Exotic fruit flies attack over 400 types of plants. Recently, USDA announced $103.5 million to protect fruit, vegetable and livestock industries as part of its invasive fruit fly programs. And the agency’s efforts appear to be paying off.

In late August, California and federal agriculture officials announced the eradication of all populations of invasive fruit flies from the state.

The joint eradication effort addressed infestations from five introduced species: Oriental (Bactrocera dorsalis), Tau (Zeugodacus tau), Queensland (Bactrocera tryoni), Mexican (Anastrepha ludens) and Mediterranean (Ceratitis capitata) fruit flies, the USDA explains.

With their successful eradication, quarantines have been lifted across Contra Costa, Los Angeles, Orange, Sacramento, San Bernadino, Santa Clara, San Diego, Riverside, and Ventura Counties, freeing thousands of acres of commercial agriculture from restrictions.

However, the work to keep exotic fruit flies at bay is ongoing. The California Department of Food and Agriculture announced Sept. 6 that a new quarantine was establish in part of Alameda County for the Mediterranean fruit fly following the detection of one wild mated female in Fremont.

“The United States is experiencing an unusually high number of invasive fly detections --- the worst of its kind in 70 years,” said Mark Davidson, who administers USDA’s plant protection and quarantine program.

Related:Fruit removals begin in quarantine zones

“Invasive fruit flies are a destructive nuisance that drives up production costs for fresh fruit and vegetable production” to the detriment of both producers and consumers, he said. “Our new five-year plan lays out how federal and state partners can continue to limit fly spread as we develop better pest management tools and options.”

Troublesome flies

Of particular note to the West Coast has been the oriental fruit fly that migrated from Asia/Africa to Hawaii in the 1940s before being initially discovered in mainland California before increasing further as international travel has increased.

The fly attacks more than 400 types of fruits and vegetables, particularly tomatoes, figs, cherries, and apricots. The pest has been known to destroy entire crops, effectively disrupting trade, and resulting in financial loss to agricultural production.

Another regional nemesis that arrived in central Mexico in the late 1800s and continued its northward travels to the California-Mexico and Texas-Mexico border is the Mexican fruit fly that particularly enjoys consuming more than 50 types of fruits and vegetables with a particular affinity for citrus.

Related:Fruit fly quarantine expands in California

In Texas, deterrent efforts are in a tiered layer, first surveying the extent of an incursion, conducting public outreach and establishing a quarantine in the affected area. The sterile insect program uses large amounts of sterile male fruit flies to mate and, because of their sterility, produce no offspring, thus reducing and/or decimating the wild fruit fly population.

Portions of northern Mexico and southern Texas are weekly recipients of an average 165 million sterile Mexican flies to support eradication along the border.

Another border state, Arizona, recently breathed a sigh of relief after a single male Mexican fruit fly was discovered during routine trapping in an industrial sector of Phoenix along Interstate 10.

An immediate Department of Agriculture response effort trapping was initiated where water and yeast traps were placed and serviced within a large corridor from the initial site. After a six-month effort, Jack Peterson, an Associate Director reported: “We went through two lifecycles of trapping over an 81 square mile grid and no further Mexican fruit flies were detected.”

USDA’s Animal and Plant Health Inspection Service web page does list active federal quarantines in certain crop, forest, or urban areas of the state where pests or diseases could survive year-round (including Mediterranean and European cherry fruit flies).

Unprecedented outbreak

The 2023 invasive fruit fly outbreak in California was unprecedented, marking the worst of its kind in CDFA’s 100-year history, officials said. The outbreak included first-ever quarantines for Tau and Queensland fruit flies in the U.S. and Western Hemisphere, prompting U.S. Agriculture Secretary Tom Vilsack to allocate the $103.5 million from the Commodity Credit Corporation to APHIS.

Federal, state and local agricultural commissioners deployed hundreds of employees for trapping, fruit removal and survey activities. Their efforts included the release of sterile Mediterranean and Mexican fruit flies to disrupt the pests’ reproduction as well as the use of an organic treatment called Spinosad, according to USDA.

With the new outbreak in Alameda County, sterile male medflies will be release in the area, with 250,000 males per square mile per week to be deployed in a 39-square-mile area, the CDFA explained. In addition, properties near detection sites are being treated with Spinosad to help reduce the population, and fruit removal will occur near properties with mated females, larval detections and/or multiple adult detections, the agency said.

“We have had a very difficult year with invasive fruit flies in our state,” CDFA Secretary Karen Ross said, “and this cash investment puts us in a stronger position to eradicate infestations as quickly as possible while evaluating commercial pathways and other factors to better understand why detections have increased.”

Ross emphasized the importance of public cooperation in these efforts. “We are proud of what we have accomplished with the help of California residents,” she said. “Your support was vital to eradicating these pests and remains essential in protecting our food supply and natural resources from future invasive threats.”

Plan of action

Ross also outlined steps that people in California can take to help prevent future infestations:

For online reporting, visit www.cdfa.ca.gov/plant/reportapest/ or email [email protected]. You may also contact your local county agricultural commissioner’s office.