in the future."

The glassy-winged sharpshooter has not yet made its presence felt in Northern California. But when one was sighted in a Healdsburg nursery last September, Sonoma County residents called a public meeting to discuss what the future might bring. Agricultural Commissioner John Westoby raised the possibility of bringing carbaryl to Sonoma neighborhoods. Such spraying is not yet necessary, Westoby said. But if an infestation were to hit Sonoma, Westoby said the current prevention-based approach would not be enough to combat the insect.

This news did not sit well with locals like Maxina Ventura. A mother of two, Ventura moved her family out of Sonoma County once she connected their health problems with a neighboring vineyard's pesticide use. "Within ten minutes of the sprayings, my kids would start scratching themselves raw," Ventura said. "As a result, they'd get terrible staph infections." Ventura took these problems to Will Sumner, a toxicologist with Scientific Certification Systems in Oakland. Sumner linked this and other problems to carbaryl.

A Class III pesticide, carbaryl is billed as relatively low-risk. Laboratory tests so far have not found carbaryl to cause a significant increase in cancer or birth defects, and this has earned the chemical its mild reputation. But testing is still in its early stages. And meanwhile, the substance has been linked to a range of other health problems. A report from the U.S. Department of Agriculture's Forest Services lists blurred vision, muscle tremors, difficult breathing, and convulsions among the chemical's reported effects.

Few are claiming that carbaryl is entirely innocuous. "We wouldn't characterize any chemical poison as 'safe,'" said Robert Wynn, the California Department of Foods and Agriculture official overseeing the sharpshooter project. "That would be a contradiction in terms." Wynn said his goal is to develop chemical-free methods like breeding insect predators. "I have small children myself," he said. "I'd prefer not using any pesticides at all. But for now, they're a tool in our toolbox. They will continue to be part of our program."

The question is whether pesticides are even an effective short-term solution. Beth Grafton-Cardwell, a UC scientist who oversaw the Tulare project, says that carbaryl is toxic not only to the sharpshooter but also to its natural enemies. Moreover, while most young sharpshooters in Tulare were killed, many adults crawled down from treetops two days later. "We can't eradicate this pest," she said. "At best we can suppress it for a while and give the researchers some time."

With the best minds in the state working on the problem, it's surprising that more effective solutions have not been found. Greg Willis, founder of the Napa company Agri-Synthesis, says there's a simple reason for this."They haven't looked at all the alternatives," he said. Willis' company employs non-toxic techniques to combat vine diseases. "The issue is not the insect, it's the disease itself," he said. "We've developed specific formulas that give the vine and soil what they need to fend off the attack."

Willis has drawn public praise from large vineyards like Wente and Topolos for his success with insect-related diseases. He has developed an 18-month program to eradicate Pierce's Disease and is eager to share it with state officials. "I went to the Department of Foods and Agriculture and offered to tell them my solutions," he said. "Have I received a call back from them? So far, no."

One reason officials may be wary of Willis' approach is that scientists say Pierce's Disease has nothing to do with vineyard health. They hold that healthy plants are actually more susceptible to Pierce's Disease because they move bacteria more rapidly through their systems.

Farmer Bob Cannard, one of the leading suppliers of the acclaimed Berkeley restaurant Chez Panisse, says this shows an incomplete understanding of health. "In a garden, a 'healthy plant,' by definition, is one that's able to withstand disease," he said. "But in a UC lab, a 'healthy plant' is measured by yield and size. What you end up with are fat plants pumped full of water and nitrogen. They're diluted and unable to defend themselves."

Cannard applauds the solutions proposed by Willis and others, and says he is not worried about Pierce's in his own vineyard. But he says statewide change will only come if locals like Maxina Ventura make their concerns heard. "It's in everybody's best interests," he said. "Until now, science hasn't been looking at ways to increase life in a vineyard, only how to kill things. But if you stand up, they'll start to look for other ways to solve the problem. And that will be the best thing for the vines, the people, and all agriculture to come."