Marin targets bug with taste for grapes

A destructive insect that could have serious adverse impacts for wineries and agricultural water use was discovered in Marin County last week, county officials said Wednesday.

An official with the Marin County Department of Agriculture found a glassy-winged sharpshooter last Thursday while inspecting a shipment from a nursery in Ventura County, according to county officials. That shipment has since been returned, but the name of the nursery that sent it is being withheld to prevent unwanted attention, according to the Department of Agriculture.

The glassy-winged sharpshooter is known to feed on more than 300 plants, including grapevines and almond trees, many of which are found in Northern California. Apples, blackberries and eucalyptus trees are also among the affected species of plants. Once attached to a host plant, the glassy-winged sharpshooter can drain 200 to 300 times its own body weight in water every day.

A tree that has been heavily infested can lose 10 to 15 gallons of fluid each day, requiring farmers to significantly increase irrigation, according to the Department of Agriculture. Marin County Agricultural Commissioner Stacy Carlsen said in a statement that the glassy-winged sharpshooter’s impact on water use is especially concerning due to California’s ongoing drought.

Deputy Agricultural Commissioner Stefan Parnay said the bug is particularly hazardous to grapes because it can transmit the bacteria that causes Pierce’s disease. “There’s no cure for that, and it will kill the grapevine,” Parnay said.

According to www.piercesdisease.org, the condition affects the plant’s ability to conduct water through its xylem, resulting in chlorosis and scorching of the leaves. Parnay described the adult glassy-winged sharpshooter as being roughly half an inch long and an eighth-inch wide. He compared the bug’s size to the width of a dime.

The Marin County Department of Agriculture is asking anyone who suspects they may have found a glassy-winged sharpshooter to call (415) 473-6700 or (415) 473-4204 as soon as possible. Specimens can be taken to 1682 Novato Blvd. in Novato for identification during regular business hours.

There is a history of glassy-winged sharpshooter infestations in at least two other Bay Area counties. Santa Clara County has been battling glassy-winged sharpshooters since 2008 and there’s still one active infestation there, according to that county’s Deputy Agricultural Commissioner Eric Wylde:

“We’re down to very low numbers, which makes them difficult to detect, but every once in a while they pop up.”

There was also a glassy-winged sharpshooter infestation in Contra Costa County in 2001, but officials conducted a successful eradication effort, according to Matthew Slattengren, assistant commissioner of the Contra Costa County Department of Agriculture.