The Oriental Fruit Fly has been eradicated in Santa Clara County, Calif., prompting local, state and federal agriculture officials to declare an end to a quarantine for the area.

However, California’s fruit fly invasion is still "reaching critical mass,” according to an expert at the University of California, Davis.

The declaration in Santa Clara comes nearly nine months after officials first detected populations of the Oriental fruit fly in the area and established a quarantine encompassing parts of Sunnyvale, Santa Clara, Cupertino, San Jose, Milpitas, Mountain View, Saratoga, Campbell and Los Altos.

“Thanks to the responsiveness and cooperation of Santa Clara’s residents, and our partners at the Santa Clara County Division of Agriculture and the United States Department of Agriculture, we were able to quickly and safely eradicate this infestation of the Oriental fruit fly,” said Victoria Hornbaker, Director of the state Department of Food and Agriculture’s Plant Health and Pest Prevention Services Division.

 “As with so many invasive species, when we can detect infestations early and respond promptly, we stand the best chance of protecting our backyard fruits and vegetables and ultimately safeguarding California’s agricultural heritage,” she said.

Related:Fruit removals begin in quarantine zones

During the quarantine, crops that are hosts for the invasive pest — which include more than 300 varieties, such as citrus and other fruits, nuts, vegetables and berries — were not allowed to be moved from the properties where they were grown. Commercial crops were required to meet stringent treatment or processing standards before being harvested or moved.

While the Santa Clara County quarantine area has been lifted, there are currently six other active fruit fly quarantines in California, which still threaten California’s natural environment, agriculture and economy.

So the Golden State’s fruit fly battle is far from over, notes UC Davis distinguished professor James R. Carry, an authority on the invasion of tropical fruit flies in California.

"After seven decades of near-continuous outbreaks in scores of California cities, tephritid fruit fly invasions (e.g., Mediterranean, oriental, peach, and Mexican fruit flies) are reaching critical mass, with many of the annual eradication programs morphing into below-the-radar, never-ending fruit fly control programs," Carey says in a research abstract. "Permanent establishment of any one of these tropical species has the potential to shut down the multi-billion dollar domestic and foreign markets for hundreds of California fruit and vegetable crops."

Related:Fruit fly quarantine expands in California

From Trickle to Flood

Carey served on the CDFA's Medfly Scientific Advisory Panel from 1987-1994, testified to the California Legislature "Committee of the Whole" in 1990 on the Medfly Crisis in California, and authored the paper "Establishment of the Mediterranean Fruit Fly in California" (1991, Science 258, 457).

Eleven years ago (April 2013), he delivered a seminar to the Department of Entomology and Nematology on "From Trickle to Flood: The Large-Scale, Cryptic Invasion of California by Tropical Fruit Flies."

"Despite aggressive and costly efforts by government agencies to prevent their introduction, establishment and spread, California has experienced an inexorable march of tropical fruit flies (Tephritidae) into the state with three-fold more species detected and thousands more flies captured than in all other mainland U.S. states combined," Carey related in his 2013 abstract.

"Since 1954 when the first fly was detected, a total of 17 species in 4 genera and 11,386 individuals (adults/larvae) have been detected at over 3,348 locations in 330 cities," he told the 2013 seminar attendees. "My colleagues and I conclude from spatial mapping analyses of historical capture patterns and modeling that, despite the approximately 250 emergency eradication projects that have been directed against these pests by state and federal agencies, a minimum of 5 and as many as 9 or more tephritids are established and widespread. This list includes three of the most economically-important species in the world—the Mediterranean, Mexican and oriental fruit flies."

Carey, a member of the UC Davis faculty since 1980, is a senior scholar in the Center for the Economics and Demography of Aging at UC Berkeley and former vice chair of the UC Davis Department of Entomology. He focuses his research on  insect biodemography, mortality dynamics, and insect invasion biology. 

He will present a Department of Entomology and Nematology seminar on "California's Fruit Fly Invasion Crisis" at 4:10 p.m., Monday, June 3 in Room 122 of Briggs Hall, UC Davis campus. It also will be on Zoom.

CDFA urges caution

As the temperatures rise and vacationers ramp up their travel plans, local agricultural officials are urging residents to refrain from bringing back potentially infested produce from their trips. While you’re at home, we urge residents to continue to stay vigilant for signs of invasive pests and cooperate with local officials.

To help prevent any future introductions of invasive species, state officials follow these guidelines:

To learn more about invasive species and how to protect the county’s fruits and vegetables, visit CaFruitFly.com or ag.santaclaracounty.gov.

Source: California Department of Food and Agriculture, University of California, Davis.