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)
Insects--their beauty, their structure, their diversity--are inspiring noted fashion designers, but those fashion designers are way, way behind the UC Davis Entomology Graduate Students' Association (EGSA).
EGSA members are graduate student totally into bugs. They study them, research them and wear them. And yes, some do eat them. Can you say "chocolate chirp cookies? (made with cricket flour)?"
Every year EGSA conducts a t-shirt contest and the faculty, staff and students pick the winner. The good news is that the t-shirts--past and present--are for sale all year around, but folks take a special interest in them during the holiday season. Stocking stuffers!
The Beatles? Think The Beetles.
Instead of the English rock band John Lennon, Paul McCartney, George Harrison and Ringo Star crossing Abbey Road in single file (that's the iconic image on the cover of their album, Abbey Road), think of The Beetles (four insects) crossing Abbey Road in single file. Beneath the images of the beetles are their family names: Phengogidae, Curculionidae, Cerambycidae and Scarabaeidae. Think glowworm, snout, long-horned, and scarab beetles.
If you're not partial to beetles, how about honey bees, wasps, and "Entomology's Most Wanted?"
You're in luck.
"This year we are discounting some of our old designs from $15 to $10!" announced the officers, headed by Ph.D student and ant specialist Brendon Boudinot of the Phil Ward lab. "Order by Dec. 15th for delivery within the United States by the 23rd. If you are on campus and would like to pick up the shirt instead, please do not pay for shipping online and email Emily Bick at firstname.lastname@example.org (of the Christian Nansen lab) to schedule pick up. The online store will close on Dec. 17th until early January." The prices range from $10 to $15 to $17. Access their online store: https://mkt.com/UCDavisEntGrad/
It's for a good cause: helping the graduate students. The added bonus, you get to "bug" your friends, family and colleagues when you wear these t-shirts.
You never know what you'll find when you visit a pollinator garden.
Take the case of our visit Nov. 12 to the Sonoma Cornerstone, Sonoma, to see the pollinator garden of Kate Frey, an ardent pollinator advocate, world-class garden designer, and co-author of The Bee Friendly Garden with UC San Francisco professor Gretchen LeBuhn.
The flower-filled Frey garden is a people/pollinator favorite at the Sonoma Cornerstone, and no wonder.
We spotted a yellow-faced queen bumble bee, Bombus vosnesenskii, foraging on Salvia Indigo spires. Normally, you don't see bumble bees this time of year, but this one came out of hibernation temporarily to eat. She appeared famished!
Bombus vosnesenskii is among the bees featured in the University of California-authored book, California Bees and Blooms: A Guide for Gardeners and Naturalists (Heyday Press). It's the work of entomologists Gordon Frankie of UC Berkeley and Robbin Thorp of UC Davis, entomologist/photographer Rollin Coville and plant expert Barbara Ertter of UC Berkeley. Thorp, a UC Davis distinguished emeritus professor, also co-authored Bumble Bees of North America: An Identification Guide (Princeton University).
In their book, California Bees and Blooms, the authors call attention to this iconic Bombus species: the yellow hairs on the face and top of head, and the yellow stripe on the abdomen.
Hibernating queen bumble bees are a joy to photograph as they forage for food, buzzing from blossom to blossom to sip nectar. This one seemed to be braking during a winter break.
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."
See those red spots on your milkweed seed pods?
Lady beetles (aka ladybugs or "garden heroes") are feasting on aphids.
And they're having a ball.
We've been watching the critters on our milkweed, Gomphocarpus physocarpus, for the last couple of months. The plant is a favorite among monarch butterflies, florists and interior decorators. This is the host plant of the monarchs; caterpillars eat only milkweed. It's also a "hostess" plant; florists add them to their floral bouquets and interior decorators grace their holiday tables with them. In fact, interior decorator Allison Domonoske of South Carolina transformed the White House Thanksgiving tablescape with moss, driftwood, pine cones, little white pumpkins and what she called "balloon-plant milkweed: large, green, ball-like flowers."
That was them!
We call them "lime green ball-like pods, covered with tiny spiny hairs"--or you could call them "spiky seed pods," as the Washington Post did. At any rate, they're often used for decorating.
Hmm, a forest green Douglas Fir Christmas tree adorned with lime green spiky seed pods? With red bows amid the green boughs? Gomphocarpus physocarpus to the rescue!
According to the Master Gardener Program, "the name physocarpa comes from the Greek physa meaning bladder and karpos, fruit, referring to the inflated, bladder-like fruits. It has a plethora of common names including balloon plant, balloon cotton-bush, balloon milkweed, bishop's balls, elephant balls, hairy balls, monkey balls, swan plant, and many others." It's also known as goose plant, giant swan milkweed, family jewels, Oscar, and by its former botanical name, Asclepias physocarpa.
It's a tall, spectacular plant that can reach a height of an NBA All-Star. Last summer monarch butterflies laid their eggs on it, lady beetles kept the aphids off it, and praying mantids kept everything off, including bees, butterflies and beetles.
If you have some growing in your garden, think holiday decorations...minus the red lady beetles, the First Ladies of the Garden, and their prey.