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Carey Engages Audience in California's Fruit Fly Crisis
If you missed UC Davis distinguished professor James R. Carey's well-attended seminar on...
UC Davis distinguished professor James R. Carey presented a seminar on "California's Fruit Fly Invasion: A 70-Year Struggle Nears Critical Mass" on June 3 in Briggs Hall, UC Davis campus, and on Zoom. (Photo by UC Davis distinguished professor Walter Leal)
First-ever Queensland fruit fly quarantine restricts moving homegrown produce
QFF quarantine in LA, Ventura counties among seven fruit fly quarantines statewide Residents in...
First-ever Queensland fruit fly quarantine restricts moving homegrown produce
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.
Headwaters
I have the privilege of engaging California's communities with the aspiration of safeguarding the sustenance and well-being that its oak-woodland watersheds and the people that are a part of them provide. This millennia-long integrated relationship of humans and land has parallel histories in other Mediterranean parts of the world. The following blog is the first of occasional installments about working Mediterranean landscapes in California and around the globe. Combined they will explore the concepts of watershed functions, working landscapes and Mediterranean climate, vegetation and management. Join me in experiencing these settings, growing our appreciation for the integrated nature of these landscapes and people, and gaining understanding and tools for our tenure as stewards. - David Lewis, director, UC Cooperative Extension, Marin County
I am standing where stream flow begins, in a nameless tributary of the Russian River to the east of Hopland, Calif. This particular spot and location has been a grazing livestock ranch, primarily sheep, going back more than 100 years (learn more). This is one of thousands of spots in a watershed where water comes to the surface, joins in a channel and starts its path downstream. Many of us have stood at a confluence of two rivers or an estuary where a watershed's outfall meets an ocean. These locations are the stream's or river's end, their terminus. Where I am standing, is the headwaters of a stream system, where water is initially released and visible as a thin, shallow bouncing band.
Watersheds collect, store, and transport water. The transport function is performed by streams and rivers. These are dynamic, pervious channel networks each with a beginning and an end. At any part of the network, the channel is that lowest point in the landscape, stretching from one stream bank to the other, and generally widening in the downstream direction, until the stream mouth empties into another water body.
At the other end of a network is the channel head, where the channel begins. This is where I am standing. Channel heads are found in small, intimate folds in the landscape. These depressions are referred to by many names — draws, bowls, hollows — the place in hills where the slopes become shallow and coalesce.
Like an amphitheater, the surrounding hillslopes rise around me. Reaching out at shoulder height, I can almost touch these slopes. The mixed oak woodland and interspersed grasslands are in attendance across these slopes. Ghost pines, live oaks, black oaks and madrones, among other trees, make their stand interspersed with annual and perennial grasses blanketing the ground. This mosaic of vegetation is hosted and sustained by the complex mix of marine sediments that have been pushed up, forming these hills, and erosion carving the stream channel. Below the surface are soils one to three feet deep that have developed from the underlying geology.
It's March 3, 2019, and on the cusp of spring. Between the light breezes, the stream water sings its way downstream. I think back to the intense storms that moved across this part of California the week before and the resulting floods in the lower portion of the Russian River. Those and earlier winter storms soaked into the soil until the soil reached its capacity to hold water. Once the soils were primed, water was released to the channel network. That water is still being released now, days later, and will be for several more months into May or even June. Rainfall for this area and most of California has been substantial, matching amounts not seen since 1983, and definitively ending the nearly five-year drought. This contrast in extremes is the norm for California, meaning the next drought or next flood is only a year away.
Downstream the Russian River is perennial, flowing year-round. But here at the channel head, flow is intermittent on an annual cycle. Rains begin in the fall, with headwater surface flows starting in late fall or early winter, once soils are saturated. This wetting up process reverses in the spring, until the channel head is dry.
At some point this year flow in the headwaters will stop. Saturated soils releasing water laterally below the ground surface, will gradually release less and less water to the channel. Trees and grasses will demand more and more water as they leaf out and grow. As soils pores empty of free water, the remaining moisture is held more tightly to soil particles and plant root surfaces through a physical tension. Eventually the channel head will run dry.
While you may not have the opportunity to visit a channel head and experience the place where stream flow starts and stops each year, you are often closer to one than you think. Driving a rural road or hiking in a favorite park or open space will invariably find you crossing one of these unnamed headwater streams. As you do, give a look upstream, from where the water going past you has come. Up the channel into the bowl is one of the channel heads and headwaters for the watershed you are in.
I don't know when I will get to this channel head again. However, this place where surface flow is initiated will be close in my mind, particularly, as I visit the confluences and estuary of the Russian River, during the wet and dry periods and high and low rainfall years to come.
To learn more about these specific watersheds and research conducted in them this article is suggested. If interested in learning how stream flow is generated in California oak woodland watersheds you may want to read this article.
The Medfly 'Through the Decades': Tune in to Hear Professor Carey on July 3
Remember when scientists first detected the Mediterranean fruit fly in California? It was the...
Distinguished Professor James R. Carey is known for his outstanding research, outreach and advocacy program involving invasion biology, specifically the Mediterranean Fruit Fly (medfly) and the Light Brown Apple Moth (LBAM). (Photo by Kathy Keatley Garvey)
