Vineyard Vigilance Targets Winged Threat to Winemakers

The rows of vines are just starting to fill in with bright green leaves.  On the spring morning we visit this small vineyard in El Cajon, they’re glistening with drops from the previous night’s rain. It’s early in the growing season and the harvest of grapes is months away.  But now is the time the County is keeping close watch for a pest that could sour local winemakers’ dreams.


The European Grapevine Moth has already caused considerable damage to Napa Valley vineyards.  So far, there’s no sign it has reached our county.  And while San Diego may be no Napa, keeping our region free of the insect is essential to protecting local grape growers.

“It feeds on the flowers and budding grapes and just ruins them,” says Brian Burkman, who places and inspects insect traps for the County’s Department of Agriculture, Weights & Measures.

While the County sets traps for a variety of pests, the threat of the European Grapevine Moth, or EGVM, prompted the first-ever trapping specifically focused on vineyards.  That began in 2010, soon after the moth was discovered in Northern California.  The East County plot Burkman stops at this day is one of 18 locations where the County now sets traps.  Some are commercial operations.  The others, like this one, belong to hobbyists.

The traps are checked every two weeks. And when Burkman peers into the trap on this visit, he sees something that catches his eye.  Among the various bugs caught in the adhesive is a moth, about the size and with some of the markings he’s watching for.  

“With a lot of moths, there’s a lot that’s similar.  Similar wing patterns,” Burkman says as he studies it. 

The fact the pest hasn’t appeared in the county makes it harder to identify, because he’s never seen one in a trap.  Plus, their condition after getting stuck in the trap means they don’t always look just like perfect samples staff sees in training.  So he’s taking no chances.

“I don’t think it’s EGVM, but to be safe I want to bring it in,” Burkman says.

Suspect insects are sent to the County entomologist for review, usually the same day.  When the entomologist is not available immediately to look at the actual specimen, field staff often emails a picture to make sure there’s no time lost.  If there’s a positive ID at the County, the insect is sent to the California Department of Food and Agriculture for confirmation.

If the state declares that a target insect has been found, the County will begin heavy trapping in the area: 80 traps within a square mile, checked every day for two weeks.  Should an eradication effort be necessary, the state oversees it..

Wine grapes make up only a sliver of San Diego County’s $1.7 billion agriculture industry.  In 2010, local grapes were valued at $784,977 with vineyards covering 447 acres. But efforts to increase that will depend in part on keeping the moth out of our County.  In the modern world, it would be very easy for them to move here from Napa Valley.

“There’s a lot of transportation between here and there. There are so many ways they could get here,” says Linda Feeley, a Senior Insect Detection Specialist.

The County puts its traps at what are classified as “urban vineyards.”  The state handles those in more rural areas.

As for the moth Burkman found at the El Cajon vineyard?  A few hours later word came back: not a European Grapevine Moth.  But Burkman and his colleagues will keep checking and doing their part to keep the County free of the pest.

Tegan Glasheen is a communications manager with the County of San Diego Communications Office. Contact