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Grapevine Pests Found in Nursery Shipments

Inspectors discover sharpshooter eggs in California tree deliveries

by Paul Franson
Glassy-winged sharpshooter is a known vector of the grapevine virus Pierce’s disease. Photo source: Ken Peek/Alameda County Department of Agriculture
Napa, Calif.—Shipments to eight counties in California recently were found to contain viable glassy-winged sharpshooter eggs in crape myrtle plants that originated from a broker in San Diego County, Calif.

The discoveries were from plants shipped to 30 different plant retailers in 13 counties—most of them in Northern California and a few in California’s San Joaquin Valley. All of the counties inspect incoming material for various pests including the sharpshooter, which spreads Pierce’s disease, a serious threat to grapevines and the state’s wine industry. Eggs were discovered in at least eight shipments.

On the morning of May 22, inspectors from the Napa County (Calif.) Agricultural Commissioner’s office discovered two glassy-winged sharpshooter egg masses later determined to be viable during a plant shipment inspection at a local plant retailer.

The egg masses were found on two different crape myrtle trees. Other plants that were part of the shipment were thoroughly inspected and found to be free of any GWSS egg masses.

The shipment originated from a north San Diego County broker-nursery that is not located in a GWSS-infested area but may have included plants from other Southern California counties.

The compliance agreement issued to the particular nursery did not require the plants to be treated with an insecticide.

What happens now
Sharpie the glassy-winged sharpshooter visits the Napa County Fairgrounds to educate children during Ag Day. Photo: Balzac Communications & Marketing
The egg masses found in Napa were driven to the California Department of Food and Agriculture lab in Sacramento, Calif., for identification and determination of viability.

Both egg masses were determined to be the sharpshooters and viable by a CDFA entomologist. Staff from CDFA’s Pierce’s Disease Control Program began an investigation May 30.

Napa County wrote a notice of rejection for all of the plants delivered. The crape myrtles were picked up around 1:30 p.m. on May 22, and the rest of the plants were picked up for return to the shipping nursery May 23.

In addition to contacting CDFA, Napa County also notified other Bay Area counties of the pest finds.

Viable egg masses were subsequently found on crape myrtles that were part of shipments at three different Sacramento County stores. Results from egg mass samples sent to the CDFA lab from other county departments of agriculture are pending.

The investigation by CDFA and the San Diego County Agricultural Commissioner’s Office is ongoing and will determine the breakdown in protocols that led to the trees being sent to Northern California with viable GWSS egg masses.

The San Diego County nursery has been fined for violations in the past, but the San Diego Agricultural Commissioner’s office is not identifying it due to the ongoing investigation.

The nursery will have its shipping privileges suspended and may face administrative civil penalties including fines and suspension. Jim Wynn of the San Diego Agricultural Commissioner’s Office says his department hopes to complete the investigation in a few weeks, but it’s a complex case due to the number of shipments.

Other counties may also seek action against the nursery. “We want aggressive action to send a message that this behavior is unacceptable,” said Napa County Agricultural Commissioner Greg Clark. “It’s a huge threat to an important industry.”

Keeping Napa free of glassy-winged sharpshooters
Napa County has kept the bug from getting a toehold for almost 15 years by mandating rigorous inspections and quarantine while fostering cooperation between the Ag Commissioner’s Office, UC Extension specialists and local growers.

“We’ve never found glassy-winged sharpshooters in Napa County outside plant shipments,” said Clark said. “ This recent discovery of viable GWSS egg masses points to the continued importance of our GWSS exclusion and detection programs.”

“We will work with CDFA and counties throughout the state to ensure the effectiveness of the GWSS program and have Napa County inspectors remain vigilant inspecting plant shipments.”

He also noted that the county, like many others, is continuing an aggressive educational campaign against the sharpshooters. The Napa County Board of Supervisors recently designated May as glassy-winged sharpshooter awareness month. Homeowners are asked to buy their plants only from certified Napa County plant retailers where plants are thoroughly inspected for any signs of GWSS or other serious pests.

Information about GWSS and other pests is available at the Napa Agricultural Commissioner’s website

Clark also reminded readers that the Pierce’s Disease/GWSS Program is up for renewal. The California Assembly passed AB 1642 on May 27 without a single “no” vote. AB 1642 would extend the Pierce's Disease/Glassy-winged Sharpshooter Program for another five years, subject to a favorable industry referendum in spring 2015. Action in the state Senate is pending.

Posted on 06.04.2014 - 13:27:49 PST
Quick, get bluebird boxes up around your vineyards. They eat GWSS.

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