In a ground-breaking discovery encompassing six years of research, an international team of scientists led by UC Davis chemical ecologist Walter Leal announced they've identified the sex pheromone of the pest, which feeds on citrus and transmits the bacteria that causes the deadly citrus greening disease known as Huanglongbing (HLB).
Leal, a native of Brazil and a fellow of both the Entomological Society of America and the Entomological Society of Brazil, revealed the discovery during his presentation Dec. 5 at the 10th Annual Brazilian Meeting of Chemical Ecology in Sao Paulo. His team included scientists from UC Davis, University of Sao Paulo, and the Fund for Citrus Protection (FUNDECITRUS) from the state of Sao Paulo.
“Dr. Leal's discovery of the Asian citrus psyllid pheromone is a significant breakthrough in preventing the spread of this serious citrus insect, and may offer a less toxic method for its control,” said integrated pest management specialist Frank Zalom, distinguished professor with the UC Davis Department of Entomology and Nematology and a past president of the Entomological Society of America. He was not involved in the study.
“Having a lure to dramatically improve captures of this psyllid with the conventional sticky traps is a major progress toward integrated pest management,” said Professor Jose Robert Parra of the University of Sao Paulo.
Identifying the sex pheromone proved “complicated and quite a challenge” because of the insect's complex behavior and biology, said Leal, a UC Davis distinguished professor who has discovered the sex pheromones of moths, beetles, bugs, cockroaches, mites and other arthropods. A patent was filed Friday, Dec. 1, and journal publication is pending.
Citrus trees infected with HLB usually die within five years, according to the UC Statewide Integrated Pest Management Program. There is no known cure. “The only way to protect trees is to prevent spread of the HLB pathogen in the first place, by controlling psyllid populations and removing and destroying any infected trees,” UC IPM says on its website.
Native to Asia, the Asian citrus psyllid, Diaphorina ciri, was first detected in the United States in June 1998 in Palm Beach County, Florida, and in California in August 2008 in San Diego County. Scientists discovered HLB in Florida in August 2005, and in Los Angeles in March 2012. The mottled brown insect, about 3 to 4 millimeters long, or about the size of an aphid, is now widespread throughout Southern California and is now found in 26 of the state's 58 counties.
The Asian citrus psyllid, or ACP, feeds on new leaf growth of oranges, lemons, mandarins, grapefruit and other citrus, as well as some related plants. Infected psyllids can transmit the bacterium Candidatus Liberibacter asiaticus, which causes the fatal citrus disease. An early symptom of HLB in citrus is the yellowing of leaves on an individual limb or in a sector of a tree's canopy.
Currently growers are using yellow sticky traps to detect the insect and to monitor the population. “Efficient lures,” Leal said, “are sorely needed for sticky traps, particularly for early ACP detection. Otherwise, growers have to resort to regular sprays to avoid infection given that infected insects from gardens and noncommercial areas migrate to citrus farms.”
Pheromones and other semiochemicals are widely used in agriculture and medical entomology. “Growers use them as lures in trapping systems for monitoring and surveillance, as well as for strategies for controlling populations, such as mating disruption and attraction-and-kill systems,” Leal noted.
Although ACP is present in Arizona and California, the disease itself has not been established, Leal said. “The emphasis is on detection, eradication and limiting the spread of the disease. In Florida, where HLB is widespread, monitoring ACP populations is essential to avoid reinfection after eradication of infected plants.”
The detection of the pest has led to widespread eradication of citrus trees in China, Brazil and the United States. “In Brazil as many as 46.2 million citrus trees, representing 26 percent of the currently planted trees, have been eradicated since the detection of HLB in 2004,” Leal said. “In Florida, HLB has caused severe losses to the citrus industry. This year's production loss is estimated to be about 28 million fewer boxes of oranges than in 2014-2015.”
The announcement of the discovery coincides with the 40th anniversary celebration of FUNDECITRUS in Araraquara, Sao Paolo. “I am delighted that Walter Leal accepted our challenge to work on this project as the lead investigator,” said Juliano Ayres, FUNDECITRUS director. “The combination of his work ethics and qualifications are unparalleled. And, he loves challenges.”
In response to the ACP invasion in California, the California Department of Food and Agriculture (CDFA) has launched an extensive monitoring program to track the distribution of the insect and disease. They check yellow sticky traps in both residential areas and commercial citrus groves, and also test psyllids and leaf samples for the presence of the pathogen.
Survey methods for ACP include visual inspections, sweep netting, and placement of yellow sticky traps in trees in citrus nurseries, commercial citrus-producing areas and residential properties throughout the state, according to the CDFA. They also place sticky traps in California fruit packing houses, specialty markets, retail stores and airports that receive such produce from areas known to be infested with ACP.
Since August 2008, ACP has now been detected in 26 of California's 58 counties: Alameda, Contra Costa, Fresno, Imperial, Kern, Kings, Los Angeles, Madera, Merced, Monterey, Orange, Placer, Riverside, San Benito, San Bernardino, San Diego, San Joaquin, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Solano, Stanislaus, Tulare, Ventura, and Yolo. “The ACP has the potential to establish itself throughout California wherever citrus is grown,” the CDFA says on its website.
CDFA has set up a hotline at 1-800-491-1899 for residents to report suspicious insects or disease symptoms in their citrus trees.
California Department of Food and Agriculture (CDFA)
Save Our Citrus: Hotline Information
UC Agriculture and Natural Resources (UC ANR)
If you attended the 2017 Entomological Society of America (ESA) meeting, held recently in Denver, you probably recognized a familiar face and his research.
This is the third year he has won first-place honors in the President's Prize competition, an opportunity for graduate students to present their research.
Boudinot, who studies classification and evolution of morphology, delivered a 10-minute oral presentation in the Systematics, Evolution and Biodiversity Section on "The Protopodal Theory of Genitalic Evolution in the Hexapoda (Arthropoda: Mandibulata: Pancrustacea)."
Judges evaluate the oral presentations on scientific content (50 percent) and presentation (50 percent). For scientific content, judges score them on introduction and background with pertinent literature cited; objectives clearly stated and concise; materials and methods (study design) clear and concise; results and discussion clear, concise and accurate; and significance of results to field of study. Judges evaluation the presentation on organization, slides and delivery.
For his work, he received a one-year free membership in ESA, a $75 cash prize, and a certificate.
Boudinot's previous President's Prizes were for presentations on the male genitalia of ants, and for providing the first male-based identification material for the ant genera of the New World.
"I study ants because they are a unique evolutionary radiation of wingless, social wasps; through the study of their genetic and morphological diversity, we are better able to understand the ecological and biogeographic components of the process of speciation," Boudinot said today. "I came to study ants through several years of work I did as an undergraduate sorting and identifying ants from thousands of leaf litter samples collected in Central America by the Leaf Litter Arthropods of MesoAmerica project, which I was involved in (see photo of him in Honduras during 2010, as well as a little blurb from the year before he joined UC Davis graduate program)."
Boudinot traces his initial interest in the taxonomic and morphological diversity of ants through direct observational experience. Now, as a member of the Ward Lab, he continues his work, which encompasses three components:
- the diversity and classification of male ants in the New World
- a reclassification of the Formicidae based on phylogenetic analyses combining fossils with living taxa, and
- a study of the morphological evolution of the abdomen of insects, borne out of work done in projects (1) and (2).
Boudinot completed his undergraduate work at the Evergreen State College, Olympia, Wash., and spent a year working as a research technician at the University of Utah before starting his graduate work in 2014 with advisor Phil Ward. He focuses his research on evolution and ecology, approached from the perspective of systematics. “I integrate several lines of inquiry to answer historical evolutionary questions, including morphological and molecular phylogenetics, paleontology, and traditional comparative morphology,” Boudinot related. “I specialize on the skeletomusculature system of the male genitalia of the Hexapoda and the classification of the Formicoidea.”
Ants are highly diverse, with more than 13,000 known species, Boudinot says. "They are, however, but one stitch in the diversity of all insects, and we are entering a new era for the study of morphology in the 21st century."
The genitalia of male insects are fascinating, he said. "Both male and female insect genitalia are derived from the appendages of a pair of abdominal segments. Evidence from the skeletomusculature indicates that these structures are really legs of a crustacean ancestor that have been modified for numerous reproductive tasks--from copulation and insemination, to singing and silk-spinning."
When he's not studying ants, you can find Brendon Boudinot serving as president of the Entomology Graduate Student Association (EGSA), his second term at the helm. In this capacity, he functions as student liaison to the faculty, and as chair or co-chair of several committees, both for departmental and graduate student events (including the Entomology Seminar Series, Retreat Committee, annual Graduate Student Recruitment Day, Picnic Day, and various graduate student social events).
UC Davis doctoral candidate Sarah Silverman of the James R. Carey lab joined Boudinot in the winners' circle at the ESA meeting. She won a second place award in the President's Prize competition, delivering a 10-minute oral presentation in the Diptera-Mosquitoes category of the Medical, Urban, and Veterinary Entomology Section, on “Population as Cohort: Interpreting the Mortality Patterns of Wild-Caught Adult Mosquitoes of Unknown Ages.”
Her work at UC Davis is in the field of insect demography. “I specifically study insect lifespan in the wild," she said, "as well as the the age-structure of insect populations in the wild using an innovative methodological approach: the capture of live-insects in the wild which are then maintained and observed in the lab until death." Silverman completed her bachelor's degree in environmental science at McGill University in Montreal. For her undergraduate thesis, she studied the phenology of wild Osmia bees./span>
Hamby, an assistant professor and extension specialist in the Department of Entomology at the University of Maryland-College Park, will receive the Early Career Professional (ECP) Extension Award during the annual meeting of the Entomological Society of America (ESA), Nov. 5-8 in Denver, Colo. The awards breakfast is set Nov. 7 in the Four Seasons Ballroom, Big Blue Bear, Colorado Convention Center.
The award is given to an early professional who excels in entomological Extension.
The ESA spotlighted her in its program: "Her research and extension program addresses invasive and emerging insect pest issues, evaluating and optimizing pest management programs, and development of sustainable alternative management tactics. Dr. Hamby is particularly interested in understanding and exploiting insect interactions with free-living microorganisms for sustainable pest management."
"Her current work includes characterizing spotted wing drosophila's interactions with yeast and fruit rot microorganisms and developing cultural control tactics for this invasive pest of small fruit. Her lab is also evaluating the pest suppression benefits and non-target impacts of neonicotinoid seed treatments in mid-Atlantic grain crop rotations."
"Dr. Hamby delivers timely, research-based extension programming via extension publications, field days, and winter meetings, serving the needs of Maryland's grain producers and diversified small fruit farmers. In addition to her research and extension responsibilities, Dr. Hamby teaches integrated pest management and provides K-12 outreach with hands-on pest management activities."
Hamby received all three of her degrees from the University of California, Davis. While studying for her bachelor's degree in environmental toxicology, specializing in ecotoxicology, she completed the integrated studies honors program and graduated with highest honors in June 2009, making the dean's honors list. She went on to obtain her master's degree (March 2012) and doctorate in entomology (March 2014), studying with major professor and integrated pest management specialist Frank Zalom, distinguished professor, UC Davis Department of Entomology and Nematology, and a past president of the ESA. Her doctoral dissertation, completed in 2014, covered: “Biology and Pesticide Resistance Management of Drosophila suzukii in Coastal California Berries."
At UC Davis, Hamby was supported by a National Science Foundation Research Scholarship and went on to win the coveted John Henry Comstock Award from the Pacific Branch, ESA. She compiled a near perfect 4.0 grade point average during her years at UC Davis.
Hamby joined the ESA in 2009 and has presented her research at many of the annual meetings.
The ESA, founded in 1889, is the world's largest organization serving the professional and scientific needs of entomologists and people in related disciplines. Its nearly 7,000 members are affiliated with educational institutions, health agencies, private industry, and government. Members are researchers, teachers, extension service personnel, administrators, marketing representatives, research technicians, consultants, students, and hobbyists.
If you're addicted to insects or insect photography, you'll want to see the international award-winning images on the Insect Salon website. Each year the Peoria (Ill.) Camera Club hosts the contest in conjunction with the Entomological Society of America (ESA).
The subjects are primarily insects but can also include spiders and related arthropods, such as barnacles, crabs, lobsters, shrimp, centipedes and millipedes. For your work to be accepted in the Insect Salon showcase, it must score at least 12 points. Those who score 15 are selected medalists.
The ESA, a professional insect-science organization of some 7000 members, showcases these images at its annual conferences. This year's conference, set Nov. 5-8 in Denver, Colo., is appropriately themed "Ignite. Inspire. Innovate."
The winning photographers this year represent 16 countries: Argentina, Australia, Belgium, Brazil, Canada, Finland, France, Germany, Italy, Malayasia, Slovenia, South Africa, Taiwan, United Arab Emirates, United Kingdom and the United States. Some images are from ESA members, and some are from alumni of the BugShot Macro Photography Workshops.
Malaysia-based photographers anchored the winners' circle:
- The best-of-show medal went to Tommy Teh of Malaysia for "Hunger For Food 3"
- The medal for most unusual: Andrews Ruggen of Argentina for "Convivencia"
- The medal for best storytelling: Alek Low of Malaysia for "Craving For Food"
- The medal for best image from a non-ESA member: Kawawa Wong Yik Siang of Malaysia for "Hungry Jumping Spider"
- The medal for best image from an ESA member: Wei Fu of Ontario, Canada for "Bite Tightly"
- The medal for best image from a Peoria Club Camera member: John Weidman of Peoria, Ill. for "Argiope Securing Grasshopper"
You can view them all by accessing the Insect Salon website and then clicking on the image titles. The site includes the name of the photographer, city/country of residence, and the title of the image.
Due to copyright concerns, I'm not posting the winning images, but posting two of mine that were accepted for the 2017 Insect Salon showcase:
- "Faster than a Speeding Bullet" shows a long-horned bee (Melissodes agilis) in flight, speeding over a Mexican sunflower (Tithonia rotundifolia). This image received one of the 19 honorable mentions. (Image taken with a Nikon D500 camera with a 70-180mm lens. Settings: ISO 2500, f-stop 16, and shutter speed of 1/1000 of a second)
- "Under Attack!" shows a long-horned bee (Melissodes agilis) targeting a Red Admiral butterfly (Vanessa atalanta), also on Tithonia. (Image taken with a Nikon D500 with a 70-180mm lens. Settings: ISO 2000, f-stop 7, and shutter speed of 1/3200 of a second.)
These might inspire you to enter the 2018 Insect Salon competition.
It's a Macro World out there!
Bees and blister beetles, yes.
We remember writing about her work in April of 2013 when she addressed the Nor Cal Entomology Society (now folded) about her research on how blister beetle nest parasites cooperate to mimic the sex pheromone of a digger bee. She had just returned from the Mojave National Preserve, tracking the solitary bee Habropoda pallida and its nest parasite, a blister beetle, Meloe franciscanus.
Fascinating research! Saul-Gershenz, who grew up in New York, studies the chemical ecology and parasite-host interactions of solitary native bees and their nest parasites across the western U. S., including the coastal sand dunes of Oregon and the Mojave Desert in south-central California.
"The solitary bee is the first native bee to emerge in the spring on the Kelso Dunes in the Mojave National Preserve," she told us. “The adult beetles emerge on the dunes in the winter months at Kelso Dunes and feed exclusively on the leaves of Astragalus lentiginosus which leafs out in January."
The bee's emergence is generally synchronized with the onset of blooms of the Borrego milkvetch, which is the sole host plant of adults of the blister beetle at Kelso Dunes.
Basically, the larvae of the parasitic blister beetle produce a chemical signal or allomone, similar to that of a female bee's pheromone to lure males to the larval aggregation. The larvae attach to the male bee on contact and then transfer to the female during mating. The end result: the larvae wind up in the nest of a female bee, where they eat the nest provisions and likely the host egg.
Leslie is now Dr. Saul-Gershenz. She received her doctorate in entomology in May 2017. And on Wednesday, Oct. 18, she will share her research at her exit seminar, "Host Range Evolution of the Bee Parasite Meloe franciscanus," set from 4:10 to 5 p.m. in 122 Briggs Hall, Kleiber Hall Drive.
"We report that different populations of M. franciscanus exhibit local adaptations that mimic both the behaviors and the chemical composition of the sex pheromones of locally available bee host species," she writes in her abstract. "We compared a population of M. franciscanus larvae, known as triungulins, parasitizing nests of Habropoda miserabilis (Hymenoptera: Apidae) from the coastal sand dunes of Oregon with a population parasitizing the congener H. pallida in the Mojave Desert in south-central California. We determined that M. franciscanus populations are the same species using molecular analyses.
Working in collaboration with the Neal Williams bee lab and the Steve Nadler molecular lab in the UC Davis Department of Entomology and Nematology, she and chemical ecologist Jocelyn Millar at UC Riverside found that multiple populations of the blister beetle Meloe franciscanus are locally adapted to different bee hosts in different allopatric populations. (Professor Williams is a pollination ecologist, and Nadler is a nematologist and chair of the department.)
The UC Davis evolutionary ecologist also explored which functional traits of hosts are useful for predicting parasite host range. In another study, she brought together a dream team of bee biologists and received funding from the Bureau of Land Management to study the impact of utility-scale solar development on desert bees. This study documented that these landscapes are biologically rich, even in drought years, and contain a minimum of 114 species of bees including six undescribed species of bee.
The significance of her work?
"Our research has added to the understanding of the communication signals of bees in the genus Habropoda," she related. "We now know that they use long-chain hydrocarbons for the female sex attractant and vary the position of the double bounds in different components and vary proportions of these components to avoid cross attraction among closely related species. Parasites co-opt this communication channel to deceive male bees in the Meloe-Habropoda system.
"In our host functional trait research we show that annual host abundance and host abundance from year to year, as well as local temporal overlap are highly predictive of host range."
Results on the impact of utility-scale solar development on desert bees showed high bee species diversity in the Mojave and western Sonoran region. "This suggests the importance of careful regional planning and additional research to protect this area of significant floral and fauna biodiversity," she said.
Future plans? To continue her research.
Leslie Saul-Gershenz, recipient of numerous grants and author of a number of publications ranging from peer-reviewed papers to books, is the co-founder of the Bay Area-based SaveNature.Org and director of Research and Conservation (1988 to present). The international conservation consortium works with partners to protect ecosystems around the world.
She is also a 2004 graduate of The Bee Course, an intensive 10-day workshop sponsored by the American Museum of Natural History at the Southwestern Research Station, Portal, Ariz. One of the instructors is Robbin Thorp, distinguished emeritus professor of entomology at UC Davis, also one of her many collaborators.
Among her other current collaborators: scientists Lynn Kimsey, Neal Williams, Tom Zavortink, Rebecca Hernandez, all of UC Davis; Terry Griswold, USDA-ARS, Bee Biology Lab; Monica Geber, Cornell University; and John Ascher, National University of Singapore.
Her next presentations of her research will be at the Entomological Society of America's annual conference, "Ignite, Inspire, Innovate," scheduled Nov. 5-8 in Denver,Colo., and the California Native Plant Society Conservation Conference, scheduled Feb. 1-3, 2018 in Los Angeles.