California agriculture officials are urging residents and travelers to stop bringing or shipping fresh fruit into the state as invasive fruit fly quarantines remain active in San Diego County.

The warning comes during peak summer travel, when luggage, online purchases and personal shipments can create easy pathways for invasive pests to enter California. Officials say even a small piece of infested fruit can threaten home gardens, local food access and the state’s $50 billion-plus agriculture industry.

In a media briefing on August 18, hosted by American Community Media, a panel of experts discussed the negative effects of the fruit flies on California’s crops and how we can prevent any further spread of the invasive species.

Speakers

  • Victoria Hornbaker, CDFA Plant Health and Pest Prevention Services Director
  • Abraham Lopez-Zuniga, CDFA Emergency Response Team Lead
  • Jordan Petersen, Los Angeles County Deputy Agricultural Commissioner/Sealer
  • Huong Dang, Orange County Agricultural Commissioner’s Office

Unlike native insects, invasive fruit flies such as the Mediterranean, Mexican and Oriental fruit fly have no natural predators in California. They can damage more than 250 types of produce from the inside out, putting at risk a state that grows more than 400 commodity crops, including over three-quarters of the nation’s fruits and nuts and one-third of its vegetables.

California faced the largest invasive fruit fly outbreak in the century-long history of the California Department of Food and Agriculture in 2023, when seven quarantines were active at the same time. Though several infestations have since been eradicated, officials say the threat remains serious.

Two Mexican fruit fly quarantines are still active across roughly 111 square miles in San Diego County, even as at least two other quarantined infestations have been eradicated this year.

“We are winning,” said Victoria Hornbaker. “They continue to come at us, but between the CDFA, the USDA and the counties, we continue to eradicate those fruit flies.”

How Pests Enter California

Officials said invasive fruit flies most often enter California through three routes: travelers carrying fruit or plants in luggage, purchases from unverified online marketplaces and produce shipped from other states or countries, including fruit sent by relatives and friends from home gardens.

Hornbaker said California’s strategy is built around prevention. The state operates a network of inspectors, more than 100,000 traps and 16 border protection stations along the Oregon, Arizona and Nevada lines.

At airports and the California-Mexico border, CDFA also works with the U.S. Department of Agriculture’s “Beagle Brigade,” a team of detector dogs and handlers trained to screen luggage for fruit and plant material.

“If fruit flies become established in California, it’s going to be devastating to California’s agriculture and can have irreversible impacts to our home gardens … We’re not just talking about protecting commercial agriculture,” Hornbaker said.

She warned that a permanent infestation could mean higher grocery bills and less access to fresh produce for families across the state.

Invasive pests cost the United States roughly $40 billion annually, while California faces more than $3 billion each year in crop losses, native plant damage and control or eradication efforts.

The challenge has grown with the rise of online shopping and personal shipping. Jordan Petersen said an estimated 8 million packages enter California every day.

Finding the few that may contain risky agricultural material, she said, can be “a bit like trying to drink from a fire hose.”

Detector Dogs on the Front Lines

Los Angeles County, home to nearly 10 million residents and a major hub for international travel and shipping, employs 75 inspectors who place and check pest traps throughout the year.

The county also operates six detector dog teams that screen parcels at FedEx, UPS and U.S. Postal Service facilities. The dogs do not detect the insects themselves. Instead, they alert handlers to packages containing fruit or plant material, which inspectors then open and examine.

“It’s about finding that invasive pest while it’s still inside the package before it has the opportunity to reach our communities,” Petersen said.

Her teams have intercepted pests hiding on mangoes, guava, grapefruit, pineapple and truffle plants, “just to name a few.”

In Alameda County, Lisa Sampson said her dog Tank has detected 19 invasive fruit fly finds since the pair began working together in 2023.

“Which is pretty high. It definitely shows a trend in changes that I’ve seen throughout the program in my time since 2011, where we didn’t see as many fruit flies. It was pretty rare. It’s becoming pretty common,” Sampson said.

Detector dogs are trained at the National Detector Dog Training Center, where each dog is tested on five fruit odors before entering the field. They first work at parcel terminals for a year before being cleared to screen post office bins.

The dogs “have to be 90% or better field certified” every year, Sampson said. “You need a high energy-dog … They usually calm down in their work environment.”

When a Fruit Fly is Found

When an invasive fruit fly is found in a trap or inspection, officials move quickly.

A single detection can trigger “delimitation,” a process in which additional traps and inspectors are sent to the area to determine whether the fly was isolated or part of a larger infestation. Multiple detections can lead to eradication efforts, including organic bait stations that attract male flies and, in some cases, removal of fruit around the site.

If enough flies are found, the area may be placed under quarantine. Quarantines generally last through three life cycles of the fly, which can mean several months in summer and longer during winter.

For residents living under quarantine, Abraham Lopez-Zuniga said one major rule is simple: do not give away fresh fruit or vegetables from the quarantined area.

“You can process the fruit, you can juice the fruit, you can bake the fruit, and then you can give it away,” Lopez-Zuniga said.

Fruit that appears infested should be double-bagged and placed in the regular trash, not the green bin. Residents can report suspected infestations to CDFA at 1-800-491-1899 or through the agency’s online reporting system.

When quarantine rules are violated, counties can deny entry to noncompliant shipments, destroy infested products, usually by deep-freezing, and notify buyers through a formal notice, Petersen said. CDFA also places compliance agreements on local nurseries and growers and hold notices on properties where invasive pests are found.

A Warning for Home Gardeners

Officials also urged gardeners to be careful when buying exotic plants or fruit trees online.

Huong Dang, an Orange County gardener who also works in administrative support for the county agricultural commissioner’s office, said demand for specialty plants has grown in Vietnamese-speaking gardening communities. That demand has pushed some buyers toward unregulated sellers on Facebook Marketplace and Etsy instead of licensed nurseries and growers.

“Some people receive something totally different from what was advertised, and many of the plants are not suitable for the conditions of growing here,” Dang said.

She encouraged gardeners to work with local nurseries instead.

“Fellow gardeners, better contact your local nursery. If they don’t carry it, they can special order for you,” Dang continued. “The plants are certified pest- and disease-free.”

Hornbaker said the public remains one of the most important lines of defense.

“We always want to stress: Don’t pack a pest. We don’t want people bringing back fruits, vegetables, plants and natural materials into California.”

 

All images courtesy of American Community Media