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California Growers: What Damaged Our Vines?

Aerial spraying of pesticides may have drifted onto Lodi vines; extent of loss is yet to be determined

Lynn Alley
Posted: July 18, 2014

Some 200 grapegrowers in California's Lodi region are trying to figure out what is damaging their grapevines, and local authorities are investigating whether a company that sprayed herbicides to clear vegetation from an island in the nearby Sacramento River Delta is to blame. While so far there has only been evidence of damage to leaves and shoots, the farmers worry that lab tests may find chemical traces in fruit, rendering their grapes unfit for sale.

The problem may stem from the drought conditions stressing agriculture throughout California. Semitropic Water Storage District, one of California’s eight water storage districts, planned to clear vegetation from 5,900-acre Bouldin Island, reportedly in an effort to harvest water for sale at a later date to water agencies in Alameda, Santa Clara and Kern counties. Semitropic managers did not respond to requests for comment.

Bouldin Island, one of four low-lying islands in the Sacramento River Delta, provides a stopover for migrating Canadian geese and the Sandhill Crane, as well as a potential collection point for water that can be sold and transferred to the growing number of drought stricken agricultural areas. Semitropic leased it from a private company this year. Corn and other crops have been grown there in the past, but the water agency wanted it to lie fallow so water could be collected.

In May, companies hired by Semitropic reportedly sprayed two chemical herbicides—Polaris SP (imazapyr) and Roundup Custom (glyphosate) by air over the island. But sources say that variable wind conditions apparently sent the chemical mixture drifting, over an area as far as 35 miles to the east of the island and smack into the heart of Lodi’s wine country. Growers and others in the industry estimate that as many as 25,000 acres of vines may have been affected.

“We saw symptoms all over the place: yellow spots, leaf deformation, shoot tip deformation and stoppage of growth on the shoot tips,” said Paul Verdegaal, University of California Cooperative Extension viticulture advisor for San Joaquin County. While Roundup is commonly used for weed control by grapegrowers, it's sprayed at ground level. Polaris is not approved for use on edible crops or grapes. Sources say it may have been chosen because it is effective against the type of vegetation found on the island and is considered relatively safe for use around wildlife and humans.  

The San Joaquin County Agriculture Commissioner’s office, in conjunction with the California Department of Pesticide Regulation, is conducting an investigation into the incident. According to interim commissioner Gary Caseri, the investigation should be completed within a few weeks.

A press release from the Ag Commissioner’s office on July 11 stated, “The SJCAC conducts investigations into such cases of alleged crop damage from pesticides that did not stay on target (drift) for the intended field of application. As part of the investigation the SJCAC is responsible for determining the circumstances surrounding the drift incident, however, no determination is made as to the extent of actual damage. Should a pesticide applicator or those involved in the incident fail to follow pesticide label directions or laws and regulations meant to keep pesticides confined to the target fields they may be subject to administrative civil penalty fines by the SJCAC or prosecution by the district attorney’s office."

If the spraying at Bouldin is to blame, however, it's not clear who is responsible. Semitropic leased the land and then hired an agricultural firm, Wilbur-Ellis, which recommended and supplied the chemicals but did not spray them.

Wilbur-Ellis released a statement, “We were not connected to the circumstances surrounding the aerial application. Nonetheless, we do want to support the collection and monitoring of data regarding impact with the goal of working together toward a successful harvest." The firm said Alpine Helicopter Service, based in Woodbridge, performed the spray. That company could not be reached for comment.

While only vines are showing damage now, any wines containing significant residues of chemicals unapproved for use on grapes cannot legally be sold. “Wineries and growers are currently doing due diligence. Sampling is occurring to ensure there are no residues in any products," said Amy Blagg, executive director of the Lodi District Grapegrowers Association. "From what I hear, residues are not being found.” Locals are being cautious, knowing that jumping to conclusions could damage the image of Lodi wines.

“Fruit clusters don’t seem to be affected at this point," said Verdegaal. "My take is that the drift concentrations were so low that there will be no problems with residues, but no one knows for sure yet. It may take another six to eight weeks before harvest. Then we will know for sure.”

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