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.
You've probably watched those colorful painted ladies (Vanessa cardui) fluttering about in your yard, but have you read the newly published research about their wing color patterns and genetic codes?
In researching the color patterns and the genes responsible for those patterns, biologists Jeffrey Marcus and Roohollah Abbasi of the University of Manitoba, Winnipeg, Canada, found a previously undetected compartment boundary that may exist in all holometabolous insects. (Holometabolism, also called complete metamorphism, is a form of insect development that includes four stages: egg, larva, pupa and adult.)
Scientists have long known that in the common fruit fly, Drosophila melanogaster, the forewing is divided into two developmental compartments, but this newly published research in Scientific Reports, A New A-P Compartment Boundary and Organizer in Holometabolous Insect Wings, is a real eye-opener.
Writer Viviane Callier of Washington, D.C., a trained insect physiologist, wrote about the research in the Nov. 30th edition of Entomology Today, published by the Entomological Society of America.
In her piece, "Butterfly Color Patterns Reveal Clues About the Genes that Build Insect Wings," Callier described butterfly wings as "natural canvases decorated with elaborate color patterns," but noted that "how these patterns develop and evolve is still incompletely understood. Now, a new study in Scientific Reports (Nature.com) has identified the genetic code by which butterflies can assign color patterns to different parts of their wings during development. The code is based on a set of genes called transcription factors that establish compartments in most—perhaps all—insect wings. Each compartment, whose 'address' is determined by the combination of genes that are active in that sector of the wing, can evolve different color patterns independently from the other compartments."
Marcus and Abbasi explained in their abstract:
"Decades of research on the highly modified wings of Drosophila melanogaster has suggested that insect wings are divided into two Anterior-Posterior (A-P) compartments separated by an axis of symmetry. This axis of symmetry is created by a developmental organizer that establishes symmetrical patterns of gene expression that in turn pattern the A-P axis of the wing. Butterflies possess more typical insect wings and butterfly wing colour patterns provide many landmarks for studies of wing structure and development. Using eyespot colour pattern variation in Vanessa butterflies, here we show an additional A-P axis of symmetry running between wing sectors 3 and 4. Boundaries of Drosophila mitotic clones suggest the existence of a previously undetected Far-Posterior (F-P) compartment boundary that coincides with this additional A-P axis. A similar compartment boundary is evident in butterfly mosaic gynandromorphs. We suggest that this additional compartment boundary and its associated developmental organizer create an axis of wing colour pattern symmetry and a gene expression-based combinatorial code, permitting each insect wing compartment to acquire a unique identity and allowing for the individuation of butterfly eyespots."
The research "bears on some of our T-shock experiments back in the 70s-80s," observed Art Shapiro, distinguished professor of evolution and ecology when asked if he'd read the research paper. Yes. He wrote a chapter, The Genetics of Seasonal Polyphenism and the Evolution of 'General Purpose Genotypes' in Butterflies' in the Klaus Wöhrmann/Volker Loeschcke book, Population Biology and Evolution. You can read it online.
In his abstract, Shapiro, who has studied and monitored butterflies for more than four decades and maintains a website, Art's Butterfly World, points out that his Genetics of Seasonal Polyphenism chapter "is really a specialized appendix to Professor Scharloo's on 'The Genetics of Adaptive Reactions.' It deals with a particular set of such reactions — those of butterfly wing patterns to environmental factors — and asks whether those which seem adaptive are evolutionarily related to those which do not, and if so, how. Despite more than a century of interest in such phenomena, the answers are not yet in; we are only now able to do the carefully controlled experiments necessary to partition phenotypic variation into its environmental and genetic components and this work is still very much in progress. So this will be a very unsatisfying presentation — full of qualitative statements, long on speculation, short on hard data. If it serves as a provocation it will have done its duty."
Shapiro goes on to say that "a glance through any butterfly book of the coffee table variety reveals an astonishing diversity of patterns. The fact is that we have only the remotest idea of the functional significance of any of them, as we were recently reminded by Silberglied et al. (1980). One reason is that bewildering diversity which defies rational classification; another is that it is almost impossible to relate a pattern to an ecological and behavioral context when observing a specimen set on a pin."
All the more reason to marvel at the stunning diversity of butterflies that grace our yards. Or what Viviane Callier so eloquently described as "natural canvases decorated with elaborate color patterns."
The brown planthopper, Nilaparvata lugens, or BPH, is the economically most important rice pest in Asia. It's found only in southeast Asia and Australia, but the methods that a nine-member research team used may be appropriate here in the rice-growing areas of California, says UC Davis agricultural entomologist Christian Nansen, who was part of a nine-member team that just published first-of-its-kind research. It appears in Scientific Reports of the journal Nature.
Using the sustainable pest management method known as "the banker plant system," they did field and laboratory work in China with good results: attracting alternative hosts to parasitoids of rice insect pests, can help protect a rice crop. The players: a grass species, a planthopper, and an egg parasitoid.
Research results showed that BPH densities were significantly lower in the rice fields with the sustainable pest management practice known as the banker plant system compared to control rice fields without the banker plant system, the scientists said.
“Many people are familiar with the concept of a ‘trap crop'-- a sacrificial crop which is planted mixed in with or adjacent to an economically important crop and the trap crop serves to manipulate pests away by offering them a more attractive/suitable host alternative,” said Nansen, an assistant professor with the UC Davis Department of Entomology and Nematology. “The use of banker plants in pest management is similar to the use of trap crops, but banker plants typically have multiple ecological functions.”
The researchers planted a grass species, Leersia sayanuka, next to rice. It attracted a planthopper (Nilaparvata muiri), which does not infest rice.
Rice is the stable food of more than 50 percent of the global population, and 60 percent of the Chinese population. However, scientists concur that the world's rice production needs to increase drastically over the next three decades to meet the growing food demand in Asia. Growing concern over BPH outbreaks and higher pesticide usage led to the sustainable pest management study.
Titled “Use of Banker Plant System for Sustainable Management of the Most Important Insect Pest in Rice Fields in China,” the research is unique in that it is the first published study describing the attraction of alternative hosts to parasitoids of rice insect pests. In rice systems, previously published research involved planting sesame as a nectar source to promote the establishment and persistence of a predatory bug; and studies involving parasitoids.
BPH feeds on the rice crop at all stages of plant growth and can also transmit two viruses, rice ragged stunt virus, and rice grassy stunt virus. Damage can commonly result in a 60 percent yield loss. An infestation is often called “hopper burn,” referring to yellow patches that soon turn brown.
Noting the importance of the banker plant system, Nansen said that banker plants “involve promotion of plant diversity to enhance pest self-regulatory ecosystem functions, such as predation and competition, to reduce susceptibility of agricultural crops to native and invasive pests. Also, banker plants “may provide resources, such as shelter, pollen and nectar or alternative preys to improve the establishment and persistence of beneficial insect populations used to control a specific pest.” The first successful banker plant system, developed in 1977, involved tomato as the banker plant, a parasitoid and a whitefly.
Nansen is affiliated with both UC Davis and the Zhejiang Sustainable Pest and Disease Control, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China.
Co-authors of the research paper include lead author Zhongxian Lu and colleagues Xusong Zheng, Yanhui Lu, Junce Tian, Hongxing Xu, all of the Zhejiang Sustainable Pest and Disease Control; and Pingyang Zhu, Facheng Zhang and Guihua Chen of the Jinhua (China) Plant Protection Station.
The study was jointly supported by the National Key Research and Development Program of China, Zhejiang Key Research and Development Program, and the Special Fund for Agro-scientific Research in the Public Interest.
Good news: The first day of spring.
Bad news: The future of the Eastern, migratory population of the monarch butterflies.
Research published today in Scientific Reports indicates there's a "quasi-extinction risk" for the Eastern, migratory population of monarch butterflies (Danaus plexippus).
A nine-member team, led by Brice X. Semmens of the Scripps Institution of Oceanography, UC San Diego, noted that the Eastern, migratory population has declined by more than 80 percent over the last decade. "The monarch's multi-generational migration between overwintering grounds in central Mexico and the summer breeding grounds in the northern U.S. and southern Canada is celebrated in all three countries and creates shared management responsibilities across North America," they wrote in their abstract.
"...We find that, given a range of plausible quasi-extinction thresholds, the population has a substantial probability of quasi-extinction, from 11–57 percent over 20 years, although uncertainty in these estimates is large."
The world population of monarchs dipped from 1 billion in the mid-1990s to about 150 million monarchs today, estimates show. The authors noted that "the vast majority of the remaining monarchs live in the eastern portions of Canada, the United States and Mexico."
The researchers blamed the loss of breeding habitat as the major cause for the decrease in the United States.
Monarch lay their eggs only on milkweed, and caterpillars eat only milkweed. Other threats: habitat loss in the Mexican overwintering sites, climate change, insecticides, mowing regimes, invasive species, and diseases.
What to do? There's a movement afoot to place the monarch on the Fish and Wildlife Service's threatened or endangered species list.
Meanwhile, the key solution is to create and restore monarch breeding habitat, the researchers said.
It would be a shame to lose the mighty monarch.