Newly published research by an international team of scientists, including UC Davis entomologist and co-author Diane Ullman, promises to be an important resource on the genome analysis of the western flower thrips, an invasive global agricultural pest that feeds on plants and is considered a supervector, spreading plant viruses. 

 The article, “Genome-Enabled Insights into the Biology of Thrips as Crop Pests,” is published in the journal BMC Biology. It is the work of 57 scientists on five continents. 

“This project represents over eight years of work by at least 17 laboratories across the globe,” said Professor Ullman, a former chair of the entomology department and a fellow of the Entomological Society of America and the American Association for the Advancement of Science. Her laboratory worked closely with project leader and first author Dorith Rotenberg of North Carolina State University. Project scientist Sulley Ben-Mahmoud of the Ullman lab is the paper's third author. 

The western flower thrips, Frankliniella occidentalis, causes billions of dollars a year in damage worldwide.   Native to Western North America and about the size of a pinhead, the insect feeds on a wide array of food, fiber, and ornamental crops and transmits plant viruses that cause significant economic damage. 

“The western flower thrips and the viruses it transmits, including tomato spotted wilt virus, is important to California agriculture, causing serious problems for tomato growers, pepper growers and growers of leafy greens,” Ullman said. The tomato spotted wilt virus infects more than 1000 plant species, ranging from tomatoes, tobacco and peanuts to pansies and chrysanthemums. 

 “This system has been a central element of my research program for over 30 years," Ullman said, "and I am extremely excited to see this important resource made available as a tool to help us understand and control these important pests.” 

 In their abstract, the authors wrote that the publication should lead to “understanding the underlying genetic mechanisms of the processes governing thrips pest and vector biology, feeding behaviors, ecology, and insecticide resistance.”   

This is the first genome sequence and analysis for a member of the Thysanoptera, an order that contains more than 7,000 species of small insects with fringed wings. 

“Attaining a tool to unlock the mysteries of western flower thrips biology and interactions with plant viruses in the family Tospoviridae has been a dream of mine through over 30 years of working on this system,” Ullman commented.  “The genome project enabled the discovery of salivary gland-enriched genes in this tiny insect that is now guiding work that Sulley Ben-Mahmoud and I are doing with collaborators Dorith Rotenberg, Joshua Benoit, Samuel Bailey and Priya Rajarapu to identify salivary proteins acting as effectors.” 

Rotenberg launched the project in 2011 after delivering a lecture at the 5th Annual Arthropod Genomics Symposium in Kansas City, Mo. “At the time, I was very naïve about what it would take to steward a thrips genome project, but was excited about what a genome sequence could mean for those of us interested in the molecular basis of thrips vector competence and thrips pest biology.” 

The team worked with the i5k initiative, an international effort to sequence and analyze 5,000 arthropod genomes. This includes insects, crustaceans, spiders and other creatures with exoskeletons, segmented bodies and pairs of jointed legs. 

The Rotenberg-led thrips genome project team first developed an inbred line of thrips. Baylor College of Medicine's Human Genome Sequencing Center sequenced and assembled the genome.  The Rotenberg team then verified the location of 10 percent of the nearly 17,000 genes and annotated them to better understand what they do. 

The authors report that some genes are associated with the thrips' ability to develop and reproduce, to find plant hosts through taste and smell,  to protect against pathogens, and to detoxify plant-produced chemicals and insecticides. The latter is of special interest because thrips are known for rapidly building up resistance to chemicals. 

Said Rotenberg: “I discovered over the course of eight years that the thrips genome consortium created something much greater than the sum of its parts. I was fortunate to recruit 17 international groups with expertise in arthropod genomics, evolution and development, thrips vector biology and microbe (and virus)-insect interactions to volunteer their time not only to manually correcting and annotating gene models, but to use expression evidence to explore with me new frontiers in thrips innate immunity, lateral gene transfers of bacterial origin, thrips-plant interactions, thrips development and reproduction.  These world-renowned experts helped shape the landscape for contemporary molecular and evolutionary studies of Thysanoptera and in my opinion, as  important, helped shape the careers of several undergraduates, grad students and postdoctoral scholars involved in the process. I am excited and proud of what we accomplished together.”

Ben-Mahmoud described the research as “a monumental feat, and I am proud of my contributions to it. I have no doubt that the paper will inform and benefit the studies of many other international insect-vector research groups, not only those who work directly with the western flower thrips.” 

Mosquito researcher Maria Onyango, a postdoctoral associate at the New York State Department of Health,  Albany, N.Y., will deliver a virtual seminar hosted by the UC Davis Department of Entomology and Nematology on Wednesday, Oct. 21 on "The Impact of Zika Virus Infection on the Metabolites and Microbiome of Aedes albopictus."

The Zoom seminar, open to all interested persons, will take place from 4:10 to 5 p.m. Click here for the form to obtain the Zoom link to connect.

"In this talk, we are going to demonstrate the tripartite interactions between the microbiome, mosquitoes of the genus Aedes and Zika virus that they transmit," she says. Aedes albopictus is also known as the Asian tiger mosquito.

"My research focuses on the tripartite interactions between the microbiome, mosquitoes as vectors and the arboviruses they transmit," Onyango says. "In addition, I am interested in the role the vector-host- pathogen interface plays in enhancing disease severity in the vertebrate host. The goal of my research is to develop innovative control mechanisms both for the vector and pathogens they transmit."

Host is medical entomologist-geneticist Geoffrey Attardo, assistant professor, UC Davis Department of Entomology and Nematology. Cooperative Extension specialist and assistant professor Ian Grettenberger coordinates the fall seminars.

"Dr. Maria Onyango works on the biology underlying interactions between arboviruses (Zika virus), vector mosquitoes and the associated microbiome," Attardo said.

Along with seven other scientists, Attardo and Onyango co-authored a research article in the Oct. 2nd edition of Frontiers in Microbiology on"Zika Virus Infection Results in Biochemical Changes Associated With RNA Editing, Inflammatory and Antiviral Responses in Aedes albopictus."

The abstract:

"Rapid and significant range expansion of both the Zika virus (ZIKV) and its Aedes vector species has resulted in the declaration of ZIKV as a global health threat. Successful transmission of ZIKV by its vector requires a complex series of interactions between these entities including the establishment, replication and dissemination of the virus within the mosquito. The metabolic conditions within the mosquito tissues play a critical role in mediating the crucial processes of viral infection and replication and represent targets for prevention of virus transmission. In this study, we carried out a comprehensive metabolomic phenotyping of ZIKV infected and uninfected Ae. albopictus by untargeted analysis of primary metabolites, lipids and biogenic amines. We performed a comparative metabolomic study of infection state with the aim of understanding the biochemical changes resulting from the interaction between the ZIKV and its vector. We have demonstrated that ZIKV infection results in changes to the cellular metabolic environment including a significant enrichment of inosine and pseudo-uridine  levels which may be associated with RNA editing activity. In addition, infected mosquitoes demonstrate a hypoglycemic phenotype and show significant increases in the abundance of metabolites such as prostaglandin H2, leukotriene D4 and protoporphyrinogen IX which are associated with antiviral activity. These provide a basis for understanding the biochemical response to ZIKV infection and pathology in the vector. Future mechanistic studies targeting these ZIKV infection responsive metabolites and their associated biosynthetic pathways can provide inroads to identification of mosquito antiviral responses with infection blocking potential."

Onyango holds two degrees from the University of Nairobi, Kenya: a bachelor of science degree in biochemistry and zoology and a master's degree in applied parasitology. She received her doctorate in veterinary entomology from Deakin University and Australian Animal Health Laboratory, Commonwealth Scientific and Industrial Research Organisation (CSIRO), and then completed postdoctoral training at the Yale School of Public Health, Department of Epidemiology of Microbial Diseases. 

For any technical issues regarding the seminar, contact Grettenberger at imgrettenberger@ucdavis.edu

Want to learn more about arthropods in rice and alfalfa fields and the UC Davis research underway to help the agriculturists?

Cooperative Extension agricultural specialist Ian Grettenberger, assistant professor, UC Davis Department of Entomology and Nematology, and his graduate student, Madison "Madi" Hendrick, will discuss the crops, the pests, and the natural enemies or beneficials at a virtual Facebook live session from 11 a.m. to noon, Thursday, Oct 22.

The event, "The Good and the Bad: Insects and Other Arthropods in Agriculture, with a Focus on California Rice and Alfalfa," will be live-streamed on the UC Davis Bohart Museum of Entomology's Facebook page. (Link to Facebook live here). Grettenberger and Hendrick will present short talks and then field questions.  No personal Facebook account is required to join the session, which is free and open to the public.

"This is all about the arthropods, both the pests and beneficials that they study in the rice and alfalfa fields," said Tabatha Yang, education and outreach coordinator for the Bohart Museum of Entomology. "Most of the focus is on insects, but tadpole shrimp in rice fields also will be discussed." A virtual family craft activity is also planned.

"I will be discussing some of the insect (or arthropod) problems faced by growers of rice in California and some of the challenges in managing them, Grettenberger said. "In rice, some of the key arthropod pests are tadpole shrimp, which can turn what would have been a lush stand if rice into a poor stand with a lot of floating seedlings. Meanwhile, later in the year, armyworm caterpillars, the larvae of a moth, can chew on rice leaves and destroy plants. I'll discuss some of the ongoing work to better understand and manage these pests."

Grettenberg's fields of expertise include field and vegetable crops; integrated pest management; applied insect ecology, and biological control of pests. (See Spotlight on Ian Grettenberger.) Among his current grants:

• Protection of rice from invertebrate pests
• Insecticide resistant alfalfa weevils in the western United States: Quantifying the scope of resistance and implementing a plan to manage the threat​
• Management of key cotton arthropod pests with insecticides and acaricides, a proactive approach to prepare for the invasion of the tomato leafminer (Tuta absoluta)  into California
• Detection, biology and control of the exotic Swede midge (Contarinia nasturtii) for California cole crops
• Management of the western spotted and striped cucumber beetle in melon production
• Biological control of the bagrada bug
• Insecticide resistance monitoring and evaluation of efficacy of current chemical tactics for managing aphids and thrips in lettuce

Grettenberger joined the UC Davis Department of Entomology and Nematology in January 2019. Grettenberger, who fills the vacated position of Larry Godfrey (1956-2007), received his bachelor of science degree in biology, with an ecology, evolution and organismal emphasis (honors program) in 2009 from Western Washington University, Bellingham, Wash., and his doctorate in entomology in 2015 from Pennsylvania State University, State College, Pa. He served as a postdoctoral researcher in the Godfrey lab and later, the Frank Zalom lab, before accepting his current appointment of assistant Cooperative Extension specialist.

What sparked his interest in entomology? "I had biologist parents, and was drawn into entomology at a pretty young age," Grettenberger said. "I spent plenty of time looking in flowers and turning over logs looking for insects. Once I started thinking about going to graduate school for entomology, I decided to focus on the intersection of agricultural entomology and insect ecology. I wanted to work on applied issues in entomology."

Hendrick, a second-year graduate student in the Grettenberger lab, received her bachelor's degree in iInternational studies at North Carolina State University, and also spent a semester at Nagoya University in Japan (she minored in Japanese).

"I got my start in entomology completely by chance!," Hendrick related. "I needed a science credit and happened to pick a class called 'Insects and People.”' That class really helped me to reframe the way I thought about insects and appreciate what interesting little critters they are. Through that class, I was also able to get a job as an undergraduate assistant in an entomology lab. I worked in a specialty crops lab, where I developed interests in integrated pest management and invasive species. I now study insecticide resistance in the alfalfa weevil, and I'm excited to share what I've learned through this outreach event!"

Grettenberger, Yolo County Farm Advisor Rachael Freeman Long and Madi Hendrick recently wrote a piece in the UC Agricultural and Natural Resources (UC ANR) blog, Alfalfa and Forage News, "A (Virtual )Update on Worms, Weevils an Aphids in Alfalfa."

"This year, the Kearney Research and Extension Center Alfalfa and Forage Field Day went virtual," Grettenberger wrote. "Attendees did not get the chance to look out over lush fields of alfalfa or towering plantings of sorghum, but they get did an update on ongoing work in alfalfa and other forages. Our team put together a rapid-fire video to discuss what are typically the key insect pests in California alfalfa: summer worms, alfalfa weevils, and aphids."

The summer worms in alfalfa include the summer worms: Western yellowstriped armyworm, beet armyworm and alfalfa caterpillar. Another key pest is the alfalfa weevil. The trio also discussed  aphids and their natural enemies, including lady beetles, aka ladybugs).

Pests of rice include armyworms, aster leafhoppers, crayfish, rice leafminers, rice seed midges, rice water weevils and tadpole shrimp.

The Bohart Museum, directed by Lynn Kimsey, UC Davis professor of entomology, is located in Room 1124 of the Academic Surge Building on Crocker Lane, UC Davis campus, but is temporarily closed. The museum houses nearly eight million insect specimens; a live "petting zoo" of Madagascar hissing cockroaches, walking sticks and taranatulas; and a gift shop stocked with insect-themed T-shirts, books, posters, jewelry, candy and insect-collecting equipment. 

More information on the Bohart Museum's virtual presentation is available on its website or by contacting Yang at tabyang@ucdavis.edu.

Resources: 

• Alfalfa and Forage News: A (Virtual) Update on Worms, Weevils and Aphids in Alfalfa (By Ian Grettenberger, Rachael Freeman Long and Madi Hendrick, Sept. 20, 2020) (See video on same page)
• Alfalfa and Forage News: Natural Enemies Are Important for Control of the Aphid Complex in Alfalfa--A Case Study (By Ian Grettenberger, Rachael Freeman Long, Daniel Putnam and Rob Wilson, April 7, 2020)
• UC Statewide Integrated Pest Management Program: How to Manage Pests of Alfalfa
• UC Statewide Integrated Pest Management Program: Insects and Other Pests of Rice

 

Natural landscapes surrounding vineyards can decrease pest outbreaks and depress pesticide use, according to a UC Davis paper published in the current edition of the journal Ecology Letters.

A five-member team led by postdoctoral researcher Daniel “Dani” Paredes of the Daniel Karp lab, UC Davis Department of Wildlife, Fish and Conservation Biology (WFCB), analyzed a 13-year government database to assess how the landscapes surrounding 400 Spanish vineyards influenced European grapevine moth (Lobesia botrana) outbreaks and insecticides application rates.

The article, "Landscape Simplification Increases Vineyard Pest Outbreaks and Insecticide Use," is now online.  

“At harvest, we found pest outbreaks increased four-fold in simplified, vineyard-dominated landscapes compared to complex landscapes in which vineyards are surrounded by semi-natural habitats,” said lead author Paredes, who holds a doctorate in environmental sciences (2014) from the University of Granada, Spain.  “Overall, our results suggest that simplified landscapes increase vineyard pest outbreaks and escalate insecticide spray frequencies. In contrast, vineyards surrounded by more productive habitats and more shrubland area are less likely to apply insecticides.”

Landscapes around farms are rarely managed to suppress damaging crop pests, partially because researchers rarely measure the key variables that drive farming decisions. This paper, however “shows how using really huge datasets—in this case generated by government employees working with farmers in Spain--can reveal how natural habitats surrounding agriculture can shape pest outbreaks and pesticide use in vineyards,” said co-author Jay Rosenheim, distinguished professor in the UC Davis Department of Entomology and Nematology.

Their results suggest that landscape simplification could affect not only farm yields, but also  environmental and human health. They noted that insecticide applications doubled in vineyard-dominated landscapes but declined in vineyards surrounded by shrubland. “Habitat conservation thus represents an economically and environmentally sound approach for achieving sustainable grape production in Spain,” said Karp.

Why might pests be more of a problem on vineyards surrounded by more vineyards? One possibility is that vast stretches of vineyards allow pest populations to build up quickly. Another possibility is that simple vineyard landscapes may not contain enough resources to support predatory insects that natural control vineyard pests. Whatever the reason, it seems clear that “cultivating crops in monoculture creates the perfect conditions for specialist pest outbreaks,” they related, so “farmers have consistently turned to insecticides to maintain high yields under constant pest pressure.” 

A solution? At an individual level, farmers may better control L. botrana populations through planting native vegetation in and around their farm. Ideally, they would coordinate with each other to maintain and/or restore large patches of productive, shrubland habitats in the surrounding landscape. 

Other co-authors are Rebecca Chaplin-Kramer, Natural Capital Project, Stanford University; and Silvia Winter, Institute of Plant Protection, University of Natural Resources and Life Sciences, Vienna, Austria.

Their work was financed by the research project SECBIVIT, or “scenarios for providing multiple ecosystem services and biodiversity in viticultural landscapes,” and a National Science Foundation/USA grant.