- Author: Sandipa Gautam
Invasive Fruit Fly Quarantine
What to know as a SJV citrus grower?
Sandipa Gautam
Area Citrus IPM Advisor
UC Statewide IPM Program Operations
Several species of invasive fruit flies that belong to the family Tephritidae are considered serious pests of hundreds of agricultural crops including citrus. These flies lay eggs on or near the fruit surface, and when the maggots hatch, they bore into the fruit, making it unfit for human consumption and causing major losses to fruits and vegetable production. California is experiencing an unusually high number of invasive fruit fly detections in the 2023/24 season and several areas in California are now under a fruit fly quarantine. For many invasive fruit fly species, quarantine is triggered when two or more adult flies are caught in a trap or by a single detection of larvae or pupae indicating a breeding population. Core area is 0.5-mile radius around the detection site and a quarantine area is 4.5-mile radius around each detection.
Counties Currently Impacted by Invasive Fruit Fly Quarantines:
- Oriental fruit fly: Contra Costa, Riverside, Sacramento, San Bernardino, and Santa Clara Counties (Figure 1)
- Mediterranean fruit fly: Los Angeles County (Figure 2)
- Tau fruit fly: Los Angeles County (Figure 3)
- Queensland fruit fly: Los Angeles and Ventura Counties (Figure 4)
Why is fruit fly quarantine concerning to citrus growers?
Citrus is a known host to all invasive fruit fly species. Fruit fly life cycle begins as eggs laid by adult female on surface or under the fruit rind maggots hatch and bore into the fruit and develop inside the fruit (Figure 5). They drop to the ground and pupate. Many fruit fly species are known to overwinter as prepupae or pupae, but some species like Medfly can overwinter in all life stages inside fruit or as pupae on the ground. Adults emerge in early spring and the life cycle continues. Because eggs and immatures can be present inside the fruit, movement of infested fruit may accidentally transport them to a new area where fruit fly has not been detected.
Invasive fruit flies – what to look for?
Four species of fruit flies are currently regulated in California. The adults may look similar to houseflies but are distinctly different in color and the markings on the body. They are about 5-8 mm in size, much bigger than spotted wing drosophila, another invasive species that has been established in California.
- Oriental fruit fly: ~8 mm size, bright yellow colored body with a dark T shaped mark on the abdomen (Figure 1).
- Mediterranean fruit fly (Medfly): ~5-6 mm in size, yellow-light brown body, clear wings with brown bands (Figure 2)
- Tau fruit fly: ~7 mm in size, yellow body with black markings (Figure 3)
- Queensland fruit fly: ~5-8 mm in size, wasp-like body, reddish brown in color with distinct yellow markings, clear wings with band along the top margin.
Figure 1. Oriental fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024: Contra Costa, Riverside, Sacramento, San Bernardino, and Santa Clara Counties (right).
Figure 2. Mediterranean fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024 – Los Angeles County (right).
Figure 3. Tau fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024: Los Angeles County (right).
Figure 4. Queensland fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024: Ventura County (right).
You can find more information about invasive fruit fly species including interactive quarantine maps, regulatory information and pest profile information below: https://www.cdfa.ca.gov/plant/PDEP/treatment/index.html
Figure 5. Fruit fly larvae are white, legless maggots. They bore into the fruit and feed on pulp. Infested fruit may drop and decay.
What is happening to prevent fruit fly spread?
The California Department of Food and Agriculture (CDFA), in cooperation with the United States Department of Agriculture (USDA) and County Agricultural Commissioners, has initiated local regulatory measures to eradicate and prevent the statewide spread of Queensland fruit fly, Tau fruit fly, Mediterranean fruit fly and Oriental fruit fly. California Citrus Quality Council (CCQC) in coordination with researchers is developing a systems approach that allows for post-harvest treatment of citrus fruit for movement from the core to pack.
What can you do?
If you are a grower inside the quarantine area, follow regulations about harvesting, processing, or storing fruit. Contact your County Ag Commissioner about the latest regulations, or review FAQs here: https://www.cdfa.ca.gov/plant/fruitfly/docs/Invasive_Fruit_Fly_FAQ_Industry_1-18-24.pdf . If your property is under fruit fly quarantine, follow either pre or postharvest treatment protocols from USDA to move fresh fruit
- Grower outside the quarantine area, stay informed, invest in trapping and pre-quarantine treatments to avoid potential harvest delays should a quarantine be established in the future. For information on prevention and exclusion visit: https://www.cdfa.ca.gov/plant/PE/InteriorExclusion/current_preharvest_treatment.html
- Quarantines boundaries can change rapidly, so it is critical to stay in communication with your local agricultural commissioner.
- Report any suspected invasive fruit fly sightings to CDFA, USDA or your local County Agricultural Commissioner.
- Encourage neighbors, friends, and family to avoid moving any homegrown produce from their properties and to cooperate with agriculture officials working in their area.
- Help spread the “Don't Pack a Pest” message to travelers or those receiving produce in the mail or through other shipping channels.
- Share social media posts created or shared by CDFA, USDA or County Agricultural Commissioners.
- Author: Belinda Messenger-Sikes
The invasive pest spotlight focuses on emerging or potential invasive pests in California. In this issue we are covering the Oriental fruit fly.
Oriental Fruit Fly Facts
The Oriental fruit fly (OFF) is an invasive pest that attacks over 230 crops including citrus and other fruits, nuts, vegetables, and berries. The short life cycle of the OFF allows rapid development of serious outbreaks, which can cause severe economic losses. Heavy infestations can cause complete losses of crops. Fruit that has been attacked may be unfit to eat as larvae tunnel through the flesh as they feed. Fungi and bacteria enter, leaving the interior of the fruit a rotten mass. Infested fruit does not always look damaged from the outside but may take on a brown, mottled appearance as the maggots feed.
The adult OFF is slightly larger than a housefly, around 1/3 inch (8mm) in length. The body color is often bright yellow with a dark "T" shaped marking on the abdomen. The wings are clear. The female has a pointed slender ovipositor to deposit eggs under the skin of host fruit. A single female can lay more than 1,000 eggs in her lifetime. The fly can infest new areas very quickly because it is a strong flyer and can travel 30 miles in search of food and sites to lay eggs.
What Can You Do?
The Oriental fruit fly is a major pest of agriculture in Hawaii and efforts to prevent its establishment into California are ongoing. Areas where OFF have been detected are under quarantine. If you are in a quarantine area, you can help by controlling the movement of your homegrown fruit off your property and by disposing of infected fruit in the garbage, not in green waste or compost. If you suspect you've found OFF, notify your County Agricultural Commissioner's office or call the California Department of Food and Agriculture (CDFA) Pest Hotline at 1-800-491-1899.
/h2>/h2>Seven invasive fruit fly quarantines are in place throughout California. If you live within one of these quarantine zones, fruits and vegetables should not be moved off the property they were grown on. Quarantines are in place for the Mediterranean fruit fly, Oriental fruit fly, tau fruit fly, and Queensland fruit fly. Smuggled, illegally imported fruit is the most common pathway of fruit fly entry into California.
These fruit flies lay their eggs under the skin of many crops, making their detection difficult. Females of some species can lay 1,000 eggs in their lifetime. Once eggs hatch, larvae (maggots) feed on the inside of the fruit. Infested fruit drops to the ground where larvae leave the fruit to burrow into the soil to pupate. Numerous generations can occur each year.
Invasive fruit flies pose a major threat to California agriculture as they make fruit unfit for human consumption and damage a wide variety of crops from fruits to vegetables. In addition, they pose an economic burden to commercial growers in quarantine zones as they must treat all host fruit with an approved pesticide before sale or movement within or outside of the quarantine area. You can help prevent the spread of these invasive pests and reduce the risks they pose to commercial fruit and vegetable producers by not moving homegrown produce and cleaning up and disposing of dropped fruit.
Quarantine zones include:
Mediterranean fruit fly
- Los Angeles County, Leimert Park Area
Oriental fruit fly
- San Bernardino and Riverside Counties, Redlands, Yucaipa, Highland, San Bernardino, and Riverside Areas
- Sacramento County, Rancho Cordova Area
- Contra Costa County, Brentwood Area
- Santa Clara County, Santa Clara Area
Tau fly
- Los Angeles County, Stevenson Ranch, Valencia, Santa Clarita Areas
Queensland fruit fly
- Ventura and Los Angeles Counties, Thousand Oaks Area
Quarantine zones updated December 5, 2023. To view the most up-to-date quarantine maps, visit the CDFA webpage at https://www.cdfa.ca.gov/plant/pe/InteriorExclusion/quarantine.html.
If you live in a fruit fly quarantine zone:
- Do not take fresh fruits and vegetables off your property. Don't share with neighbors or ship to friends and family in other counties or states.
- Consume or process (i.e., juice, freeze, or cook) all fruits and vegetables where they are grown.
- Dispose of homegrown fruits and vegetables by double-bagging and sealing then placing them in the trash–not in your green waste or compost bin.
Suspect you have an invasive fruit fly infestation? Contact the California Department of Food and Agriculture (CDFA) Pest Hotline: 1-800-491-1899 or your County Agricultural Commissioner. Allow authorized CDFA workers access to your property to inspect fruit, set traps, or conduct fruit fly eradication activities. Your cooperation helps protect California agriculture!
While the holiday season is a time of giving, we urge you to not share these invasive fruit flies!
[Revised from this California Dept. of Food and Agriculture (CDFA) blog post.]
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- Author: Hamutahl Cohen
Queensland fruit fly quarantine?
Growers should consider the pre-quarantine program.
The Queensland fruit fly quarantine zone has been expanded (see: https://www.cdfa.ca.gov/plant/qff/regulation.html). Queensland fruit fly (also called QFF or Qfly) is a concern because it has over a hundred host plants and causes severe fruit damage. Like other tephritid fruit flies, it is challenging to control once the population takes hold.
What does this mean for growers in the quarantine zone? If a grower is in the zone (regardless of if they have Qfly on their ranch), their crop is on hold for one life cycle. Based on the weather, the life cycle length can vary. In the winter, life cycles are generally around 90 days. In the summer, the life cycle is about 30 days. Growers can view the length of the fruit fly life cycle here to determine how long the holding period is: https://www.cdfa.ca.gov/plant/pe/InteriorExclusion/pdf/QFF_Ventura_County-Thousand%20Oaks-2023-2024PreharvestTreatmentSchedule.pdf
During this holding period, growers must treat their crop repeatedly until the holding period expires. Growers must treat with Malathion + NuLure every 6-14 days for the duration of the holding period. This is a bait spray that must be mixed. To use Malathion, growers will need to notify the county ag commissioner and will need to register for special local need usage. For an additional option, growers can instead use GF-120 Spinosad bait every 7-10 days. GF-120 is premixed and therefore easier to use, but costs more than Malathion. When selecting which bait to use, growers should consider PHI for their crop and harvesting intervals. For example, GF-120 has a 4 hour PHI and Malathion has a 3 day PHI for strawberries – if a grower is harvesting every week, they may want to use GF-120. Growers need to spray bait around the perimeter of each field and throughout the field at spaced intervals.
Growers must comply with the treatment intervals, or they will have to start the holding period over.
After treatment, growers will receive a permit that is valid for 10 days and allows for movement of the crop.
If a grower is near the quarantine zone and anticipates economic losses due to a long holding period should they fall under quarantine, they can voluntarily opt to join a pre-quarantine program. The pre-quarantine program is overseen by the county. Treatments applied during the pre-quarantine period count towards the holding period if a grower falls under quarantine later on. This reduces the amount of time that the crop is on hold. This is a proactive measure that is optional. Please direct questions about the pre-quarantine program to the pest exclusion program at the Ventura County's Agricultural Commissioner's Office (806-388-4222 ext. 7165) or UC ANR at hcohen@ucanr.edu
Quarantine regulations apply to most crops within the quarantine zone, but 'Hass' avocado has been excluded from the host list for Queensland Fruit Fly and Oriental Fruit Fly and is not subject to quarantine regulations
More complete information regarding the mitigations required for citrus movement may be found on the Citrus Grower/Grove Manager Information page: https://phpps.cdfa.ca.gov/PE/InteriorExclusion/pdf/acpgrowerinformation.pdf
- Author: Michael Hsu
QFF quarantine in LA, Ventura counties among seven fruit fly quarantines statewide
Residents in multiple Southern California and Northern California counties should not move homegrown fruits and vegetables from their properties to help contain several species of fruit fly that can destroy crops and impact the livelihoods of local farmers.
With sharing and gifting of food integral to the holiday season, the California Department of Food and Agriculture is reminding people to heed the seven active fruit fly quarantines aimed at controlling the Mediterranean fruit fly, Oriental fruit fly, Tau fly and Queensland fruit fly. The links below describe quarantine zone boundaries:
- Mediterranean fruit fly: Los Angeles County, Leimert Park Area
- Oriental fruit fly: San Bernardino and Riverside Counties, Redlands and Yucaipa Areas
- Oriental fruit fly: Sacramento County, Rancho Cordova Area
- Oriental fruit fly: Contra Costa County, Brentwood Area
- Oriental fruit fly: Santa Clara County, Santa Clara Area
- Tau fly: Los Angeles County – Stevenson Ranch, Valencia, Santa Clarita Areas
- Queensland fruit fly: Ventura and Los Angeles Counties, Thousand Oaks Area
People within these zones should consume or process (i.e., juice, freeze or cook) their homegrown fruits and vegetables at the place of origin and not move them off their property. Uneaten produce should be double-bagged in plastic bags and disposed of in the landfill bin – not compost or green waste.
Queensland fruit fly threatens California citrus, other crops
The Queensland fruit fly (Bactrocera tryoni) quarantine is the first of its kind in the U.S. Although QFF was first seen in California in 1985, the recent detection of two adult males triggered the unprecedented quarantine action by USDA's Animal and Plant Health Inspection Service and CDFA.
“This pest has earned a bad reputation for wreaking havoc on fruit production in Australia, where it is native,” said Hamutahl Cohen, University of California Cooperative Extension entomology advisor for Ventura County. “Adult flies lay their eggs in fruit, and the eggs hatch into larvae that then feed on the fruit, causing damage.”
And while females of other fruit fly species live for only two or three months, QFF females are unique in that they can live up to a year, according to Cohen.
“Once QFF populations take root, they're challenging to manage because females can each lay up to 100 eggs per day,” Cohen said.
In addition to being highly adaptable to a variety of environmental conditions, QFF has more than 170 host plants – including a wide range of California commodities such as citrus, grape, strawberry, fig, avocado, apricot, peach, cherry, nectarine, plum, pear, apple, tomato and sweet pepper.
The threat to citrus is especially concerning, as Southern California growers continue to grapple with the specter of spreading huanglongbing (HLB) disease, which kills citrus trees. Cohen said residents of citrus-growing regions can do their part to help their neighbors and local economy by respecting quarantine restrictions.
“Growers are already dealing with other invasive species like Asian citrus psyllid [vector of HLB pathogen], so we as homeowners need to prevent the spread of fruit flies to reduce the burden on them,” she explained.
While a spike this year in the detections of multiple fruit fly species was likely caused by a host of factors, Cohen speculates that increased post-pandemic travel is helping to move the flies. And with holiday travel in full swing, she said it's important to practice “Don't Pack a Pest” principles.
“Invasive species often hitchhike on fruits and vegetables brought into California by travelers – that's why we often first find invasive species in urban and suburban backyards, and not on farms,” Cohen said. “Travelers entering the U.S. can visit dontpackapest.com to learn about which products they can and cannot bring back with them.”
To report a suspected infestation of fruit fly larvae in homegrown produce, call the CDFA pest hotline at 1-800-491-1899. Growers with questions and concerns are urged to contact their local agricultural commissioner's office.
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