In March, when CDFA announced the first Mexican fruit fly quarantine in La Mesa, NBC 7 San Diego reported that officials expected the quarantine to end "around September." September came and went. The quarantine now covers all of Spring Valley's zone and La Mesa's in a single 173-square-mile area, and San Diego County's Agriculture, Weights and Measures department expects it to continue through spring 2027.
March's estimate was reasonable for March. The quarantine doesn't run to a date on a calendar, though. It runs on a countdown, and a new find starts the countdown over. If you have a lemon, guava or persimmon tree in Spring Valley, that's why your fruit has to stay on the property for the rest of the winter.
The Countdown Starts Over With Every Find
A quarantine is triggered by any of three things: five wild adult flies, one mated female, or an immature stage such as a larva. Once it's in place, the end date is tied to the fly's biology. The California Department of Food and Agriculture's current emergency program, amended September 11, 2026, runs until April 28, 2027. CDFA describes that as the time needed to carry out its treatment plan "across three life cycles" of the fly. CDFA's trapping plan also keeps monitoring for three fly generations after the last detection.
The program notice draws the program area as every property within 4.5 miles of every detection. Studies cited in the notice have the flies traveling about 100 meters a day and three to five miles over an adult's life. So each new catch adds another 4.5-mile circle to the map and adds time to the countdown.
That explains how a quarantine expected to wrap up in early fall now stretches past the next citrus harvest.
How Spring Valley Ended Up Inside It
The neighborhood got pulled in during the summer, in a series of steps:
- February 5, 2026. Two male flies are trapped in La Mesa. A mated female with developed eggs follows on February 24, and five flies in all are confirmed between February 5 and 26.
- March 10. CDFA announces a 77-square-mile La Mesa quarantine bounded by the San Diego River, Sweetwater Reservoir, I-15 and El Cajon. Expansions on March 17 and April 2 bring the federal version to 84 square miles.
- June 4. A mated female is detected in Spring Valley. Another turns up in El Cajon on June 12.
- June 16 and 18. A Spring Valley quarantine of about 76 square miles is set up, then expanded to about 111 square miles after the El Cajon find. CDFA's June 22 announcement notes that the Spring Valley area overlapped the La Mesa zone by 19 square miles.
- August 4. A mated female is found in a tangelo in La Mesa.
- August 14. CDFA merges the two zones into one 173-square-mile quarantine.
CDFA's September count puts the total at 19 adult flies trapped in El Cajon, La Mesa and Spring Valley between February 5 and August 11. On September 23, the USDA's Animal and Plant Health Inspection Service expanded the federal quarantine to match the area CDFA had already set in August.
The boundary is long and irregular. The federal legal description runs along State Route 94, Proctor Valley Road, State Route 125 and Paradise Valley Road, among many other markers. Street names won't settle whether a particular house is inside, so the reliable check is CDFA's interactive quarantine map, linked from the CDFA Mexican fruit fly page.
What Stays on the Property
The household guidance hasn't changed since spring. Because the zone got longer and bigger, it now applies through the whole winter. Here is CDFA's resident guidance as written:
"Fruits and vegetables may be consumed or processed (i.e. juiced, frozen, cooked, or ground in the garbage disposal) at the property of origin. If they are not consumed or processed, dispose of them by double-bagging them in plastic bags and putting the bags in the garbage bin for collection."
The County's Mexican fruit fly page adds a few points of its own:
- Don't move any fruits or vegetables off your property.
- Bagged fruit goes in the garbage bin, not the green waste bin.
- Let agricultural crews onto your property so they can find and stop the pest.
- Report suspicious pests to CDFA's pest hotline at (800) 491-1899.
In practice, the guidance treats a bag of lemons for a neighbor or a box of guavas for the office the same way as any other fruit leaving the yard. The fruit can be eaten, juiced, frozen or cooked where it grew. Commercial growers are handled separately: they can apply for a compliance agreement to keep shipping, processing, harvesting or selling, by emailing [email protected] or calling (858) 614-7770.
The Trees on the List
The fly that brought the quarantine to Spring Valley was caught in a trap in an avocado tree at a home in the neighborhood. Avocado is on the host list, but the County lists Hass as exempt. The APHIS host list limits that exemption to mature green Hass.
The rest of the list covers a lot of typical East County yards. It includes orange, lemon, grapefruit, mandarin and tangerine, plus persimmon, apple, pear, peach, pomegranate, guava, passionfruit and white sapote. The County also lists apricot and cherimoya, and notes that some citrus varieties are exempt. One of the La Mesa detections was in a loquat tree. For any tree you're unsure about, the full host list is the place to check.
Who You Might See on Your Block
Because the countdown is still running, eradication work goes on alongside the household rules. The September 11 program notice lists three methods.
Sterile fly releases. Aircraft release sterile male flies within 3.5 miles of each detection site, every three to four days, over two fly life cycles. That typically takes four to six months, depending on temperature. Wild females that mate with sterile males lay infertile eggs, which breaks the breeding cycle.
Bait spray. Ground crews spray a protein bait containing an organic spinosad formulation, GF-120 NF Naturalyte Fruit Fly Bait, on host plant foliage within 200 meters of each detection. They repeat it every seven to 14 days for one life cycle.
Fruit removal. If there's evidence of a breeding population on a property, such as immature stages, a mated female or multiple adults, crews remove all host fruit from that property and from every property within at least 100 meters of it. The fruit goes to a landfill.
Unless CDFA needs an inspection or abatement warrant, residents get written notice at least 48 hours before bait spraying or fruit removal on their property. Afterward, crews leave a completion notice listing precautions and any post-harvest waiting periods for fruit still on the property. CDFA's work plan allows treatment on residential lots, shared residential areas, and public rights-of-way. It excludes bodies of water and undeveloped native vegetation. Trapping uses McPhail traps baited with torula yeast, and trap density goes up around any new find.
Where Shared Backyard Fruit Used to Go
The rule also affects fruit that used to leave the neighborhood for good causes. In April, back when the zone covered only La Mesa, Times of San Diego reported that the nonprofit ProduceGood had paused some local harvesting because of the quarantine. According to the outlet, ProduceGood kept up its distributions at La Mesa First United Methodist Church and Journey Community Church using produce grown outside the zone. It had collected 1,000 pounds and delivered 3,000 pounds in La Mesa over the previous six months, and five more growers were ready to donate when the quarantine began.
That report came out four months before the August merger stretched the same rules across Spring Valley and El Cajon. Under the current guidance, any tree inside the 173 square miles falls under the same rule. Its fruit is for the household that grows it, or for the garbage bin, until the quarantine lifts.
When it lifts depends on the countdown. County officials expect spring 2027, and CDFA's emergency program runs through April 28, 2027. Neither one is a guaranteed end date, because a new detection would add time just as the summer detections did. Your best way to keep track is the CDFA quarantine page and its map.
This post is general information about a state agricultural quarantine. It isn't legal advice, so check your own property and questions directly with CDFA or the County's Agriculture, Weights and Measures office.
Fruit trees are part of what makes so many Spring Valley yards feel like home, and we've walked plenty of East County buyers past a backyard lemon tree. If you're thinking about selling and want a team that keeps up with the details of your yard, including this winter's quarantine rules, Lyle + Grace Team is glad to talk it through. Sell Your Place with Lyle and Grace.
