Asian Citrus Psyllid

Tracking Down Asian Citrus Psyllid in Pakistan

Anonymous — Mon, 20 Jan 2020 07:27:04 +0000

Tracking Down Asian Citrus Psyllid in Pakistan Anonymous (not verified) Sun, 01/19/2020 - 23:27 More Blog Posts CISR Team September 28, 2010

The Hunt for Natural Enemies has Begun

Mark S. Hoddle, University of California, Riverside

Asian citrus psyllid (ACP), Diaphornia citri, is considered to be one of the world’s most serious threats to economic citrus production because it vectors a bacteria, Candidatus Liberibacter asiaticus, that causes Huanglongbing (HLB) (also known as citrus greening), a disease that is lethal to most varieties of citrus. In countries where this psyllid-bacteria combination have successfully invaded, citrus production has dropped markedly because trees go into decline losing vigor, leaves drop from trees and the canopy becomes thin, and developing fruit tends to become small, misshapen, and bitter.

In September 2008, ACP was found in southern California and it is thought that this insect entered California from Mexico where this insect and HLB are both present. Currently, HLB is not known from California.

Collecting Asian citrus psyllid in the Punjab of Pakistan with Faculty and Students from the University of Agriculture at Faisalabad. Even the Elite Punjabi Commando unit was curious about our surveys and joked with us as we moved between field sites.

In an attempt to manage ACP in California, entomologists at the University of California Riverside have been working at the University of Agriculture in Faisalabad in Pakistan to better understand the impacts natural enemies have on controlling ACP in the Punjab region of Pakistan. The reason this area was selected for investigation is because the Punjab region of Pakistan and India may be the area of origin where ACP and HLB evolved. The reason for this assumption is that the first study on ACP was published by two “Imperial Entomologists” Mohammad Husain and Dina Nath who studied ACP attacking citrus primarily in the Punjab region of Pakistan. Their research entitled “The Citrus Psylla (Diaphorina citri Kuw.) Psyllidae: Homoptera” was published in 1927. In this article, Husain and Nath state that nine species of parasitoid attack ACP in the Punjab.

Gathering insects from citrus plants in the Punjab of Pakistan generates an immense amount of curiosity. Kids in particular were also super-curious about what we doing, where we had come from, and why we had come to Pakistan. People in the Punjab of Pakistan are incredibly courteous, polite, and generous. This was even more remarkable given that it was Ramadan when we were visiting and that the Punjab had experienced the most devastating floods in living memory. Our experiences in Pakistan ran completely against the prevailing western media views we are exposed to on a daily basis about this country.

What is very curious about Husain and Nath’s work is that today, we know of only two species of parasitoid that attack ACP, not nine species. This lack of information on parasitoids associated with ACP in the Punjab of Pakistan raises a very important question: What are these species of parasitoid attacking ACP in the Punjab of Pakistan?

To get a better handle on the ACP-natural enemy situation in Pakistan, Mark and Christina Hoddle visited the University of Agriculture in Faisalabad in Pakistan in September 2010. This trip was supported by funds provided to the California Department of Food and Agriculture (CDFA) by the Citrus Health Response Program (CHRP).

This visit was extremely useful as it provided an opportunity to visit the same citrus production areas that Husain and Nath worked in during the early 1920’s. Excellent working relations were forged with faculty at the University of Agriculture in Faisalabad, and the infrastructure exists in Pakistan for developing a classical biocontrol program for ACP in California. Plans are being developed for 2011 to take advantage of the momentum this visit to Pakistan has created.

Farmers, the Punjabi Elite Commandos (assigned to escort us and protect us at field sites), Students from the University of Agriculture at Faisalabad, and Mark Hoddle looking for Asian citrus psyllid in Kinnow orchards. Kinnow is a type of mandarin developed at the University of California Riverside by plant breeder H.B. Frost in 1935 that has flourished in the Punjab of Pakistan and India.

Asian Citrus Psyllid, Invasive Species, Mark Hoddle

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Asian Citrus Psyllid

Invasive Species

Mark Hoddle

Tracking Down Asian Citrus Psyllid in Pakistan

Anonymous — Mon, 20 Jan 2020 02:29:08 +0000

Tracking Down Asian Citrus Psyllid in Pakistan Anonymous (not verified) Sun, 01/19/2020 - 18:29 More Blog Posts CISR Team October 28, 2010

The Hunt for Natural Enemies has Begun

Mark S. Hoddle, University of California, Riverside

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Asian Citrus Psyllid

Invasive Species

Mark Hoddle

Hunting for Natural Enemies of Asian Citrus Psyllid in Pakistan

Anonymous — Mon, 20 Jan 2020 02:03:46 +0000

Hunting for Natural Enemies of Asian Citrus Psyllid in Pakistan Anonymous (not verified) Sun, 01/19/2020 - 18:03 More Blog Posts CISR Team November 08, 2011

Asian citrus psyllid (ACP) was found in California in late 2008 in San Diego and Imperial Counties. This invasive pest sucks sap from citrus and is a major concern for California because when feeds ACP inject into trees bacteria that cause a lethal disease of citrus known as huanglongbing (HLB). This plant disease is incurable, is restricted to citrus, and poses zero (i.e., no) risk to humans. HLB is also known as yellow shoot disease or citrus greening.

This ACP-HLB combination has been particularly devastating following its arrival in major citrus producing areas. In Florida for example, 60,000 acres of citrus, about 10% of commercial production, was taken out by HLB within 4-5 years of the first detection of the disease. At the time this blog was written (November 2011), HLB had not been detected in California. However, many suspect that the disease is present in California, and could be residing undetected in backyard citrus, possibly in plants that were smuggled into the state from areas where HLB is present (e.g., Asia, Mexico, or Florida).

Since 2008, large ACP populations have developed in Los Angeles (LA), Riverside, and San Bernardino, Counties. The vast majority of infestations found by the California Department of Food and Agriculture’s (CDFA) monitoring program have been detected in urban areas. Citrus is a very popular backyard fruit tree and homeowners grow a large variety of different citrus including oranges, mandarins, lemons, limes, kumquats, and grapefruit. It has been estimated that there is more citrus growing in people’s gardens than there is in all of California’s commercial citrus production areas combined. Surveys by UC Riverside scientists working on ACP in LA have found that ACP is encountered most often on lemons and limes, and populations can reach very high levels on Mexican limes, which appear to be a highly favored host.

Containing ACP in urban areas is a major challenge that the CDFA and Citrus Research Board (CRB) have jointly undertaken. The management plan involves treatments of residential trees that have ACP and neighboring trees within a prescribed distance of the infested tree that triggered treatments. Pesticide applications may include foliar sprays to kill ACP eggs, nymphs, and adults, and soil drenches with approved systemic insecticides that move inside the plant killing ACP when they suck sap. Finding and treating ACP infested citrus is a difficult and expensive task, and some homeowners don’t like the idea of pesticides being applied to citrus in their gardens.

UC Riverside with support from CDFA, CRB, and the Citrus Health Response Program (CHRP) has initiated a classical biological control program for ACP. This approach to ACP control involves finding natural enemies of the pest in its native range. Most scientists who work on psyllids, the group to which ACP belongs, agree that this insect is probably native to parts of central and southern Asia and has been moved unintentionally on citrus into areas where it is not native. Once in these new areas, with lots of citrus to feed on, favorable year round climates, and a lack of specialist natural enemies, ACP populations increase and spread rapidly.

Part of the native range of ACP is the Indian subcontinent, and the very first study on ACP was published by two scientists Mohammad Hussain and Dina Nath in 1927 . They conducted their research on this citrus pest in the Punjab region of modern day Pakistan and India where is it was associated with declines in lemons and oranges. Hussain and Nath (1927) also reported that there were nine species of parasitoid attacking the nymphs of ACP and that parasitism of this pest could sometimes exceed 90-95% at certain times of the year. One species of parasitoid, Tamarixia radiata, an eulophid that preferentially attacks the fourth and fifth instars of ACP was reared described from specimens that emerged from ACP infesting lemon leaves in Lyallpur in 1922!! This parasitoid has been used in Florida, Texas, Mexico, the Caribbean, Central and South America for biological control of ACP.

The Punjab has a very good climatic match (about 70% similar) with the major citrus producing areas in the Central Valley of California. Biological control theory suggests that climates that are similar in the pest’s region of origin and the intended receiving range for natural enemies is important because it increases the likelihood that biological control agents will be well adapted to the climatic conditions in the area into which they could be introduced. There are basically three seasons in the Punjab; cool and foggy (October – February), hot (March-June), baking hot and humid (monsoon season July – September).

UAF Pakistan

The Central Valley is characterized by very hot dry summers and cold foggy winters (Tule fog). It is anticipated that parasitoids of ACP sourced from the Punjab of Pakistan will be well adapted to California’s citrus growing areas.

Agri Entomology

Foreign exploration for natural enemies of ACP in the Punjab of Pakistan was initiated with a trip over the period 28 August 2010 to 5 September 2011 to assess the potential for collaboration with scientists in the Department of Agri-Entomology at the University of Agriculture Faisalabad (UAF) (Faisalabad was formerly known as Lyallpur). It was quickly determined that UAF would be an excellent base for this project because it had research plots of citrus infested with ACP that were not treated with insecticides, UAF is closely positioned to Sargodha and Toba Tek Singh important commercial citrus production areas in the Punjab, and the Vice Chancellor of UAF, Dr. Iqrar Khan, a MS and Ph.D. graduate from UC Riverside (supervised by Dr. Mikeal Roose) and world leader in HLB research was extremely enthusiastic about developing a joint project between UAF and UC Riverside.

Mark and Christina Hoddle with VC Khan

Zaman taking field data

A four week trip to Pakistan over the period 11 March 2011 to 10 April 2011, resulted in the setting up of two research plots in Square 9 and PARS, both of which are UAF citrus research areas. In these two plots ACP and natural enemy population dynamics and flush growth patterns are being studied weekly on two different types of citrus, kinnow and sweet orange. Kinnow, a type of mandarin bred at UC Riverside by H.B. Frost in 1935 and introduced to UAF in 1940 and the first tree was planted in Square 9 one of our current study sites! Kinnow accounts for about 85% of citrus produced in the Punjab and it is an export crop for Pakistan. A Masters Student in Agri-Entomology, Mr. Shouket Zaman Khan was trained to do this work, and he is supervised by Dr. Mohammed Jalal Arif. At the end of this period, 80 Tamarixia radiata (24 males and 56 females) and 70 Diaphorencyrtus aligharhensis (25 males and 45 females) were returned to Quarantine at UC Riverside and used to establish colonies. All living material for this project is moved under USDA-APHIS permit and is cleared at LAX by Homeland Security Personnel before being moved to the Quarantine Facility at UCR.

Dr. Mohammad Jalal Arif working three phones

The third trip to Pakistan to look for ACP natural enemies was conducted over the period 6 June 2011 to 13 June 2011. This trip was very successful and 406 T. radiata (151 males and 255 females) and 25 D. aligarhensis (21 males and 4 females) were returned to UCR’s Quarantine facility.

The fourth collecting trip to Pakistan was completed over 28 October to 4 November 2011. From this collecting trip about 800 T. radiata and approximately 30 D. aligarhensis were brought back to UC Riverside. From all of these collections, just two parasitoids of ACP have been collected, T. radiata and D. aligarhensis. Consequently, we are questioning the validity of Husain and Nath’s (1927) claim that ACP nymphs were attacked by nine different species of parasitoid. Based on our experiences with collecting and rearing large numbers of specimens from Pakistan and from three different time periods it seems unlikely that the parasitoid fauna associated with this pest is diverse.

Shipments of natural enemies carried from Pakistan to UCR are processed in a receiving room in Quarantine. During this initial inspection phase, shipments are checked for accidental contaminants which are eliminated and destroyed immediately. Colonies of these natural enemies are set up in Quarantine at UC Riverside and are maintained as isocage lines to preserve genetic diversity. Maintaining colonies of ACP and its natural enemies in Quarantine is very difficult, time consuming, and requires meticulous attention to detail. Colonies of ACP and natural enemies are double caged, kept in secure rooms that are within secure rooms, and workers must wear coveralls which are removed in a designated changing room once work in the colonies is finished for the day.

T. radiata and D. aligarhensis are undergoing safety testing to ensure that they will pose no undue risk to the environment in California. Release of T. radiata for biological control of ACP in California is anticipated for Spring 2012 once the Environment Assessment Report has been reviewed and approved by USDA-APHIS.

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

Anonymous — Mon, 20 Jan 2020 02:01:15 +0000

First Release of Tamarixia radiata in California for the Biological Control of Asian Citrus Psyllid Anonymous (not verified) Sun, 01/19/2020 - 18:01 More Blog Posts 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, Tamarixiaradiata. 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 Tamarixiaestablishes 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.
http://cisr.ucr.edu/asian_citrus_psyllid.html
http://cisr.ucr.edu/citrus_greening.html
http://cisr.ucr.edu/blog/psyllids/hunting-for-natural-enemies-of-asian-citrus-psyllid-in-pakistan/

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Tamarixia radiata release video

Anonymous — Mon, 20 Jan 2020 01:53:31 +0000

Tamarixia radiata release video Anonymous (not verified) Sun, 01/19/2020 - 17:53 More Blog Posts CISR Team January 12, 2012

Christina Hoddle explains the release of Tamarixia radiata at UC Riverside. Video recorded on December 20, 2011 at University California Riverside.

For more information about Tamarixia radiata and Asian Citrus Psyllid, visit the CISR website: http://cisr.ucr.edu/asian_citrus_psyllid.html

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Huanglongbing Detected in Hacienda Heights, Los Angeles County

Anonymous — Mon, 20 Jan 2020 01:50:18 +0000

Huanglongbing Detected in Hacienda Heights, Los Angeles County Anonymous (not verified) Sun, 01/19/2020 - 17:50 More Blog Posts Mark Hoddle April 13, 2012

The Situation: On Thursday April 5 2012, after about a week of testing, the California Department of Food and Agriculture (CDFA) removed a pumelo tree with a lemon graft from Hacienda Heights in Los Angeles County after the tree and an Asian citrus psyllidfound on the tree both tested positive for a lethal citrus disease, Huanglongbing(pronounced Wong-Long-Bing [HLB]). HLB is caused by a bacterium, and HLB-causing bacteria kill citrus by affecting the food transportation systems of infected trees. There is no known cure for the disease, and the HLB-bacterium does not pose a threat to humans, pets, or other plants.

Asian Citrus Psyllid

The Problem: Huanglongbing, also known as yellow shoot disease, yellow dragon disease (these are English translations from the Chinese Huanglongbing indicating that the leaves of infected citrus appear an irregular mottled yellow color) or citrus greening (because fruit don’t ripen properly and remain green in areas) is spread from tree-to-tree by the Asian citrus psyllid (ACP), This small insect acts as a flying syringe carrying bacteria in its needle-like mouthparts and when infected psyllids feed on citrus they inject bacteria into trees. The disease can also spread by grafting infected branches onto healthy trees. The possibility that an infected branch was brought into California and used for a graft is being investigated.

Infected trees typically die within 5-8 years after being infected, but disease symptoms may take as long as 2 years to become obvious. This long latency period provides ample time and opportunities for ACP to visit infected plants, feed on them, acquire the bacteria and fly onto healthy trees to feed which puts these trees at risk of becoming infected with bacteria.

HLB has been a particularly devastating disease problem in Florida. In 2005, HLB was first detected and it was estimated that 10% or 60,000 acres of citrus was destroyed by HLB by 2009, just four years after the first find. This reduction of citrus acreage in Florida corresponded with an estimated loss of 6,600 jobs, $1.3 billion in lost revenues to growers, and $3.6 billion in lost economic activity associated with the citrus industry in Florida.

The commercial citrus industry is worth about $1.2 billion in California and about 300,000 acres are farmed.

Where are ACP and HLB in the USA? ACP and HLB are present in Florida, Texas, Louisiana, Georgia, and South Carolina. ACP is present in Arizona, Mississippi, and Alabama, but HLB has not yet been found. In California, ACP was first found in San Diego and Imperial Counties in 2008. Since this initial detection ACP has been found in Ventura, Orange, Santa Barbara, Los Angeles, Riverside, and San Bernardino Counties. ACP populations at this time are heaviest in Los Angeles County.

The quarantine for HLB in Los Angeles and Orange Counties

The Response: On April 5 2012, the CDFA held an open house meeting at Industry Hills Expo Center in the City of Industry. The purpose of the meeting was to provide the public with information on HLB and ACP and to respond to requests to examine citrus with disease symptoms that look suspiciously like HLB. Additionally, all citrus within an 800 meter (about 2,400 feet) radius of the infected tree have been treated with insecticides by the CDFA to kill any Asian citrus psyllids that may be carrying bacteria that cause HLB. A 93 square mile quarantine has been established in Hacienda Heights in Los Angeles County and part of northern Orange County. This quarantine prohibits the movement of all citrus nursery stock out of this area in case they are infected with HLB and these plants, if infected, could start new disease infestations in different areas of California. Any fruit from residential properties must not be moved to other areas in case ACP or HLB accidentally hitch-hike into new areas on this fruit.

A description of the Quarantine has been prepared by CDFA and maps of the Quarantine Zone are available.

What is the Future for Citrus in California? Following the find of HLB in Hacienda Heights there has been concern that a massive citrus die off in gardens is now imminent. This is unlikely because surveys have failed so far to find more than one tree infected with HLB. Further, it is unlikely that trees dying from HLB be initially widespread, it is probable that if there are other HLB infected trees in California, they are uncommon and widespread. The difficult problem facing the CDFA and USDA is finding these infected trees (should they exist) and eradicating them before ACP finds them, feeds, acquires HLB bacteria, and spreads them to healthy citrus. Because the disease is slow in killing trees, the loss of trees will be slow, and probably patchily distributed in the early stages of the spread.

What Can you Do to Help? The CDFA has set up a Pest Hotline 1-800-491-1899 and a Report-a-Pest website http://www.cdfa.ca.gov/plant/reportapest/ to help in the fight against invasive species coming into California.

Recent News Articles
Los Angeles Times: Gardeners’ Common Bond May Have Introduced Deadly Disease.
Los Angeles Times: San Gabriel Valley Homeowners Swarm to Meeting about Citrus Disease

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Has the Asian Citrus Psyllid Parasitoid, Tamarixia radiata, Established in California?

Anonymous — Mon, 20 Jan 2020 01:47:41 +0000

Has the Asian Citrus Psyllid Parasitoid, Tamarixia radiata, Established in California? Anonymous (not verified) Sun, 01/19/2020 - 17:47 More Blog Posts Mark Hoddle July 19, 2012

Tamarixia radiata (female)

The Problem: Tamarixia radiata, a tiny parasitic wasp has been imported into California from the Punjab of Pakistan to attack nymphs of Asian citrus psyllid (ACP), a serious citrus pest that has established wide spread populations in the counties of Los Angeles, San Bernardino, and Riverside (significantly smaller populations are known in Imperial and San Diego Counties too). Releases of Tamarixia commenced in December 2011 after USDA-APHIS cleared this natural enemy for release from the Quarantine Facility at the University of California Riverside. Since these initial releases in December, approximately 8,500 parasitoids have been released at about 50 different sites in Southern California by July 2012.

The Biocontrol Release Program: Parasitoid releases have been made in the cities of Azusa, Bell Gardens, Chino, Duarte, Fontana, Los Angeles, Mira Loma, Montclair, Ontario, Pico Rivera, Pomona, Rialto, Riverside, San Bernardino and Whittier. In these areas, citrus in residential gardens with ACP infestations were selected for parasitoid releases. Ideally release sites had lemons or limes, and other types of citrus too (e.g., oranges or grapefruit.) Lemons and limes are good hosts for ACP because they tend to produce a lot of flush growth that is favored by ACP females for egg laying, and lemons in particular, tend to produce flush growth more frequently when compared to other types of citrus (e.g., oranges.)

A mixture of different citrus types in gardens is desirable for a release site because it increases the possibility that there will be flush present on different citrus types at different times of the year that will be available for ACP can infest. We’ve also noticed that semi-regular pruning of citrus, good fertilization, and decent watering schedules can also help garden citrus produce strong flush.

Tamarixia Recoveries: Parasitoids have been recovered at about 4-6 release sites in Azusa and Bell Gardens, and some of these sites have not received parasitoid releases for 2-3 months suggesting that Tamarixia has likely established and is breeding on its own (the life cycle of the parasitoid is about 12-14 days depending on the temperature). DNA analyses suggest that the parasitoids that have been recovered from release sites have a unique genetic signature that is very similar to the parasitoids imported from Pakistan for the biological control of ACP in southern California. This result tentatively suggests that the parasitoids recovered from release sites are most likely those that were mass reared and released by the

Tamarixia radiata parasitizing an Asian citrus psyllid nymph in Bell Gardens Los Angeles County

University of California Riverside. Further, at one site in Azusa, it appears that Tamarixia has self-dispersed about 65 m from where it was released on citrus and it established new populations on ACP infested curry plants (curry plants are really good hosts for ACP too.) Additionally, the genetic signal from captured parasitoids is reasonably diverse which suggests that the foreign exploration, rearing, and release program at UCR has preserved a lot of genetic variation which could be very important for local adaptation by parasitoids to citrus growing areas from the coast to the inland valleys.

How Does Tamarixia Kill ACP? Tamarixia can kill ACP nymphs in two different ways. First is parasitism, and in this instance a female parasitoid lays an egg underneath a fourth or fifth instar (instar refers to the developmental stage of the nymph, so a fifth instar is the fifth nymphal stage before the nymph becomes an adult) nymph. These larger nymphs are most preferred by Tamarixia for parasitism. When the egg hatches, the parasitoid larva begins to feed on the under surface of the ACP nymph. Eventually the Tamarixia larva will completely excavate the body cavity of the ACP nymph, and it will pupate inside the empty shell of its host. Often you will see beige colored silk strands radiating out from the edge of a mummified ACP nymph. The parasitoid larva spins this silk to hold the ACP shell onto to the twig that the nymph was feeding on. This ensures that the husk of the host won’t fall off the twig prematurely exposing the parasitoid pupa to predators or inclement climatic conditions. Once the parasitoid has finished pupating, the adult wasp chews a perfectly circular hole near the head of the mummified ACP husk and the parasitoid emerges. After emergence it will mate and if it is a female, it will hunt for more ACP nymphs to attack. The presence of these emergence holes near the head of dried up ACP nymphs is very strong evidence that Tamarixia emerged from that host.

The second way Tamarixia can kill ACP nymphs is by host feeding. When Tamarixia host feeds, the female uses her ovipositor or egg laying tube at the posterior end of her abdomen to stab and mutilate the ACP nymph. This physical injury causes hemolymph (the equivalent of insect blood) to leak from the body and the parasitoid feeds on this fluid. Hemolymph is an important source of protein for female parasitoids, and the trauma of being stabbed then feed upon is sufficient to kill ACP nymphs. Only females can attack ACP nymphs in this manner because males lack an ovipositor because they don’t lay eggs.
Laboratory studies on the biology of Tamarixia suggest that through the combined actions of parasitism and host feeding, individual female parasitoids have the capacity to kill several hundred ACP nymphs during their life time.

Argentine ants tending an infestation of Asian citrus psyllid nymphs. Ants may hamper biological control of ACP by Tamarixia

Ants and ACP Biocontrol:At some release sites, ants, in particular the invasive Argentine ant, may have the potential to interfere with the biological control of ACP. Field observations strongly suggest that ants tend ACP nymphs and as a reward for guarding them, the ACP provide the ants honeydew, a sweet waste product that they excrete. We’ve also seen ants capture and eat Tamarixia parasitoids foraging in clumps or patches of ACP nymphs, and in some instances the ants have chased Tamarixia off the patch if they could not catch it. It is possible that when ACP infestations are heavily tended by ants, some sort of ant control may be needed if the natural enemies are to attack the pests. This problem is not unique to ACP, honeydew producing scales and mealybugs, for example, are also tended by ants, which in turn hampers effective biological control of these pests too.

Future Plans: Monitoring and release programs are ongoing, and UC Riverside is now ramping up the mass production of Tamarixia for expanded releases throughout ACP infested zones. It is hoped that as more Pakistani Tamarixia are released in southern California greater establishment rates will occur and natural spread will begin to fill in areas between release sites.

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Asian Citrus Psyllid

Mark Hoddle

Tamarixia Radiata

Tamarixia radiata and Natural Enemy Impacts on the Invasive Asian Citrus Psyllid in southern California

Anonymous — Wed, 18 Dec 2019 10:14:57 +0000

Tamarixia radiata and Natural Enemy Impacts on the Invasive Asian Citrus Psyllid in southern California Anonymous (not verified) Wed, 12/18/2019 - 02:14 More Blog Posts Erica Kistner October 31, 2014

Written by:
Erica J. Kistner (Postdoctoral Scholar, UC Riverside)

Photos by:
Mike Lewis, Mark Hoddle and Nayham Melhem

The Problem: Since its accidental introduction in 2008, the invasive Asian Citrus Psyllid (ACP) is now widespread throughout southern CA including San Diego, Imperial, Riverside, Los Angeles, Orange, and San Bernardino counties. ACP may present the greatest economic threat that California’s citrus industry has ever faced. This little insect is an efficient vector of a bacterium that causes a lethal citrus disease, huanglongbing (HLB), which is one of the most destructive diseases of citrus worldwide. There is currently no cure for this bacterial disease which kills susceptible commercial citrus varieties in as little as 5-8 years. California’s citrus industry is currently valued at $2 billion per year. Since 2005, Florida’s citrus industry has been hit hard by HLB. The spread of HLB in Florida by ACP has been estimated to have cost the Florida citrus industry $1.6 billion in losses over a 5 year period. In April 2012, the first case of HLB was detected in a residential site in Los Angeles County.

The remains of Tamarixia killed Asian citrus psyllid nymphs. The circular holes near the head indicate where the wasp emerged from its mummified host.

Ongoing Biocontrol Efforts: To reduce the spread of HLB into California’s commercial orange groves, a tiny parasitic wasp, Tamarixia radiata, sourced from Pakistan is currently being massed reared and released as a biocontrol agent throughout southern California. As of July 2014, approximately ~700,000 Tamarixia wasps have been released by the California Department of Food and Agriculture. This parasitoid has multiple stable populations and has even spread to sites where it was never released and it had likely established in southern California. Despite these massive rearing and distribution efforts, the efficacy of Tamarixia in controlling urban ACP population growth and spread remains unknown. Preliminary results of biweekly ACP surveys across 27 sites in Riverside and LA County suggest that Tamarixia may be limiting ACP densities.

Asian Citrus Psyllid, Diaphorina citri, life stages. UCNFA, G.O. Conville 1970.

ACP Life Cycle: ACP hatch from eggs and transition through 5 juvenile life stage known as nymphal instars before reaching adulthood (see photo above). ACP adults have wings and are excellent fliers. ACP generation time is short with development from egg to sexually mature adult taking ~2-4 weeks.

Natural Enemies and Allies: In addition to Tamarixia, ACP may have other enemies including naturally occurring predators. Generalist predators, including lady beetles are known to signficantly reduce ACP numbers in Florida, but their impact in California is unknown. To complicate matters further, the Argentine ant, another invasive pest, may be helping ACP thrive in southern CA. These ants have been observed to protect ACP colonies from their enemies (including Tamarixia). In exchange, colonies of ACP nymphs provide ants with honeydew, a sweet waste product that nymphs excrete (See photo above).

Argentine ants tending Asian citrus psyllid nymphs on our experimental colonies. These ants may interfere with biocontrol efforts by protecting ACP from Tamarixia and predators.

ACP Survival Experiments: To access the impact of natural enemies on ACP population growth, experimental ACP cohorts are currently being monitoring at three sites within Riverside County, CA where Tamarixia has been released and established. ACP cohorts of ~200 eggs are established in the lab on four citrus plants that are placed at field sites to assess the impact of natural enemies on these experimental ACP cohorts. Four treatments are evaluated to assess natural enemy impact on immature ACP: (1) potted plants are completely enclosed with a fine mesh bag to exclude all natural enemies, this treatment acts as a control to determine ACP survivorship rates in the absence of natural enemies (we expect survivorship rates to be high in this treatment is nothing is able to access the ACP and feed on it). (2) Potted plants are enclosed within a coarse mesh bag to prevent access by large predators while still allowing entry of small natural enemies like Tamarixia. This treatment provides information on how much mortality Tamarixia alone can inflict on ACP if these parasitoids can find ACP cohorts in the field. (3) A sticky barrier is applied to potted plant bases to prevent access to ACP by walking natural enemies (e.g., lacewing larvae). Only natural enemies that can fly (e.g., ladybugs and Tamarixia) will be able to land on plants to attack ACP eggs and nymphs, (4) Potted plants are fully exposed thereby allowing free access to ACP life stages by all natural enemies (i.e., walkers and flyers). Plants are examined every other day using a 10x lens and numbers of ACP by life stage are recorded per treatment. Predators observed on ACP patches or trapped in tangle foot barriers are identified. Parasitism by Tamarixia is easy to detect in the field since emerging adult wasps leave a circular exit hole in the body of the deceased ACP host (see photo above).

Experimental ACP cohorts at the UC-R Biocontrol Plot. Each potted citrus plant is home to families of ACP (known as cohorts) whose survival is monitored from egg to adulthood.

Results to Date: Preliminary results suggest that both predators and Tamarixia reduce experimental ACP numbers in California. Protection from natural enemies can increase ACP survival by 6-fold. Thus far, hover fly (Syrphidae) and green lacewing (Chrysopidae) larvae have been the most commonly observed predators, but spiders (Aranae) and lady beetles (Coccinellidae) have also been seen on experimental ACP colonies. Hover fly and green lacewing larvae have voracious appetites and may consume over 100 ACP nymphs before pupating (the non-feeding stage between insect larvae and adult life stages). ACP mortality from these hungry larvae can reach as high as 93% in some instances.

One experimental site with ACP cohorts in Riverside exhibited a 66.3% parasitism rate by Tamarixia when ACP cohorts were protected from walking predators and only a 1.4% parasitism rate when exposed to all enemies. Could this reduction in parasitism be the work of the Argentine ant? These ants have been observed tending experimental ACP colonies which likely protects them from natural enemies.

Green Lacewing (right) and hover fly larvae (left) found on experimental potted plants with ACP cohorts. Adults of both species lay their eggs next to psyllid and aphid colonies.

Future Plans: Argentine ants are abundant at all experimental sites and their interactions with ACP and natural enemies are being investigated. These experiments will continue over a year’s time (2014-2015) to compare seasonal variation in ACP densities through time.

Take Home Message: Our results suggest that predators as well as Tamarixia are helping limit ACP numbers at urban sites. In turn, your friendly neighborhood insects may help prevent the future spread of HLB in California by reducing ACP populations and this in turn helps to protect our commercial citrus production areas from ACP and HLB.

Argentine Ants, Asian Citrus Psyllid, Tamarixia radiata, UC Riverside

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First Official Release of Diaphorencyrtus aligarhensis in California for the Biological Control of Asian Citrus Psyllid

Anonymous — Wed, 18 Dec 2019 10:03:05 +0000

First Official Release of Diaphorencyrtus aligarhensis in California for the Biological Control of Asian Citrus Psyllid Anonymous (not verified) Wed, 12/18/2019 - 02:03 More Blog Posts Mark Hoddle December 19, 2014

The Problem

Figure 1. An adult male (left) and female (right) Diaphorencyrtus aligarhensis on a citrus leaf. Photo Mike Lewis, Center for Invasive Species Research, UC Riverside.

Asian citrus psyllid (ACP) is a serious threat to California’s citrus because it spreads a bacterium that causes a lethal disease of citrus, huanglongbing, which was first detected in Hacienda Heights, Los Angeles County in March 2012. One way to reduce the rate of spread of HLB is to reduce the populations of ACP living on citrus in urban areas. This will have two important impacts: (1) it will reduce the rate of spread of HLB by ACP, and (2) fewer ACP will migrate from urban areas into commercial citrus production areas threatening organic and conventionally-grown citrus. One way to suppress ACP populations in urban areas without the use of pesticides is through biological control, the use of natural enemies to reduce pest population densities.

On 16 December 2014, the biological control project targeting ACP took a significant step forward when 556 Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae) (Fig. 1) were released at the University of California Riverside (UCR) Biological Control Grove. The release occurred at 9:00am and was attended by approximately 40 people representing UCR, the Citrus Research Board (CRB), the California Department of Food and Agriculture (CDFA), local pest control advisors, and media representatives.

Figure 2. UC Riverside’s Chancellor Kim Wilcox (right) and Divisional Dean of Agricultural and Natural Sciences, Jodie Holt (left), releasing Diaphorencyrtus at the Biological Control Grove. Photo Mike Lewis, Center for Invasive Species Research.

The first of 15 vials that contained parasitoids was opened by Chancellor Kim Wilcox (Fig. 2), the remaining vials were distributed amongst attendees, who opened and tied them to branches of lemon trees in the Biocontrol Grove. The sex ratio of this Pakistani parasitoid is ~50% female and ~50% male. The road to releasing Diaphorencyrtus in California was long. The parasitoid was first collected from Punjab Pakistan in March 2011 and recovered from ACP nymphs until a sixth and final collecting trip was completed in April 2013. A total of 1,023 Diaphorencyrtus were collected in Pakistan and returned to the quarantine facility at UCR.

How Safe is Diaphorencyrtus for California?

Figure 3. Diaphorencyrtus sitting on the nose of Abraham Lincoln on a US penny. Photo Mike Lewis, Center for Invasive Species Research.

Diaphorencyrtus is a tiny parasitic wasp (Fig. 3), it can’t sting people or animals, it doesn’t eat plants, and unlike ACP it can’t spread the bacterium that causes huanglongbing, the disease that kills citrus. Safety testing to determine the host specificity of Diaphorencyrtus took almost 18 months to complete in quarantine at UCR. This process involved exposing this parasitoid to non-target psyllid species that included native psyllid species and psyllids used as weed biocontrol agents to determine its host range (i.e., the number of psyllid species it can attack) and host specificity (i.e., which psyllid species are most preferred for parasitism). Results from no-choice and choice tests were used to prepare an 84 page Environment Assessment Report that was submitted to USDA-APHIS for review on 1 November 2013. The results of experiments demonstrated that Diaphorencyrtus has a very strong preference for ACP nymphs and likely poses little environmental risk. On 24 November 2014, USDA-APHIS issued the official release permit, P526P-14-04034, to move Diaphorencyrtus out of quarantine for release and use in California as a biocontrol agent of ACP.

Overview of Diaphorencyrtus Biology

Figure 4. Diaphorencyrtus ovipositing in a third instar ACP nymph. Photo Mike Lewis, Center for Invasive Species Research, UC Riverside.

Diaphorencyrtus is an endoparasitoid that can parasitize second through fourth instar ACP nymphs, but second and third instars seem to be preferred (Fig. 4). All parasitized ACP nymphs, regardless of stage that is parasitized, continue to feed, develop, and molt to the fifth and final instar before they turn into mummies. Curiously, Diaphorenyrtus is unable to develop in late stage fourth instar (i.e., nymphs that are older than 7.5 days of age) as for some unknown reason parasitoid eggs don’t hatch (. Fifth instar ACP nymphs are also unsuitable for oviposition because the cuticle maybe too thick to pierce with the ovipositor and defensive twitching by these large nymphs may deter ovipositing females.

Figure 5. Asian citrus psyllid mummies showing the position of exit holes chewed by adult Diaphorencyrtus (left, hole is in posterior of the ACP mummy) and Tamarixia (right, hole is in anterior of the ACP mummy). Photo Mike Lewis, Center for Invasive Species Research, UC Riverside.

Development from egg to adult parasitoid emergence takes about 16 days at 77^oF (25^oC). During this developmental period parasitoid larvae passes through four larval instars, or developmental stages, before reaching a pre-pupal stage that transitions into the pupa. Developmental times for Diaphorencyrtus eggs, first and second instar larvae are about 2 days; the third, fourth, and pre-pupal stages last around 1 day, while the pupal stage takes seven days to complete. During the third instar, Diaphorencyrtus larvae use secretions from the tip of the abdomen to anchor themselves within the thoracic region of body cavity of the ACP nymph. Once secured, parasitoid larvae then position themselves with the posterior of their bodies aligned with the head of the ACP nymph and the larval head or anterior region facing the posterior of the host.

Figure 6. An adult female Diaphorencyrtus feeding on Asian citrus psyllid nymph honeydew. Photo Mike Lewis, Center for Invasive Species Research, UC Riverside.

Therefore, when adult Diaphorencyrtus emerge, they chew an exit hole at the posterior end of the ACP mummy through which they escape. In contrast, Tamarixia chews an exit hole in the anterior or head region of the ACP nymph to emerge (Fig. 5). Diaphorencyrtus females obtain protein for maturing eggs by host feeding on ACP nymphs. To host feed, females use their ovipositor to pierce the body of the ACP nymph, hemolymph or insect blood, leaks from these wounds and is eaten by females. The trauma of being stabbed and then fed upon is often sufficient to kill ACP nymphs. Additionally, adult Diaphorencyrtus may gain nutrition from eating ACP honeydew, the dried white material that is exuded by feeding nymphs (Fig. 6).

The Diaphorencyrtus Release Plan for California

Releases of Diaphorencyrtus are planned for areas where Tamarixia has either not been released or surveys indicate that selected areas near Tamarixia release sites have little or no activity associated with this parasitoid. The reason for this strategy is to minimize competition between Diaphorencyrtus and Tamarixia so as to give Diaphorencyrtus the best possible chance to establish. To select sites for Diaphorencyrtus releases we are working closely with the CDFA to identify suitable sites that encompass a variety of different climatic conditions. For example, Tamarixia-free sites in the Coachella Valley have been identified and scouting is underway to look for suitable release areas in Riverside and Los Angeles Counties. Past experience suggests that establishing more than one natural enemy of a citrus pest in California can increase the chances of successful biological control. Perhaps one of the best recognized cases is that concerning the cottony cushion scale, Icerya purchasi, with the predatory beetle, Rodolia cardinalis, and the parasitic fly, Cryptochaetum iceryae. Surveys indicate that the beetle provides control in arid desert interior regions, while the fly dominates in cooler coastal areas where citrus is grown. Parasitoid releases will be made when ACP stages are abundant for parasitism and host feeding. Site security needs to be ensured to minimize preventable accidents such as pesticide sprays or pruning of trees which could accidentally eradicate incipient Diaphorencyrtus populations.

How Well Will Diaphorencyrtus Control ACP in California?

Diaphorencyrtus populations sourced from Taiwan, Vietnam, and China (these are all female colonies) have failed to establish in Florida despite multiple release efforts involving more than 11,000 parasitoids. Reasons for this are unknown, but could be due to heavy pesticide use to control ACP, lack of synchrony between releases and ACP life stages suitable for parasitism, competition from Tamarixia, and possible predation of parasitized nymphs. Other factors may include low genetic diversity (because these parasitoids in Florida are all female they don’t reproduce sexually) and too little investment put into release and establishment efforts.

In many countries Tamarixia and Diaphorencyrtus coexist (e.g., Vietnam, China, and Taiwan) and in Pakistan the results of ~ 2.5 year long surveys in kinnow mandarin and sweet orange suggest that average year round parasitism of ACP nymphs by Diaphorencyrtus is ~ 20% while Tamarixia accounts for ~30% parasitism each year (Khan et al., 2014). In Saudi Arabia, Diaphorencyrtus may be the only parasitoid species attacking ACP nymphs infesting Mexican limes with maximum parasitism rates of 64-71% being recorded.

It is impossible to predict what level of ACP suppression Diaphorencyrtus is likely to provide in California. It is anticipated that if Diaphorencyrtus establishes it will complement the activity of Tamarixia thereby increasing overall ACP mortality. It is possible that if Diaphorencyrtus does establish in may have ecoclimatic preferences different to that of Tamarixia which may allow it to provide control in areas where Tamarixia is not effective. The only way to determine these potential outcomes is through a multi-year research program that tracks the establishment, spread, and impact of Diaphorencyrtus on ACP in urban and commercial citrus production areas in California.

Asian Citrus Psyllid, Mark Hoddle, News, UC Riverside

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Psyllaphycus diaphorinae: Another Natural Enemy from Pakistan for ACP Biocontrol?

Anonymous — Wed, 18 Dec 2019 09:31:51 +0000

Psyllaphycus diaphorinae: Another Natural Enemy from Pakistan for ACP Biocontrol? Anonymous (not verified) Wed, 12/18/2019 - 01:31 More Blog Posts Allison Bistline-East January 11, 2016

Written by: Allison Bistline-East
Email: a.bistline-east1@nuigalway.ie
More Research: UCR Biocontrol Website

The Problem. In 2008, the Asian citrus psyllid (ACP), Diaphorina citri (Hemiptera: Liviidae), was first detected in California. Since its establishment in California, commercial citrus growers and homeowners alike have become familiar with this notorious pest and the threat it represents as a vector of the bacterium, Candidatus Liberibacter asiaticus, which causes the lethal citrus disease huanglongbing (HLB). As of July 2015, there have been two confirmed cases of HLB-positive citrus trees in California, both on residential properties in Los Angeles County.

Female Psyllaphycus diaphorinae emerging from a Diaphorencyrtus aligarhensis-ACP mummy.

Natural Enemies for ACP Biocontrol. Because ACP-HLB poses such a significant threat to the California citrus industry, which generates over $3 billion annually and provides over 26,000 jobs, ACP population control has been a primary focus of both UCR entomologists and the California Department of Food and Agriculture (CDFA). A classical biological control program to reduce ACP populations in urban areas began with the release of Tamarixia radiata in December 2011, and in December 2014, a second parasitoid, Diaphorencyrtus aligarhensis, was added to the release program with the intent of establishing a complementary set of parasitoids that attack ACP nymphs. There has been some question as to how many different natural enemy species are optimal in biological control programs, and in several instances a complex of several species have been shown to be most effective, especially when the target pest infests different environments (Denoth 2002). In its home range, the Indian subcontinent and Asia, a guild of up to nine different parasitoid species were described attacking ACP nymphs by Mohammad Hussain and Dina Nath (1927). However, the identity of just one species, Tamarixia radiata, was determined. This led researchers in the Hoddle lab (UCR) on an investigation to determine the identities of the other parasitoid species putatively attacking ACP nymphs in Punjab Pakistan, with the intent of discovering additional natural enemies to use in the ACP control program in California.

It is likely one of the unnamed species recovered in Hussain and Nath’s (1927) study was Psyllaphycus diaphorinae. Nearly 50 years after the initial study, Mohammed Hayat (1972) formally described P. diaphorinae from specimens recovered in Punjab, India, a region immediately adjacent to Punjab, Pakistan where T. radiata and D. aligarhensis were collected and subsequently released in California for ACP biocontrol. In April 2013, six live female P. diaphorinae were returned to the Insectary and Quarantine Facility at UCR from a natural enemy collecting trip in Punjab, Pakistan. This collection was the first to return live P. diaphorinae, and the recovered females were immediately exposed to ACP nymphs at every juvenile stage to determine the preferred host stage of this potential parasitoid of ACP nymphs.

P. diaphorinae Host Determination. To the surprise of UCR researchers, the preferred host of P. diaphorinae was not ACP at all. After exposing the P. diaphorinae females to 90 ACP nymphs no successful parasitism was observed. The females were then subjected to further exposure trials, this time sequentially to T. radiata larvae developing inside ACP (“mummies”), D. aligarhensis mummies, and additional unparastitized ACP nymphs. Contrary to the description given by Hayat, which was based solely on the morphology of preserved specimens, the results of these exposure trials determined that P. diaphorinae actually parasitizes developing T. radiata or D. aligarhensis within an ACP nymph, and not the ACP nymph itself! This type of parasitism, where one parasitoid targets another within a host, is known as hyperparasitism, and these types of parasitoids are known as hyperparasitoids. Basically, they’re parasitoids of parasitoids!

Female (top) and male (bottom) Psyllaphycus diaphorinae adults.

Investigating the Biology of P. diaphorinae. Once the hosts of P. diaphorinae were identified, an evaluation of many important biological traits, such as host preference, developmental rate, and adult longevity, were possible. Results from these experiments indicated that D. aligarhensis was a more suitable host than T. radiata, based on P. diaphorinae producing both more offspring overall and a higher ratio of female-to-male offspring on D. aligarhensis. P. diaphorinae offspring also developed slightly faster on D. aligarhensis (about 16.5 days on average, at 27°C) versus T. radiata (about 17 days average). Because D. aligarhensis was shown to be the better host, adult longevity was measured only for P. diaphorinae emerging from D. aligarhensis mummies. Male and female P. diaphorinae adults had an average lifespan of 17 days and 20 days, respectively, when held individually, and 20 days and 30 days, respectively, when held as male-female pairs. These experiments provided a valuable first glimpse into the biology of P. diaphorinae. Experiments also investigated the effects of various temperatures on developmental rate and adult longevity, which will allow researchers to determine the optimal conditions for this hyperparasitoid. For a more in-depth look at these experiments, see Bistline-East and Hoddle 2015.

Ecological interactions in the ACP-parasitoid complex. Hyperparasitoids exert negative effects on primary parasitoid populations, resulting in indirect positive effects on ACP

Why Hyperparasitoids Matter. The existence of hyperparasitoids may greatly impact biological control programs. Because hyperparasitoids target the natural enemies that are being used to control a specific pest species, this causes a mediating effect on parasitoid impact, and an overall indirect positive outcome for the pest species. The good news is that there are no known species of hyperparasitoids in California that are found targeting T. radiata or D. aligarhensis in their native range, including P. diaphorinae. The bad news is that there are eight known genera that contain hyperparasitoids in both California and ACP’s native range, so there is still the possibility that over time one or more species within these genera that are native to California could eventually shift hosts and attack introduced ACP natural enemies. As far as we are aware, California is an “enemy-free zone” for T. radiata and D. aligarhensis, which is expected to allow incipient natural enemy populations to establish, spread, and potentially suppress ACP populations effectively.

References

Bistline-East, A. and M.S. Hoddle. 2015. Biology of Psyllaphycus diaphorinae (Hymenoptera: Encyrtidae), a Hyperparasitoid of Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae) and Tamarixia radiata (Hymenoptera: Eulophidae). Annals of the Entomological Society of America in press
Denoth, M., L. Frid, and J. H. Myers. 2002. Multiple agents in biological control: improving the odds? Biol. Cont. 24: 20-30.
Hayat, M. 1972. Descriptions of two new genera and species of Encyrtidae (Hymenoptera, Chalcidoidea), with notes on some described species. Acta ent. bohemoslov. 69: 207-214.
Hussain, M. A. and D. Nath. 1927. The citrus psylla (Diaphorina citri) (Psyllidae: Homoptera). Mem. Dept. Agric. India, Entomol. Ser. 10: 5-27.

Asian Citrus Psyllid, Psyllids

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Asian Citrus Psyllid

Psyllids