The End of California Citrus?

As small as an ant, the Asian citrus psylid is big trouble!

When I spotted state agriculture agents on our street I knew something was wrong. It turns out that a specimen of the dreaded Asian citrus psylid showed up in our neighborhood. The Asian citrus psylid is not a problem in itself, but carries an incurable bacterial disease called huanglongbing (HLB). HLB, first reported in Asia in 1919, renders citrus fruit inedible and eventually kills the tree. Parts of Africa, Asia and South America are infected with HLB and in some regions of Brazil the disease is so bad that they’ve given up growing citrus altogether. HLB is in Florida and is adding to a nightmarish collection of other diseases afflicting citrus in the Sunshine State. Now California growers are panicking with the appearance of the psylid.

So far the psylids found in California do not carry HLB. However, according to an article in the Journal of Plant Pathology (pdf), HLB inevitably follows the citrus psylid within a few years. In several ways HLB resembles Pierce’s disease which has killed most of my grape vines and basically made growing table or wine grapes in Southern California impossible without copious pesticide application. Both diseases are bacterial and both are spread by phloem sucking insects. The pesticides used to control the Asian Citrus Psyllid and the Glassy Winged Sharpshooter (the insect that spreads Pierce’s disease) are also the same, and include a ground application of imidacloprid, marketed under the brand name Merit and manufactured by Bayer Environmental Science. State agricultural officials that I spoke with at an informational meeting on Wednesday in Echo Park hope that applications of imidacloprid and pyrethroids will slow the progress of the psylid and, “buy some time”, as they put it, to come up with a strategy to deal with the possible appearance of HLB. California agriculture officials hope that their proactive approach combined with lessons learned from missteps in psylid control in Florida and the rest of the world will slow the progress of the insect and minimize the damage of an emergence of HLB in California.

Compliance with the residential pesticide application program is voluntary. State agriculture officials will knock on the doors of residents in three areas in Los Angeles where the psylid has appeared to ask for permission for a foliar application of pyrethroid and a ground application of imidacloprid to any citrus trees a homeowner might own.

While I understand the gravity of the situation–we really are looking at the possible end of citrus in California if HLB gets a foothold–the use of imidacloprid gives me cause for concern. Imidaclopred is highly toxic to honey bees and has been banned in several European countries for its likely connection to colony collapse disorder. When I told an employee of the Department of Pesticide Regulation at the meeting on Wednesday that people in my neighborhood keep bees he paused and said, “you’ve got a problem.” Another official said to me that our bees (and presumably other pollinators in the neighborhood) will be sacrificed for the greater good of preserving the state’s citrus industry.

As with Pierce’s disease the best long term solution to this problem will be to breed trees resistant to HLB. This is easier said than done as, unlike Pierce’s disease and grapes, no HLB resistant citrus cultivars have been found. It may be that the only way to breed for resistance soon enough to head off the HLB will be through the development of transgenes with antimicrobial properties. This approach is already being funded by the USDA and the citrus industry.

As a backyard gardener and rabble rousing blogger, I could lose a lot of sleep pondering all the thorny questions this crisis brings up. Are there situations where genetic modification is warranted, or do antimicrobial transgenes pose unintended consequences? Will localized applications of imidacloprid kill our pollinators in significant numbers or will strategic applications head off more widespread use later on if nothing is done? What are my responsibilities as a backyard gardener to large scale growers? Do the benefits of international trade outweigh the inevitable appearance of invasive species? Should we close the downtown flower markets and produce distribution warehouses where state entomologists suspect the psylids might have come from?

Rather than try to answer the unanswerable, I’m going back to two of my favorite books books that don’t have anything to do with plants. Nassim Nicholas Taleb’s The Black Swan: The Impact of the Highly Improbable, a meditation on the logical fallacies of economists and Seneca’s Letters from a Stoic have all the strategic wisdom a gardener needs. Seneca would say, do what is in your power to do and don’t worry about what you can’t fix. Taleb would advice always maximizing upside potential while minimizing exposure to the downside. My unsentimental conclusion: don’t try to grow citrus. If I had a mature tree I’d leave it in place and rip it out at the first sign of HLB. Despite the state’s offer to replace any HLB infected tree with a free citrus tree I wouldn’t take them up on the offer. In our case we have three small, immature citrus trees that are already chewed up by citrus leafminers. I’m pondering pulling them up and replacing them with fruit trees unrelated to citrus. This follows our stoic, get tough policy in the garden. Planting a tree entails a considerable investment in time. It can take years to get fruit. Why not plant pomegranate instead and let other people worry about citrus diseases? If a pomegranate disease shows up, rip it up and plant something else. Following this approach will eliminate habitat for the psylid and negate the need for pesticides.

Orange v. Tuna ¿Quien es Más Macho?

The first consideration with any domestic plant or animal should be choosing species with robust immune systems and then following that up with an objective selection process. This is an approach that mimics one of the fundamental laws of evolution: survival of the fittest. True, there is often a trade off between the flavor and yield of a fruit and strength of its natural defenses. Oranges are juicier and easier to peal than the spiny and seed filled fruit of the prickly pear cactus. But the long term odds of having a reliable supply of prickly pear fruit are a lot higher than a steady flow of orange juice. I may get a few spines in my fingers, but it will be the citrus farmers who will be losing sleep. As Seneca says, “If you shape your life according to nature, you will never be poor; if according to people’s opinions, you will never be rich.”

View a video on how to recognize Asian citrus psylids here.

Leave a comment


  1. What I’d like to see is a phage that is temperate in the psylid’s normal gut flora, but lethal to HLB bacteria.

    Forget tree genes. Virus genes are both more diverse to begin with, and easier to modify. Phages can be bred without manipulation much, much faster than transgenic fruit can be developed.

  2. There’s a quarantine on all citrus trees in LA county. I tried to order a bunch of citrus for a project I was doing and our supplier said “it’s not cost effective for us to sell citrus under the quarantine”

  3. Please clarify: one doesn’t HAVE to let the inspectors examine one’s property? Or, if they do find something, does one HAVE to let them spray? I’m with you—I’ll dig up my beloved lemon tree before I let them exterminate my bees (which will probably happen anyway since they will be spraying somewhere in our neighborhood, I’m sure.) Sigh.
    btw, do you know if a loquat is considered a citrus?

  4. Costa Rica used to grow the world’s chocolate. Now they can’t grow a single tree that isn’t covered with some kind of fungal blight.

    Fascinating, disturbing, this wild world we live in…

  5. Sue–you don’t have to let them on the property and they can’t spray without your permission. I’d keep your lemon tree for now, I just wouldn’t plant new citrus. And no, loquat is not a citrus, it’s in the rose family. Let’s keep our fingers crossed about the bees.

  6. It depends on where you live. If you’re in Southern California, we’ve had good luck with figs, pomegranates and pineapple guava. All of the aforementioned tolerate so-so soil and can put up with heat and dry spells.

  7. medlars do well here. I did a post on medlars “forgotten fruits” a while back (I guess when i was still active). I’m trying to single handedly bring back the medlar. wish me luck

  8. Thanks for your response – Sorry – I forgot you have readers from all over! I live in the SF Valley of LA. We have planted a fig, and will look into pomegranates and pineapple guava. Have you tried loquats? They seem to do well here, I’m just not sure what I’d do with that fruit.

  9. Anonymous:

    We don’t have a loquat ourselves, but our neighborhood is full of them. They seem to do very well here in central LA with little care. Most of the ones we forage from are scrappy little street trees that bear abundantly.

    The fruit is tasty, but as far as I can determine, it is best eaten straight off the tree. It spoils very quickly once picked, and doesn’t lend itself very well to drying,jam making, etc.

    If we had a still, I might try to make some loquat hooch. Now there’s a noble goal!

    If anyone knows how to do anything with them, let us know–because if we had good cause, we could forage them by the bucketful.

  10. I read about the psylids a couple weeks ago, and am concerned about my tree more for sentimental reasons. My parent’s orange tree was one of the first orange trees planted when the houses on our street were built in the early 1930’s, so it’s a fairly large and beautiful tree. To hear that they would mandate spraying is just awful… but I imagine necessary until they find other means to control the psylid, unless we decide to take it out and plant something else (which will be a whole other can of worms considering the money and man power needed to take out the whole tree and the roots too?) About a month ago the Orkin man was soliciting, and proudly told me 40 of my neighbors were spraying, and that the spiders and other insects might behave strangely (because they’re irritated as hell over residual pesticides clinging to their body if they managed to escape). When I tend my front yard garden, I see so many honey bees and countless native bees and other critters, it’s just too depressing to think of how easily and gladly people will spray to wipe these out, out of convenience. But enough of that tangent. Hello, if you spray the citrus trees and it kills honeybees, what’s going to pollinate the citrus trees?? Even if we cut down our tree, West Los Angeles has hundreds if not thousands of citrus growing in the neighborhoods- biking down a street, it’s impossible not to see at least one citrus tree growing on someone’s property. And you know what, not everyone is going to opt to cut down their tree.. what can we do about the bees then? :

  11. my neighbor makes a loquat jam…I have no clue how she does it, there’s just always been a jar in the fridge when I come home from school. Even worse, the loquats come from our yard! I’ve got to get over there and figure this out.

    as far as the phage comment, it’s mind boggling to think of the ins and outs of viral pesticides. though bayer and friends have a vested interest to keep alternatives from undercutting their products, so I don’t predict seeing anything effective anytime soon.

  12. I have one Medlar tree at my house in a pot. (in Pomona) they don’t actually need any chill to fruit, (I just got it a year ago and I wanted to see how they do here, and the report is, they do quite fine) although they need chill or a long storage to become palatable (they need to be bletted), so once they fruit and ripen you can just stick em in the freezer for a couple of days and then take them out. Or just keep them for a while and let them blet naturally.

  13. >ayer and friends have a vested interest to keep alternatives from undercutting their products

    They are a big tree. We are a small axe.

    Microbiology takes some capital equipment and expertise, but it is not “ig science.” Microsoft has not prevented the development of Linux, no matter how much vested interest there was.

  14. The truth is, we the 90% actually have more power over the 10%(the corporate giants), it is time we (the sleeping giants) step up to the plate, pull together and do something about this kind of thing, hence make sure research and funding (our tax dollars) goes to alternative methods rather then destroying whole ecosystems with pesticides whilst lining the pockets of the 10%.

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