The insect, a native of Asia, was first detected in the United States (Palm Beach County, Florida) in 1998, and California (San Diego County) in 2008. HLB, the bacterial disease that it transmits, was first detected in Florida in 2005, and in California (Hacienda Heights, Los Angeles County), 2012.
“The ACP has the potential to establish itself throughout California wherever citrus is grown,” according to the California Department of Food and Agriculture (CDFA).
Now an international team of scientists, led by chemical ecologist Walter Leal of the University of California, Davis, has discovered a new lure or male attractant that's more efficient and effective than the current trap surveillance system of yellow sticky traps.
“Our newly discovered lure captures an average of three times more ACP than the current trapping system, the sticky yellow traps,” said Leal, a distinguished professor in the Department of Molecular and Cell Biology and a former chair of the Department of Entomology and Nematology. “And it works in areas with low population densities. This is particularly important in California, because HLB is already established in urban areas and, therefore, trap surveillance systems are at a premium.”
The research, “Laboratory and Field Evaluation of Acetic Acid-Based Lures for Male Asian Citrus Psyllid, Diaphorina citri, is published today (Sept. 9) in Scientific Reports. It can be accessed free online at https://www.nature.com/articles/s41598-019-49469-3.
The 16-member team, which includes scientists from Brazil and Costa Rica and Benjamin Lehan of California State Polytechnic University, Pomona, wrote in their abstract: “Lures are much needed for improving ACP trapping systems for monitoring populations and surveillance. Previously, we have identified acetic acid as a putative sex pheromone and measured formic acid- and propionic acid-elicited robust electroantennographic responses. We have now thoroughly examined in indoor behavioral assays (4-way olfactometer) and field tests the feasibility of these three semiochemicals as potential lures for trapping ACP. Formic acid, acetic acid, and propionic acid at appropriate doses are male-specific attractants and suitable lures for ACP traps, but they do not act synergistically.”
“An acetic acid-based homemade lure, prepared by impregnating the attractant in a polymer, was active for a day,” they wrote. “A newly developed slow-release formulation had equal performance but lasted longer, thus leading to an important improvement in ACP trap capture at low population densities.”
“The disease has ravaged the citrus industry in China and Brazil,” said Leal, a native of Brazil. “In Brazil, about one-fourth of the citrus trees in the state of São Paulo has been eradicated since 2004 as part of an HLB control strategy. Florida has also sustained severe losses.
Now the disease threatens California's citrus growers “Of note, 1,100 findings of HLB in urban, but not in commercial orchards, suggest that the disease is already established in urban areas in California,” the scientists wrote. “Monitoring ACP populations is essential for integrated vector management and, more importantly, for surveillance. One of the challenges for abatement personnel in areas of low ACP densities is to capture the vector to determine infection status so that control strategies can be implemented before HLB is spread. Therefore, the development of trapping systems is at a premium, particularly the discovery of lures for enhancing ACP captures in areas of low populations.”
Earlier, an international team of scientists led by Leal identified the sex pheromone of the Asian citrus psyllid. Leal, a fellow of the Entomological Society of America and the Entomological Society of Brazil, announced the discovery, encompassing six years of research, at the 10th Annual Brazilian Meeting of Chemical Ecology in Sao Paulo in December 2017. (See Bug Squad blog)
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.
In response to the ACP invasion in California, the 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.
CDFA has set up a hotline at (1-800-491-1899) for residents to report suspicious insects or disease symptoms in their citrus trees.
They manage to find us, don't they? Even when we're doing our best to try to avoid them!
It's not so well-known that mosquitoes, both male and female, frequent plants to feed on nectar for energy.
And now UC Davis chemical ecologist Walter Leal and scientists Fangfang Zen and Pingxi Xu of the Leal lab have discovered that the odorant receptors from the southern house mosquito, Culex quinquefasciatus, and the yellow fever mosquito Aedes aegypti, are sensitive to floral compounds.
The manuscript: "Odorant Receptors from Culex quinquefasciatus and Aedes aegypti Sensitive to Floral Compounds."
The team, led by Leal, a distinguished professor in the Department of Molecular and Cellular Biology and a former chair of the UC Davis Department of Entomology, cloned the genes of several odorant receptors from the mosquitoes and tested them, using egg cells of Xenopus toads. They exposed the cloned receptors to different scent chemicals.
"We are delighted to find out how mosquitoes smell plant-derived compounds and are repelled by them," Leal said. "These findings may lead to the discovery of better repellents from natural sources."
"Mosquitoes rely heavily on the olfactory system to find a host for a bloodmeal, plants for a source of energy and suitable sites for oviposition," the scientists explained in their abstract. "Here, we examined a cluster of 8 odorant receptors (ORs), which includes one OR, CquiOR1, previously identified to be sensitive to plant-derived compounds. We cloned 5 ORs from Culex quinquefasciatus and 2 ORs from Aedes aegypti, ie, CquiOR2, CquiOR4, CquiOR5, CquiOR84, CquiOR85, AaegOR14, and AaegOR15 and then deorphanized these receptors using the Xenopus oocyte recording system and a large panel of odorants. 2-Phenylethanol, phenethyl formate, and phenethyl propionate were the best ligands for CquiOR4 somewhat resembling the profile of AaegOR15, which gave the strongest responses to phenethyl propionate, phenethyl formate, and acetophenone. In contrast, the best ligands for CquiOR5 were linalool, PMD, and linalool oxide. CquiOR4 was predominantly expressed in antennae of nonblood fed female mosquitoes, with transcript levels significantly reduced after a blood meal. 2-Phenylethanol showed repellency activity comparable to that of DEET at 1%. RNAi experiments suggest that at least in part 2-phenylethanol-elicited repellency is mediated by CquiOR4 activation."
Meanwhile, Leal is gearing up for the 2019 Entomological Society of America (ESA) meeting in St. Louis, Mo., where he will deliver the Founders' Memorial Award Lecture on “Tom Eisner — An Incorrigible Entomophile and Innovator Par Excellence,” at the awards breakfast on Tuesday, Nov. 19.
ESA officials selected Leal, an ESA fellow and internationally recognized chemical ecologist, for the global honor. Leal is the first UC Davis scientist selected to present the Founders' Memorial Lecture, although medical entomologist Shirley Luckhart of the University of Idaho, formerly of UC Davis, delivered the lecture in 2018.
The 7000-member ESA is the world's largest organization serving the professional and scientific needs of entomologists and people in related disciplines. ESA, founded in 1889, is headquartered in Annapolis, Md.
What are bolas spiders? Well, they're also known as angling or fishing spiders. That's because they don't spin a web, they hunt with a sticky glob of silk on the end of a line known as "bolas."
When they swing the bolas or lines at flying moths, they snag their prey, much like an angler snags a fish on a hook. Fish on? Bug on!
And are you ready for a "Buggy Scene?"
Walter Leal, a distinguished professor with the Department of Molecular and Cellular Biology and a past chair of the UC Davis Department of Entomology, is featured on the College of Biological Sciences website in a piece titled "Discovering Curiosity: the Buggy Scene of Desire with Distinguished Professor Walter Leal."
The article, by communications specialist Greg Watry, begins with Leal watching a bolas spider snag a moth.
"The American bolas spider is no one-trick pony when it comes to its enticing chemical mimicry," Watry wrote. "As midnight approaches, bristly cutworms retreat and smoky tetanolita moths (Tetanolita mynesalis) appear, the two moth species active during different times of the night. The American bolas spider can chemically compensate for the moths' different schedules, shifting the makeup of its deadly bouquet to match the pheromones produced by a female smoky tetanolita."
"Basically, we are bolas spiders,” Leal related. Read the article here.
Leal, a native of Brazil, holds a master's degree and doctorate from Japan, where he studied insect chemical communication and olfaction, and held the position of senior research scientist in Japan's Ministry of Agriculture, the first non-Japanese scientist to do so. He joined the UC Davis faculty in 2000 and was named chair of the Department of Entomology (now the Department of Entomology and Nematology) in 2006.
Leal is internationally known for his chemical ecology research--he and his lab have identified sex pheromones of many insects, including moths, beetles, cockroaches and mites. His work is especially important in the field of agriculture, as he targets pests that eat our crops. His pheromones attract pests just as bolas spiders attract moths.
"Leal studies the molecular basis of insect olfaction, unraveling how insects detect chemicals and using that knowledge to inform pest management techniques," Watry wrote. "Most recently, he and colleagues identified a sex pheromone of the Asian citrus psyllid (Diaphorina ciri), a worldwide threat to the citrus industry that made its way to California in 2008. Identifying the pheromone could help mitigate the agricultural devastation caused by the insects."
On a side note, Leal is known for his leadership: he co-chaired the 2016 International Congress of Entomology, the largest scientific event in the history of entomology and he will deliver the Founders' Memorial Lecture at the 2019 Entomological Society of America meeting in St. Louis, Mo., on pioneer chemical ecologist Thomas Eisner, 1929-2011. Eiser is commonly regarded as the "father of chemical ecology" for his discoveries elucidating chemical defenses used by insects.
Leal is also known as an exemplary, innovative and caring teacher who seeks opportunities for their success. He was the one who brought Science without Borders (SwB) to the UC Davis campus, which resulted in many students and visitors to UC Davis laboratories.
"Really nice professor who cares about his students' future," wrote a student on Rate My Professors. "He has guest speakers from industry talk to the class and Dr. Leal always makes sure to ask them about internships and ways to get our foot in the door."
Leal recently returned from his native Brazil where UC Davis Global Affairs asked him if he would meet with the leadership of São Paulo State University to explore possible collaborations. He did, and plans are in the works. Stay tuned!
Breaking news and a well-deserved honor:
Insect chemical ecologist Walter Leal, a distinguished professor at the University of California Davis, has just been selected to deliver the Founders' Memorial Award Lecture at the Entomological Society of America (ESA) meeting, to be held Nov. 17-20 in St. Louis, Mo.
Leal, a distinguished professor in the Department of Molecular and Cellular Biology and a former chair of the Department of Entomology (now the Department of Entomology and Nematology), is known as a exemplary scientist, teacher and leader. He will discuss the work of insect chemical ecologist Thomas Eisner (1929-2011), widely known as "the father of chemical ecology."
Leal will present his talk, titled "Tom Eisner--An Incorrigible Entomophile and Innovator Par Excellence," at the Entomology 2019 awards breakfast, which begins at 7:30 on Tuesday, Nov. 19.
“I am absolutely delighted to have the opportunity to honor Tom Eisner--one of the founding fathers of chemical ecology,” Leal told us today. “And, consequently, Tom's main collaborator, the late Professor Jerry Meinwald--my role model, mentor and friend of three decades.”
Leal investigates the molecular basis of olfaction in insects and insect chemical communication. (See the Leal lab's work on DEET in Entomology Today.) He researches environmentally friendly alternatives to control insects of medical importance, and also targets agricultural pests.
Leal is the first UC Davis scientist selected to present the Founders' Memorial Lecture, although medical entomologist Shirley Luckhart of the University of Idaho, formerly of UC Davis, delivered the lecture in 2018. In her lecture, "He Gave to Man Control Over That Dreadful Scourge, Yellow Fever," she honored Walter Reed (1851-1902), the U.S. Army physician who in 1901 led a team of researchers that linked the spread of yellow fever to mosquitoes.
ESA established the Founders' Memorial Award in 1958 to honor the memory of scientists who made outstanding contributions to entomology.
Thomas is known for his discoveries on chemical defenses used by insects against predators. “Notable among them was deciphering how the bombardier beetle defends itself with an internal exothermic chemical reaction, explosively sprayed at attackers,” according to a press release by Joe Rominiecki, ESA communications manager. “That discovery topped a lengthy list of revelations about the complex and often surprising biochemicals insects produce, from the bitter, predator-deterring taste of the cochineal scale's brilliant red pigment to the sticky foot secretions that allow the palmetto beetle to cling so tightly to leaf surfaces. “
A native of Brazil and educated in Brazil and Japan, Leal received his master's degree and doctorate in Japan: his master's degree at Mie University in 1987, and his doctorate in applied biochemistry at Tsukuba University in 1990. Leal then conducted research for 10 years at Japan's National Institute of Sericultural and Entomological Science and the Japan Science and Technology Agency before joining the faculty of the UC Davis Department of Entomology in 2000.
Leal co-chaired the 2016 International Congress of Entomology (ICE), themed "Entomology Without Borders." The event, held in Orlando, Fla,. drew the largest delegation of scientists and experts in the history of the discipline. That would be 6682 attendees from 102 countries.
Among his many honors, Leal is a fellow of three organizations--ESA, the American Association for the Advancement of Science, and the California Academy of Sciences--and an honorary fellow of the Royal Entomological Society. He received a silver medal from the International Society of Chemical Ecology. Another honor: he was inducted into the Brazilian Academy of Sciences.
“Walter is an amazing person and an amazing scientist,” said Fred Gould, distinguished professor in the Department of Entomology and Plant Pathology at North Carolina State University. “His work has opened new doors to the understanding of how insects receive and perceive odors and has saved farmers in California and Brazil more than $100 million. He's at a point where he could sit back and bask in the glory of his accomplishments, but that is not Walter. He remains as prolific as ever.”
"Walter's lecture promises to be outstanding," said colleague James R. Carey, UC Davis distinguished professor of entomology and a fellow of ESA who received the organization's national distinguished teaching award. "He is known as one of the exceptional, truly elite, instructors at UC Davis and beyond." Carey praised Leal's "innovation in content delivery, engagement with his audience, his ability to inspire and motivate them, and his always-clever touches of humor."
ESA, founded in 1889, is the world's largest organization serving the professional and scientific needs of entomologists and people in related disciplines. Its members, now more than 7000, are affiliated with educational institutions, health agencies, private industry, and government. Headquartered in Annapolis, Maryland, the Society stands ready as a non-partisan scientific and educational resource for all insect-related topics.
The ESA meeting in St. Louis is expected to bring together approximately 3,000 insect scientists to share their latest research and communicate the global science of entomology, Rominiecki said.
More than 2000 scientists are registered to attend the meeting, to be held Sept. 2-6 in Gramado, Brazil.
UC Davis scientists delivering plenary addresses will be Frank Zalom, distinguished professor of entomology, UC Davis Department of Entomology and Nematology and a past president of the Entomological Society of America (ESA); Walter Leal, distinguished professor, UC Davis Department of Molecular and Cellular Biology, and a past chair of the Department of Entomology and Nematology; and Joanna Chiu, associate professor and vice chair, UC Davis Department of Entomology and Nematology. More than 2000 attendees are registered.
On behalf of ESA, Zalom is co-organizing and co-chairing a joint conference with Antonio Panizzi, a past president and international delegate of the Entomological Society of Brazil. That event, to take place the day before the XXVII Congresso Brasileiro and X Congresso Latino-Americano meeting, will involve developing a “Grand Challenge Agenda for Entomology in South America.
Zalom will speak on “The American Experience with the Grand Challenge Agenda in Entomology.” In addition, ESA president Michael Parrella, dean of the College of Agricultural and Life Sciences at the University of Idaho and a former chair of the UC Davis Department of Entomology and Nematology, will provide an update on the 2018 ESA annual meeting, set Nov. 11-14 in Vancouver, B. C. Speakers also will include the presidents of the entomological societies of Argentina, Peru and Brazil.
Leal, a native of Brazil, will present the opening lecture of the joint conference of the XXVII Brazilian Congress and X Latin American Congress of Entomology on “Insect Vectors: Science with Applications in Agriculture and Medicine,” on Sunday, Sept. 2. This will be his fourth opening lecture—a record—at the Brazilian Congresses of Entomology (2004 in Gramado; 2008 in Uberlandia; and 2014 in Goiania). As an aside, legendary entomologist Marcos Kogan previously held the record: he presented two opening lectures, one in 1983 and another in 2002. Both Leal and Kogan (professor emeritus of agricultural entomology, University of Illinois and professor emeritus, Oregon State University) were elected ESA fellows; Leal in 2009 and Kogan in 2016. Zalom received the honor in 2008.
Zalom, an integrated pest management specialist, and former director of the UC Statewide Integrated Pest Management Program (UC IPM) and Chiu, who specializes in molecular genetics of animal behavior, will speak on their research at the joint meeting. Zalom will deliver a plenary address on “Drosophila suzukii in the United States” on Sept. 5, and Chiu will keynote a symposium on Sept. 3; her lecture is titled “Circadian Clock Research Applied to Agriculture and Public Health.” She will give a second lecture: "Drosophila as an Insect Model" on Sept. 3.
The spotted wing drosophila (SWD) is a serious pest of fruit crops. Most drosophila flies feed on spoiled fruits, but SWD prefers fresh fruit (berries and soft-skinned fruits). Read more about SWD on the UC IPM website.