They're small, about 1 mm long or less, with characteristic fringed wings. They fly, but not well.

But thrips do pack a powerful punch. 

A major pest of many agricultural crops, including lettuce, they damage plants by (1) sucking their juices and (2) transmitting viruses.  

If you've been following the thrips damage in the lettuce production in the Salinas Valley, or want to know more about thrips, the UC Davis Department of Entomology and Nematology's virtual seminar on Wednesday, Jan. 20 should interest you.

Research entomologist Daniel Hasegawa of the Crop Improvement and Protection Research Unit, Agricultural Research Service, U. S. Department of Agriculture, will speak on "Landscape and Molecular Approaches for Managing Thrips and Thrips-Transmitted Viruses in the Salinas Valley" at the department's first seminar of the winter quarter.  

The hour-long virtual seminar, via Zoom, begins at 4:10 p.m., announced agricultural Extension specialist Ian Grettenberger, seminar coordinator. To access the seminar, fill out this Google form link at https://bit.ly/3oWYjnt. (Contact Grettenberger at imgrettenberger@ucdavis.edu.)

"In 2019-2020, lettuce production in the Salinas Valley of California was devastated by thrips-transmitted impatiens necrotic spot virus (INSV)," Hasegawa says in his abstract. "Due to the inherent challenges in managing thrips using conventional chemical tactics, and no direct means for managing the virus, there is a strong need for new management strategies."

This seminar, he says, will provide an overview of 

1. The challenges in managing thrips and INSV in lettuce production
2. What we've learned about the epidemiology of thrips and INSV, and
3. Opportunities to improve cultural practices and develop biotechnology tools, such as RNAi for managing thrips and INSV in the Salinas Valley.

Hasegawa joined the Salinas USDA-ARS team in May 2019 after serving as a postdoctoral research associate (molecular biology) for three years with the USDA-ARS in Charleston, S. C.  He specializes in vector entomology, molecular biology and biotechnlogy. "My lab uses a variety of techniques to understand insect vector-virus relationships that impact plant health and agriculture," he says on Linked In. "We use molecular, genetic, and epidemiological concepts to understand drivers of vector-borne transmission of pathogens and utilize genetic technologies (e.g. RNAi and CRISPR), to improve agriculture productivity and sustainability."

Hasegawa received his bachelor of science degree in biochemistry in 2007 from UC Riverside and his doctorate in biology from Clemson University in 2013. 

The mission of the Crop Improvement and Protection Research Unit is to improve germplasm of lettuce, spinach and melon, determine basic biology of viral, fungal and bacterial diseases affecting these crops, develop alternatives to methyl bromide as a soil fumigant for control of soilborne pests in strawberry and vegetables, reduce postharvest losses of lettuce, develop scientifically based organic crop production practices, and develop methods for control of weeds. (See more on the Pacific West Area website.)

"More than 90 percent of the lettuce sold in the United States is grown in California, and the majority of production from April through October occurs in the Salinas Valley, while production form November through March occurs in California's Imperial Valley," according to keepcaliforniafarming.org.

The UC Statewide Integrated Pest Management Program (UC IPM) says this about thrips: "Thrips, order Thysanoptera, are tiny, slender insects with fringed wings. They feed by puncturing the epidermal (outer) layer of host tissue and sucking out the cell contents, which results in stippling, discolored flecking, or silvering of the leaf surface. Thrips feeding is usually accompanied by black varnishlike flecks of frass (excrement). Pest species are plant feeders that discolor and scar leaf, flower, and fruit surfaces, and distort plant parts or vector plant pathogens. Many species of thrips feed on fungal spores and pollen and are often innocuous. However, pollen feeding on plants such as orchids and African violets can leave unsightly pollen deposits and may reduce flower longevity. Certain thrips are beneficial predators that feed on other insects and mites."

"Thrips can readily move long distances floating with the wind or transported on infested plants, and exotic species are periodically introduced," UC IPM notes. 

Congratulations to the international team of scientists, including UC Davis entomologist and co-author Diane Ullman, on their publication involving 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. 

(See more information on the project on the UC Davis Department of Entomology and Nematology website)

Thrips expert Cheryle O'Donnell, a true UC Davis success story, is now settled into her new position.

As of April 6, the former San Diego resident is the National Thysanoptera Taxonomist with the National Identification Services (NIS) at the Systematic Entomology Laboratory (SEL) in Beltsville, MD.

Specifically, her position is with the National Identification Services (NIS) of the Plant Protection and Quarantine (PPQ) program of USDA's Animal and Plant Health Inspection Service (APHIS) or what USDA officials refer to as "APHIS PPQ NIS." The Thysanoptera collection of the Systematic Entomology Laboratory (SEL) is housed with USDA's Agricultural Research Service (ARS). 

“I love my work,” she said, “and I love my favorite insect, thrips.”

Thrips are tiny insects that cause billions worth of damage annually to U.S. agricultural crops. Barely visible to the naked eye, they heavily damage fruits, vegetable and horticultural crops, so much so that they can—and do--pose a biosecurity threat. In 1996, Cuba's Fidel Castro accused the United States of aerially releasing Thrips palmi over potato fields.

“Of the more than 5000 species of thrips known in the world, some are serious pests, and some are beneficial as pollinators and predators,” O'Donnell said. “Some thrips transmit plant diseases, such as the tomato spotted wilt virus and the Impatients necrotic spot viruses.”

“To monitor agricultural crops effectively, it's important to be able to identify them, but it's difficult to do so without understanding thrips taxonomy and identification,” O'Donnell said. “Thrips are so small—one millimeter long or less--that they're like a speck. Inspectors see larvae, eggs and adults on plant material coming in. It's difficult to separate species at the life stage of eggs, larvae and adult males.”

O'Donnell arrived at UC Davis in the mid-1990s as a single mom raising a young daughter. A former employee of an electronic manufacturing business, she enrolled at UC Davis to study ornamental horticulture. At the same time she managed a landscaping business.

“There were many times I was doubtful that I could continue to meet the demands of my chosen field,” O'Donnell said, crediting her family, friends and UC Davis scientists with offering her the support she needed to complete her education.

 O'Donnell holds three degrees from UC Davis: a bachelor's in agricultural systems and the environment (1997),  a master's degree in plant protection and pest management (2000) and a doctorate in entomology (2007).

After receiving her doctorate, she joined the USDA as “the co-lateral Thysanoptera specialist, USDA-APHIS-PPQ,” west of the Mississippi. That is, she was a key thrips specialist for the Animal and Plant Health Inspection Service's Plant Protection and Quarantine Program. Her work involved detecting, identifying and intercepting thrips and other pests arriving at U.S. ports from around the world.

Her major professor Diane Ullman, a professor in the UC Davis Department of Entomology and Nematology, describes her as "a tremendously talented biologist and she holds a real fascination for thrips, their classification, host relationships and biology."

"She will do a fantastic job in this position, which will be important to the global community studying thrips and trying to develop management strategies," Ullman told us.

Read more about Cheryle O'Donnell here. She offers good advice to prospective graduate students in encouraging them to follow their dreams: "Focus on your goals, never deviate from those goals, and never allow obstacles to get in the way,” she advises. "It is a difficult and challenging path you have chosen but it will be worth all the hard work. The UC Davis community, the ‘village' which supports you, is an experience you will never forget and the payoff will be great throughout your life.”

Meanwhile, O'Donnell is anticipating two mid-May thrips conferences at the Asilomar Conference Center, Pacific Grove. One of the key organizers is Professor Ullman.  See more information.

If you grow tomatoes, you ought to be concerned about thrips.

They're pests of  fruits, vegetable and horticultural crops, including tomatoes, grapes, strawberries and soybeans. They're barely visible to the naked eye, but oh, how disastrous they can be. Some thrips transmit plant diseases, such as the tomato spotted wilt virus.

Enter Professors George Kennedy and Diane Ullman.

Kennedy, the William Neal Reynolds Distinguished Professor of Agriculture at North Carolina State University. Raleigh, N.C., will speak on "Modeling the Epidemiology of Tomato Spotted Wilt: Understanding the Role of Thrips Population Dynamics and Virus Inoculum Sources" from 12:10 to 1 p.m., Wednesday, April 1 in 122 Briggs Hall, as part of the UC Davis Department of Entomology and Nematology's winter seminar series. 

Colleague/collaborator DianeUllman will introduce him.

"Thrips-transmitted, tomato spotted wilt virus (TSWV), which has an extremely broad host range and is transmitted exclusively by thrips, ranks among the most economically important plant viruses affecting crops worldwide," Kennedy says in his abstract.

"Effective management of this virus in commercial crop production systems requires an understanding of the factors that determine the timing and magnitude of virus spread. This seminar will discuss the ways in which seasonal weather events influence the dispersal dynamics of vector thrips populations, the abundance of virus inoculum sources in the landscape, and ultimately the timing and magnitude of TSWV spread into susceptible crops. It will further provide an illustration of how efforts to model these relationships improved understanding of the epidemiology of TSWV and led to the development of a TSWV risk prediction tool that is now being used in pest management decision making."

Kennedy, past president of the Entomological Society of America (ESA), holds a bachelor's degree in entomology from Oregon State University and a doctorate in entomology from Cornell University.  See his biosketch on the ESA website.

Ullman and Kennedy are among those organizing two consecutive mid-May conferences at the Asilomar Conference Center, Pacific Grove. International scientists, Extension specialists, and agricultural industry professionals will target  thrips and insect-vectored pathogens.

 The first conference, to take place May 14-16, is “Enhancing Risk Index-Driven Decision Tools for Managing Insect-Transmitted Plant Pathogens,” sponsored by the USDA's National Institute of Food and Agriculture's Agriculture and Food Research Initiative (USDA NIFA/AFRI). Ullman is co-principal investigator of the five-year, $3.75 million grant awarded in 2012 from the USDA AFRI/NIFA to develop and implement a national scientific and educational network to limit thrips-caused crop losses. This conference will convene experts in modelling, risk assessment, and innovative IPM technology in an intimate setting to discuss the latest breakthroughs in modelling insect vectored plant pathogen threats and mobile applications for risk assessment and management strategy assessment.

The second conference is the Xth International Symposium on Thysanoptera and Tospoviruses, to be held May 16-20.  "This meeting is the tenth in a series of international symposia that, over 30 years, have grown to be the dominant vehicle and venue for information exchange between scientists investigating problems related to thrips and tospoviruses around the world," Ullman said. "These symposia have been instrumental in extending knowledge and producing new solutions and innovations in thrips and tospovirus management worldwide, by providing a forum for sharing research findings and integrating fundamental and applied knowledge.

And about those thrips...

The tiny insects pierce hundreds of species of plants, sucking the nutrients and causing   billions of dollars in damage to U.S. agricultural crops. As mentioned, they transmit plant viruses in the genus Tospovirus, such as the tomato spotted wilt virus. Read more on the UC IPM website.

“There are 23 additional approved and emerging tospovirus genotypes transmitted by at least 14 thrips species (Thysanoptera: Thripidae),” said Ullman, who has been researching thrips and tospoviruses since 1987.

That's something to think about when you're planting your tomatoes this spring...