- Author: Kathy Keatley Garvey
But agriculturists and scientists have.
The spotted-wing drosophila (SWD), Drosophila suzukii, is an agricultural pest that is super tiny.
It's approximately 2 to 4 millimeters in length with a wingspan of 5 to 6.5 millimeters. One millimeter is approximately 0.039 inches. There are 25.4 millimeters in 1 inch. So, the adult is about the size of a grain of sand, which can measure 0.5 to 2 mm in diameter.
SWD, native to southeast Asia and first discovered in California in 2008, lays its eggs in such soft-skinned, ripening fruits as strawberries, raspberries, cherries, blueberries, peaches, nectarines, apricot and grape.
In 2008, the first year of its discovery in California, the economic loss attributed to this pest amounted to $500 million. Latest statistics from 2015 indicate a $700 million national economic loss.
Lead author of the paper, “Transcriptome Analysis of Drosophila suzukii Reveals Molecular Mechanisms Conferring Pyrethroid and Spinosad Resistance,” is Christine Tabuloc, then a doctoral candidate and now a postdoctoral researcher working under the mentorship of Professors Chiu and Zalom.
"In this work, we leveraged high throughput sequencing to identify biomarkers of insecticide resistance in D. suzukii,” Tabuloc explained. “We found that different genes are responsible for resistance to different chemicals. Specifically, we found that genes involved in metabolism are highly expressed in flies resistant to pyrethroid insecticides. We also observed evidence of two different mechanisms of resistance in 2 lines generated from a single spinosad-resistant population. We found an increased expression of metabolic genes in one line and increased expression of cuticular genes in the other.”
Tabuloc added that “our work has enabled for the detection of resistance in California populations, and we are currently doing a nationwide screening to determine whether resistance is now present in other states. Currently, we are working with the Zalom lab to use the results of our assays to try and combat resistance. There are experiments in progress trying to increase the efficacy of insecticides by blocking some of the genes involved in resistance, such that the enzymes encoded by those genes have decreased function."
A giant in the entomological world, Zalom directed the UC Statewide Integrated Pest Management Program for 16 years. He is an Honorary Member of the Entomological Society of America (ESA), the highest ESA honor, and he served as its president in 2014.
“This work not only represents good science; it has very practical implications," Zalom said. He and Tabuloc presented results of the work at a special berry grower seminar on insecticide resistance organized by UC Agriculture and Natural Resources (UC ANR) Farm Advisor Mark Bolda, strawberry and caneberry farm advisor in Santa Cruz, Monterey and San Benito counties, Mark Bolda in Watsonville.
"The presentations were extremely well-received," Zalom noted. "The original program was targeted for about 1.5 hours, but the meeting extended to over three hours due to the extent of questions and great discussion that followed. Growers and their consultants are hungry for new information that they find interesting and potentially useful, and this work was clearly of interest to them.”
Said Bolda: “The research was top shelf and the need, of course, is very great. Some of the information that Frank and Christine presented has been put into immediate use in the industry.”
What most people don't know is that Bolda was the first to discover the pest in North America. That was in 2008.
"He asked me to come down to look at it and the problem...we weren't able to get an actual species identification until 2009!" Zalom said.
As the pest continues to spread throughout much of the country, anxious growers are worried about its increased resistance to pesticides. The UC Davis research team is alleviating that worry.
- Author: Kathy Keatley Garvey
The project? Fourteen articles in The Journal of Economic Entomology's Special Collection: Research Advances in Spotted-Wing Drosophila suzukii Management, published in the August 2022 edition.
The insect? It's native to Asia and primarily targets soft-skinned fruits in the berry industry, such as raspberries, blackberries, blueberries, strawberries, and cherries. The tiny insect, about 1/12 to 1/8 inch long, invaded the continental United States in 2008.
The authors? They're from eight countries: United States, Austria, Brazil, Canada, Italy, Spain, Sweden, and the United Kingdom and represent perspectives from universities, federal and state laboratories, growers, and pest product companies.
Thirteen UC Davis scientists or former affiliates are among the authors who contributed.
“All of the papers were by invitation of the co-editors of the special collection—Jana Lee, Cesar Rodrigue-Saona, and me,” said journal editor-in-chief Frank Zalom, a UC Davis distinguished professor emeritus and recall professor in the Department of Entomology and Nematology. Zalom's research includes the insect, Drosophila suzukii.
Lee, formerly with the UC Davis laboratory of the late chemical ecologist Steve Seybold, is a research entomologist with the Horticultural Crops Research Unit, U. S. Department of Agriculture, Agricultural Research Service, Corvallis. Rodriguez-Saona, who received his doctorate from UC Riverside, is an Extension entomologist with the Department of Entomology, Rutgers University, the State University of New Jersey.
One paper, Spatio-temporal Variation of Spinosad Susceptibility in Drosophila suzukii (Diptera: Drosophilidae), a Three-year Study in California's Monterey Bay Region, is from the Zalom lab and includes co-author, molecular geneticist and physiologist Joanna Chiu, professor and vice chair of the Department of Entomology and Nematology.
Since 2008, "D. suzukii has become a key economical pest of raspberries, blackberries, blueberries, strawberries, and cherries in the United States and worldwide," the editors wrote in their introductory remarks. "Not surprisingly, the number of publications has proliferated from 29 publications as of 2010 to 978 additional publications between 2011 and 2021 from a Web of Science search for ‘Drosophila suzukii.' While many publications are available, this special collection will highlight advances in D. suzukii pest management since its U.S. invasion. We solicited papers by open call and received 66 abstracts, and selected 14 papers covering: 1) review, 2) monitoring and risk, 3) behavioral control, 4) biological control, 5) cultural control, and 6) chemical control."
The editors pointed out that “Given that 14 years of research has accumulated since the continental U.S. invasion, it was fitting to include two reviews that provide a different scope than was covered in prior reviews on D. suzukii biological control (Lee et al. 2019, Wang et al. 2020), trapping (Burrack et al. 2020), cultural control (Schöneberg et al. 2021), and chemical ecology (Cloonan et al. 2018). This special collection is anchored by Tait et al. (2021), a review of the most promising methods as part of an Integrated Pest Management (IPM) strategy against D. suzukii across the world since 2008. The effectiveness, impact, sustainability, and present stage of development and implementation are discussed for each of the considered techniques, and insights for continued development are presented.”
The researchers related that the pest is a significant threat to California's berry production industry, which the California Department of Food and Agriculture (CDFA) valued at more than $2.8 billion in 2019. Caneberries, in particular, "are a preferred host of D. suzukii, and California accounts for 89.4 percent of all production in the United States, with the Monterey Bay region producing about half of the state's raspberries and blackberries (CDFA 2020). This pest has now spread to all major berry and cherry growing areas of the United States."
The collection is meant to serve "as a key reference point for entomologists across many institutions (e.g., academia, government, and industry) on important advances in D. suzukii pest management," according to the Entomological Society of America. "The articles in this collection will also provide scientists information on potential research gaps that will help guide future research directions on this important pest. The goal is to preserve and catalog articles on various aspects of D. suzukii pest management, i.e., monitoring, cultural control, chemical control, behavioral control, and biological control, that will be shared among entomologists."
- Author: Kathy Keatley Garvey
"The spotted-wing drosophila, Drosophila suzukii, first invaded California in 2008," says UC Davis postdoctoral researcher Brian Gress, "and has since rapidly spread throughout North America and Europe."
Gress will discuss "Host Selection and Resistance Evolution in Drosophila Suzukii" at a UC Davis Department of Entomology and Nematology seminar at 4:10 p.m., Wednesday, Jan. 9 in 122 Briggs Hall.
He will be introduced by his advisor, integrated pest management specialist Frank Zalom, distinguished professor of entomology, UC Davis Department of Entomology and Nematology, and a past president of the Entomological Society of America.
"The female D. suzukii possess a unique serrated ovipositor that allows them to cut into ripening fruit, causing major economic losses for berry and cherry producers across the globe," Gress writes in his abstract. "Growers rely heavily on the use of insecticides to control this pest, and spinosad is among the most important materials currently available for protecting susceptible host crops."
Recent reports, however, "have raised concerns that the efficacy of this insecticide is declining in fields near Watsonville, Calif., a major hub of commercial berry production in the United States," Gress says. "In this seminar, I will present a series of studies aimed at assessing the degree of resistance in the population, the evolutionary potential for resistance to increase, and novel strategies for managing resistance in the field."
The spotted-wing drosophila, a major agricultural pest, damages fruit in many California counties, according to the UC Statewide Integrated Pest Program (UC IPM). "The males have a black spot toward the top of each wing. The females have not spots. They have "a very prominent, sawlike ovipositor for laying eggs in fruit."
Gress joined the Zalom lab in January 2017. He lists his research aims as
- understand the evolutionary processes and genetic mechanisms that give rise to insecticide resistance in agricultural pests;
- develop sustainable and cost-effective strategies for managing agricultural pests by disrupting insect mating behavior and reproductive physiology; and
- assess population dynamics and demography of wild insect populations in the field.
Gress holds bachelor of science degrees in biology and psychology, magna cum laude, from Iowa State University, Ames (2011), and a doctorate in biological science from Syracuse (N.Y.) University (2016).
At Syracuse, Gress received the 2016 Alexander Gourevitch Memorial Award, in recognition of research excellence; and the 2016 College of Arts and Sciences Outstanding Dissertation Award. In 2015 he was awarded a National Science Foundation Doctoral Dissertation Improvement Grant of $19,050.