First Release of Tamarixia radiata in California for the Biological Control of Asian Citrus Psyllid

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First Release of Tamarixia radiata in California for the Biological Control of Asian Citrus Psyllid

By Mark Hoddle | December 20, 2011

Provost and Executive Vice Chancellor of UC Riverside Dallas Rabenstein (left) and Mark Hoddle (right) made the first release of Tamarixia in Southern California.

At 11:00 am on the 20 December 2011, approximately 30-40 people assembled at the UC Riverside Biological Control Grove to participate in the first release in California of the Asian citrus psyllid natural enemy, Tamarixia radiata. Representatives from the University of California, California Department of Food and Agriculture, Citrus Research Board, and Citrus Pest and Disease Prevention Committee were in attendance. The event was covered by local media including Riverside’s Press Enterprise. After a brief introduction and description of the problem California faces with Asian citrus psyllid, and a quick review of the approximately two year process to reach this point, Mark Hoddle invited Provost and Executive Vice Chancellor Dallas Rabenstein to make the first release of Tamarixia in Southern California.

The Issue: In 2008, Asian citrus psyllid (ACP) was first found in California. This insect feeds on citrus and close relatives of citrus. The major problem with ACP is that is spreads a bacterium that causes a lethal disease in citrus known as Huanglongbing (HLB) . There is no cure for this disease. HLB is NOT in California.
ACP is widely established in LA County and pest populations are increasing and spreading in Riverside and San Bernardino Counties. This pest is almost exclusively restricted to backyard citrus. Spray programs to control ACP are difficult and expensive, and not every infested tree can be found and treated. Additional tools are needed for controlling ACP in California and biocontrol is one of these additional control options for ACP.

An adult Asian Citrus Psyllid on a citrus leaf.

The Biocontrol Program: ACP is native to Asia and the Punjab of Pakistan and India and this area is thought to be part of the native range where this insect evolved. People have accidently moved this pest and HLB around the world through the accidental movement of infested citrus plants.
Over the last two years Mark and Christina Hoddle (Department of Entomology, University of California, Riverside) have worked in Faisalabad Pakistan looking for natural enemies of ACP. Faisalabad Pakistan was chosen for this research effort because this part of Pakistan has a very good climate match (~70-75%) with the major citrus producing areas of California which will mean the natural enemies released in California will be pre-adapted to very hot dry summers and cold foggy winters.

An ACP Natural Enemy from Pakistan: One parasitoid found attacking ACP in the Punjab of Paksitan is Tamarixia radiata. This is a very small insect that kills ACP nymphs either by parasitizing them (i.e., females eggs laid underneath ACP nymphs and the parasitoid larvae burrow into the nymph to feed which kills the pest) or by host feeding (i.e., female parasitoids stab the nymph with their ovipositor, a tube that they use to lay eggs, and they feed on the body juices that leak from these wounds. This kills the nymph too.)

An adult female Tamarixia (left) and a dead Asian Citrus Psyllid nymph with an exit hole (right) from which an adult Tamarixia emerged after successfully parasitizing it.

Quarantine Studies: Safety tests conducted by Dr. Raju Pandey in Quarantine at UC Riverside clearly demonstrated that this parasitoid posed no undue risk to California’s environment, other species of insects, or humans. A 60 page Environment Assessment Report on Tamarixia that summarized the results of these studies was prepared by Mark Hoddle and Raju Pandey for review by USDA-APHIS. On 7 December 2012, APHIS issued a permit (P526P-11-04159) authorizing the release of Tamarixia from Quarantine for establishment in California for the biological control of ACP.

The Release Event: On 20 December 2011 at 11:00am, 12 glass vials containing 186 female Tamarixia and 95 male Tamarixia (total 281 parasitoids) were opened to release the parasitoids in the Biocontrol Grove at UC Riverside. The eight colonies in Quarantine from which these parasitoids were sourced for release were tested using DNA analyses to ensure that they were free of the bacterium that causes HLB. All tests were negative for HLB indicating that the parasitoids were free of this bacterium.
The Biocontrol Grove is a repository for natural enemies that have been imported for the biological control of citrus pests (e.g., scales, mealybugs, whiteflies, etc) in California over the last 50+ years. With the releases of Tamarixia in the Biocontrol Grove, one more natural enemy is being established here to combat an invasive pest that threatens California’s agricultural prosperity.

Expected Outcomes: This release of 281 Tamarixia is the first salvo against ACP in California. Over the next year or so it is anticipated that thousands of these parasitoids from Pakistan will be mass reared and released throughout LA, Riverside, and San Bernardino Counties and other areas as the pest continues to spread. Once Tamarixia establishes it will move by itself to find new populations of ACP to attack and kill. The parasitoids will have the ability to enter areas to kill ACP that may be difficult or impossible to reach for pesticide applications.

Tamarixia will *NOT* eradicate ACP from California but this natural enemy should reduce the populations of ACP in California. Every ACP killed by Tamarixia will be one less pest for homeowners and commercial citrus growers to worry about.

For More Information: These websites have more information on ACP and the work in Pakistan looking for natural enemies of ACP.

Topics: Asian Citrus Psyllid, Christina Hoddle, Mark Hoddle, News, Tamarixia radiata | 12 Comments »

12 Responses to “First Release of Tamarixia radiata in California for the Biological Control of Asian Citrus Psyllid”

  1. Elektronine cigarete Says:
    December 28th, 2011 at 11:16 am

    Small Asian citrus psyllid – big problems :). However, nice article (and nice pictures too).

  2. Hernán Camacho V Says:
    January 2nd, 2012 at 8:18 am

    Excellent effort. Congratulations! We are releasing Tamarixia radiata in Tico Frut Citrus Plantations in Costa Rica with very good results. I hope you have the best of success with your releases in California.

  3. Yves Uhoh Says:
    January 25th, 2012 at 4:39 pm

    Does the tamarixia radiata only eat the ACP? My concern is with the potential problems and unintended consequences of this release. What if the ACP starts to attack a beneficial, or something else? If you could comment on that I’d appreciate it.

  4. Mark Hoddle Says:
    January 26th, 2012 at 12:57 pm

    This is a very good question and one that is asked often about biological control agents.

    When we look for natural enemies of a pest like ACP and we find parasitoids, like Tamarixia, a key question we want to answer thoroughly is this: “What does it eat and reproduce on?” As biocontrol scientists we are most interested in finding natural enemies that have a very restricted diet, that is they are host specific and can’t eat or reproduce on a lot of different insects, attack plants, people, or pets.

    To answer this question, “how many different species of psyllid can Tamarixia eat?” we did a lot of testing in the Quarantine facility at UC Riverside. These tests were designed to determine when given a choice between different species of psyllids (California natives, some pest psyllids, and beneficial psyllids used for weed control) and the target pest ACP or no choice (it could only attack the one species of psyllid) what would Tamarixia do? Would it attack other species of psyllid and breed on them or not? What we found was that Tamarixia is extremely specific to the target pest ACP. When presented with other species of psyllid it did not recognize them as breeding hosts (either when non-targets were presented with no ACP or when presented with ACP).

    From these studies conducted over a 16 month period in Quarantine at UCR we prepared a 60 page Environment Assessment Report for USDA-APHIS and the CDFA (California Department of Food and Agriculture) to review and assess the safety of Tamarixia for release in California. The USDA-APHIS and CDFA concluded that the data from our tests indicated that Tamarixia poses no undue threat to the environment of California.

    Similar studies from Florida and Texas reached similar conclusions. Further, Tamarixia has been used as a natural enemy of ACP since the 1990’s in Florida and no unwanted environmental impacts have been documented. Similarly on Reunion Island, and in the Caribbean, Mexico, Central America, and parts of South America that now have ACP infestations Tamarixia is the key parasitoid attacking this pest. No adverse impacts of Tamarixia have been reported from these countries.

    Our (myself and my wife Christina) own field surveys in Pakistan over the last two years also indicate that Tamarixia is most commonly found attacking ACP in this country. This is important because Pakistan is probably the heart of the area where ACP and Tamarixia evolved. So it would appear that these two insects have had a long and very close evolutionary relationship.

    The weight of the evidence (from lab experiments in Quarantine and the large naturally-occurring field experiments in many different parts of the world) suggest that Tamarixia is very host specific and it is most interested in attacking and reproducing on ACP.

    Because Tamarixia is a specialist parasitoid with a very narrow host range, it will be very unlikley that it can “de-evolve” back into a generalist type natural enemy able to attack lots and lots of different insects. Most evolutionary biologist agree that specialists have evolved from generalists often by losing characters (or sometimes developing very unique traits) that gave them the ability to attack a lot of different prey.

    For a specialist to change back into a generalist would probably require a lot of major changes in biology, physiology, biochemistry, behavior, and ecology and many of these big changes would likely need to be happen together.

    Because Tamarixia will not eradicate ACP there will always be some hosts around for this parasitoid to attack so evolutionary pressure to under go radical changes to attack a lot of different insects seem unlikely.

    I hope this helps to address some of the concerns that you may have had about Tamarixia and its host range and how we investigated and determined its safety for California. We know that deliberately introducing a new species into a new location is a big responsibility and we have completed a lot of difficult lab experiments and field surveys to demonstrate the safety of Tamarixia.

  5. Conrad Says:
    March 28th, 2012 at 12:19 am

    Nice and valuable reading! Thanks for the info and I hope you have the best of success with your releases in California.

  6. Gabriel Rude Says:
    November 19th, 2012 at 12:10 pm

    When it this parasite become commercially available for insectaries to rear and produce?

  7. Mark Hoddle Says:
    November 19th, 2012 at 12:55 pm

    The Citrus Research Board is developing plans, in part with USDA-APHIS, to move the rearing of this ACP parasitoid at UC Riverside to a much larger scale. The involvement of commercial insectaries in southern California as part of this effort has been discussed, and the need for their participation has been acknowledged.

  8. Pest control services Says:
    December 18th, 2012 at 12:47 am

    Thats a really good info that you have provided and all the very best of success with your releases in California.

  9. Randy Black Says:
    April 29th, 2014 at 10:08 am

    Tremendous effort. Bravo! Your research establishing the extreme specialization of T. radiata to feed exclusively on ACP makes me wonder what the host-recognition mechanism is. If it’s a chemical signal, perhaps that could be used to select for the most aggressive parasitoids or even “train” an engineered sniffer sensor?

  10. Mark Hoddle Says:
    April 29th, 2014 at 11:05 am

    This is a very good question! Host specificity is likely a combination of a couple of things – olfaction and physical/chemical surface cues to assist with host recognition and then physiological and biochemical cues within the host. There is likely a hierarchy of cues that are employed by these parasitoids to determine whether or not the correct host is being attached.

  11. Ben Says:
    February 2nd, 2016 at 9:27 pm

    I’ve read some interesting stuff how in florida a couple of indigenous ladybeetles seem to be doing better job than the t. Radiata. Although in california I have read nothing but good news with the t. Radiata which is awesome and I know there is another hymenoptera that had been in quarantine and (for the life of me can’t remember the name of,the parasatoid) was curious to how that project was going.

  12. CISR Team Says:
    May 2nd, 2016 at 9:01 am

    Perhaps it was diaphorencyrtus aligarhensis? It is similar to tamarixia Radiata. http://cisr.ucr.edu/blog/uc-riverside/diaphorencyrtus-aligarhensis-release/


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