New Pests in the News
From the Davis Enterprise, April 23, 2009
If it ain't one thing, it's another.
I live just over the border from Davis in Solano County. A couple of years ago, a resident of nearby Dixon decided to bring a few pears home from Hawai'i. The Mediterranean fruit flies that escaped from those few fruit caused a quarantine all around the city of Dixon and the rural areas of Solano County up to the county line at Putah Creek.
No fruit or produce could be moved from gardens. Farmers had to implement strict, costly shipping procedures for walnuts and almonds. A small organic farm south of town lost thousands of dollars because the farmer couldn't sell his produce. The quarantine continued until traps monitored by the agricultural commissioner were medfly-free, which took two full growing seasons. Late last summer I could finally give away tomatoes and zucchini again.
My first thought when this all came down was "pears?! From Hawai'i?!" Not exactly the first thing I would have thought to sneak home from the tropical paradise. But regardless of the choice of fruit, this little transgression cost hundreds of thousands of dollars and affected the livelihoods of many people.
Don't bring fruit into California.
Quarantines are a constant concern for retail and wholesale nurseries. I spent over a decade on the board of directors of the state nursery association. Every meeting included updates on the latest pest threats to the agricultural and nursery industries of the state. Glassy-winged sharpshooter spreads a disease that kills grape vines. Red imported fire ants make outdoor living very uncomfortable. Sudden oak death kills native and introduced tree species. Each prompted various restrictions on the movement of nursery plants. So when Davis made the news April 1, 2009, with the finding of a little brown moth, I had a sense of deja vu.
Light Brown Apple Moth
Light Brown Apple moth is difficult even for trained entomologists to differentiate from many other small, brown moths. DNA testing is used to verify before quarantine measures are put in place. A single female can lay hundreds of eggs, and the larvae feed on foliage and fruit of many species. Photo courtesy of Greg Baker, South Australian Research and Development Institute.
Light Brown Apple Moth (LBAM) reproduces freely, laying eggs on many types of plants. Those eggs hatch into caterpillars that eat nearly everything. Feeding on over 1000 plant species, including 250 fruits and vegetables, the host range (list of plants they feed on) is so long that it is actually simpler to just list the plants LBAM doesn't eat. For example, it doesn't happen to eat olives, tomatoes, or walnuts. It does eat all the other major crop plants of Yolo County, including almonds, citrus, corn, grapes, stone fruits (apricots, cherries, nectarines, peaches, plums) and sunflowers. Not to mention many of the plants in your garden and landscape.
The pest was first confirmed in the Bay Area in 2007, California Department of Food and Agriculture (CDFA) attempted to control the pest via aerial applications of pheromones, but citizen complaints and lawsuits halted the spraying. The populations have thoroughly established and expanded rapidly. Agriculture Commissioners have traps set around neighboring counties and monitor them closely, and on April 1 a single LBAM was found in a trap between Mace and Richards boulevards, south of Interstate 80.
One moth does not make an infestation (unless she's pregnant...), and none has been found since. The hope is that the moth blew or hitchhiked in alone. Meanwhile, 100 traps are set within the square mile around it, and 25 per square mile in an area radiating out from there for a total of 300 traps. These are monitored weekly by employees of the USDA. Every nursery is already monitored by the county for LBAM and other pests. If another moth is found, there will be a quarantine on any plant-selling business within 1.5 miles of the find; each will have a compliance agreement with the ag commissioner, requiring a pest management program (read: spraying), and notices to customers.
As you can imagine, this is expensive. The biggest cost of these restrictions is implementing the quarantine itself: the trapping, the pest management, and the restrictions on movement and sale of farm produce and nursery stock. As Rich Landon, Agricultural Commissioner of Yolo County since 2001, told me, "the cost is significant and it is borne by the growers."
Light Brown Apple Moth is an innocuous-looking little pest. It looks very much like the moths you get in your pantry, and the caterpillars look like the larvae of many other types of moths. Landon commented that LBAM is "so nondescript that even when we found it we weren't sure" and had to have it confirmed by a state lab. So before you freak out and start sending household moths to the ag commissioner, you might want to check out the Light Brown Apple Moth Project page at the CDFA web site, www.cdfa.ca.gov.
Do quarantines work?
When the glassy-winged sharpshooter (GWSS) invaded Southern California and threatened Northern California's wine industry, those of us on the state board were frankly skeptical that the voluntary program could keep it south of the Tehachapis. The plan was that growers would inspect, spray, and certify their plants pest free. Then the shipment would be inspected at the receiving end as well before it could be sold.
Nurseries had a strong incentive to comply! Wine-producing counties were ready to block plants from entry. To this day every nursery receiving shipments from Southern California and certain other counties must offload the plants to a separate area and call the ag commissioner, and can't sell any of them until they're inspected and released. (Your tax dollars at work? No, it is mostly funded by fees paid by the nurseries.) Other than those found occasionally on shipments, no GWSS have been found in Yolo County. Says Landon, "the nursery industry has controlled it well." You're welcome.
So is this the only threat on the horizon?
Of course not. Far to the south a little bug called the Asian citrus psyllid has been found in a few locations in San Diego and Imperial counties. The psyllid (psyllids are related to aphids; the p is silent) spreads a bacterium that causes a disease called citrus greening, also known as huanglongbing (HLB) or yellow dragon disease, which has been devastating citrus trees in Asia and South America.
After a latent period in the tree of a coule of years, the disease causes mottled leaves, twig dieback, stunted growth, bitter and sour fruit, and eventually death of the tree. Citrus greening is established in southern Florida, and is a major threat to the citrus industry in that state. California is second only to Florida in the value of our citrus crop. The disease has also been found in Louisiana, and the psyllid (without the disease, yet) has been found in Texas, Georgia, Mississippi, South Carolina and Alabama, and Mexico.
What can you do?
It's mostly what NOT to do. If you happen to visit any of those places, please don't bring citrus fruit or foliage home with you. Don't bring plants of any kind from infested states or countries. Before you bring any plant into California, or move any plant within the state, ask about it. The county agricultural commissioner can tell you about any concerns or restrictions. Meanwhile, watch for media reports about new pest sightings in the Valley. The ag commissioner will alert nurseries and news media about measures necessary to prevent the spread of these new pests.
Maybe I should end on a more cheerful note.
Ladybug (ladybird beetle) larva look like little dragons, feed happily on aphids, and move very quickly -- too quickly to photograph! Shown here are four larvae as they are pupating, preparing to turn into the familiar ladybugs, of which three adults are also shown. If you have a resident population of ladybugs in your yard, your aphid problems may be over. If not, you can release some on cloudy days or in the evening. After they eat your aphids, they may stick around -- or they may fly off!
Every year about this time we get people wanting to know what the strange dragon-like creatures are that they've found on plants. Good? Bad? Should they spray? The larvae of ladybugs, more correctly known as ladybird beetles, look ferocious and very unlike the grownup bugs. But they are entirely beneficial, feeding even more voraciously on aphids than their parents. If you find these in your garden, you have established a resident population of ladybugs. That's good news for you, bad news for your aphids.
© 2009 Don Shor, Redwood Barn Nursery, Inc., 1607 Fifth Street, Davis, Ca 95616
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