In a replay of what in late 2023 and throughout much of 2024 was for many property- and homeowners on 102 square miles in the formerly verdant agricultural communities at the east end of the San Bernardino Valley an unpleasant experience, residents on 74 square miles of southwest San Bernardino County find themselves and their land under a quarantine directive from the California Department of Food and Agriculture.
The same pest that was targeted in the previous eradication/control effort, the oriental fruit fly, is again what is being targeted.
Previously known by the scientific name, Dacus dorsalis and now referred to as Bactrocera dorsalis, the oriental fruit fly is a species of tephritid fruit fly that was endemic to Southeast Asia. It is a major pest species, with a broad host range of cultivated and wild fruits. Having left its native Asia, it is a highly invasive pest that now has a presence in at least 65 countries. It is believed to have invaded Hawaii in 1945 as a contaminant of military material returning from the western Pacific war zone, in particular Taiwan and the Mariana Islands. Fruit imported to the mainland from Hawaii is generally fumigated to prevent the pest from coming to the Mainland. But fruit brought by travelers, most likely from Hawaii but also from Southeast Asia and other Pacific islands has allowed the flies to get into California.
On September 27, 2023, the Animal and Plant Health Inspection Service (APHIS) and the California Department of Food and Agriculture imposed a quarantine in San Bernardino and Riverside counties. The quarantine covered 102 square miles of San Bernardino County. Redlands, which is one of the communities in San Bernardino County which has preserved significant portions of historic agricultural property, was at the epicenter of the infestation.
Within the expansive quarantine zone, 1,200 acres of commercial agriculture production of citrus, apples, avocados, peaches and other stone fruits were affected.
It took several months for word about the quarantine to pervade the affected population, and the restrictions began in earnest in January 2024
The California Department of Food and Agriculture, known by its acronym CDFA worked in coordination with the United States Department of Agriculture (USDA), the Riverside County Agricultural Commissioner, and the San Bernardino County Agricultural Commissioner in arresting the migration of the pest, doing so with the cooperation of the local populace, which complied, for the most part, with orders to refrain from removing fruit from trees and further demands that they not move any produce from their property. If fruit fell from trees, residents were urged to double-bag it and place it in a trash bin rather than green waste bins or other organic refuse designations.
Work crews consisting of a combination of California Department of Food and Agriculture and U.S. Department of Agriculture employees, California Conservation Corps crews, and private contractors specializing in fruit removal then methodically worked their way from one end of the target area to the other, going on to private property to pick up the contaminated, or potentially contaminated, fruit, disposing it into containers from which it was impossible for the flies, larvae or maggots to escape.
California and its fruit industry have been buffeted over the years by several pests, including Mediterranean, Mexican, Tau, melon, peach and guava fruit flies. Oriental fruit flies are most easily distinguished from other flies by their yellow color.
In August 2024, the California Department of Food and Agriculture declared an end to the Oriental fruit fly quarantine in the Redlands area following eradication of the invasive species. At that point, according to officials, the nearly 11-month-long collaborative effort to eradicate four unique invasive fruit fly species (Tau, Queensland, Mediterranean and Oriental) from seven quarantine areas across seven California counties — San Bernardino, Riverside, Los Angeles, Ventura, Santa Clara, Sacramento and Contra Costa – concluded with a success.
The California Department of Food and Agriculture, nevertheless, stated at the time that “the threat of new fruit fly introductions remains. Left unchecked, they can endanger the state’s natural environment, agriculture, and economy.” Agricultural officials called upon the state’s residents to remain vigilant for signs of invasive species.
It seems the Bactrocera dorsalis has returned to Southern California, this time further to the west and some 25 miles closer to the Pacific Ocean than in 2023.
Yesterday, September 25, 2025, the California Department of Food and Agriculture declared a 131-square-mile area of Riverside and San Bernardino counties to be under quarantine.
In this case, it was flies found in the cities of Ontario and Jurupa Valley and nearby areas that triggered the alarm. California Department of Food and Agriculture officials have declared 57 square miles in Riverside County and 74 square miles in San Bernardino County as the circumscribed restricted property. Intense monitoring in those areas began in early September, which produced confirmation of infestations in the area. For internal California Department of Food and Agriculture purposes, the commitment for the commencement of the quarantine came on September 19.
“To prevent the spread of Oriental fruit flies through homegrown fruits and vegetables, residents living in the quarantine area are urged to not move those items from their property,” according to the California Department of Food and Agriculture website. “However, home grown produce may be consumed or processed (i.e., juiced, frozen, cooked, or ground in the garbage disposal) on the property where they were picked, or disposed of by double bagging and placing in the regular trash, not in green waste receptacles.”
According to the website, “Following the principles of integrated pest management, agricultural officials use the “male attractant” technique as the mainstay of the eradication effort for this invasive species. This approach has successfully eliminated dozens of fruit fly infestations in California. Trained workers apply a small amount of fruit fly attractant mixed with a very small dose of an organic pesticide, Spinosad, approximately 8-10 feet off the ground on street trees and similar surfaces. Male fruit flies are attracted to the mixture and perish after consuming it. The male attractant technique is being carried out over an area that extends 1.5 miles from each site where oriental fruit flies have been trapped.”
Female flies lay eggs in groups of three to 30 under the skin of host fruits, according to the California Department of Food and Agriculture. Larvae tunnel through the host and emerge approximately 10 days later. Flies mature into adulthood in 10 to 12 days and usually live up to 90 days. Adult flies are strong fliers and can travel as far as thirty miles for sustenance. This aggressive search for food allows the pest to infest a region quickly.