Steve passed away Friday, Nov. 15 at a Sacramento hospital of a heart condition. Born in 1959 in Madison, Wisconsin, he was 60 years old. He was one of the pioneering scientists researching the newly discovered thousand cankers disease (TCD), caused by the walnut twig beetle, Pityophthorus juglandis, in association with the canker-producing fungus, Geosmithia morbida. He was a worldwide authority on the insect, fungus and disease. (See obituary in Davis Enterprise)
In his memory, he was honored with a moment of silence this week at the Entomological Society of America meeting in St. Louis, Mo.
The tributes are pouring in:
Nematologist Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology: "Steve was an excellent chemical ecologist whose research on insect pests of trees proved to be of great importance to landscapes throughout North America.”
Chemical ecologist Walter Leal, UC Davis Department of Molecular and Cellular Biology and past chair of the UC Davis Department of Entomology (now the Department of Entomology and Nematology). "Chemical ecology lost a champion, forestry entomology lost an ally, and we will miss a friend and colleague. Steve served the International Society of Chemical Ecology as Councilor, the Journal of Chemical Ecology as Associate Editor, and mentored many undergraduate and graduate students and postdoctoral scholars. He elucidated biochemical mechanisms related to bark beetle pheromones, leaving behind a legacy of papers and review articles, some of which have already been cited almost one thousand times. I copied from him the style of praising colleagues when citing their good work by adding the advert 'elegantly' like in the following sentence. Steve Seybold elegantly demonstrated how bark beetles make their pheromones."
Doctoral student Jackson Audley of the Seybold lab: "Steve Seybold was a brilliant scientist and an integral component of the forest entomology community, especially here in the western USA. I admired the amount of time he spent out in the field. I have often heard it said that once a field biologist obtains a Ph.D., that they often become something of an 'armchair biologist', not Steve. I have never seen him happier than when he was out on long field excursions, hunting down various trees and tree pests. I hope to emulate that characteristic in my own career. Although my time working with Steve now feels cut abruptly and unfairly short, he imparted a great deal of wisdom upon me in that time. I am incredibly grateful to have had Steve as a mentor and a friend. He contributed a great deal to making me into the scientist I am today. He will be sorely missed."
Seybold lab alumnus Andrew Graves (now a zone leader entomologist with the Forest Service, Forest Health Protection, New Mexico Zone): "We are all shocked and saddened. Steve and I worked together for nearly 20 years. A faithful mentor, constant teacher, an incessant researcher to whom the time of day or length of time were meaningless, a good friend who contributed much to our world. A too early passing and a great loss for us all. He was a good man and will be missed by many. If I had to guess, he would've been disappointed he didn't finish that last manuscript."
Seybold lab alumnus Stacy Hishinuma, who went on to accept a position in the Pacific Southwest Region, San Bernardino: "Steve was a pivotal person in my life. I worked with him for more than 10 years and during that time he pushed me to have the highest scientific standards and taught me all I know about research. He was an involved mentor and cared deeply about the success of his students. His love was expressed through the red marks on our manuscripts, the time he spent helping us with presentations, and the pop quizzes on insect identification. When I started graduate school, people advised me to be the first person in and the last person to leave. This was impossible in the Seybold lab since Steve regularly started working before dawn. It was somehow always startling when I would email Steve at 4:00a, before heading to sleep, and he would immediately respond. Steve's work ethic was unprecedented. It was inspiring to see his passion for research. His love for science was only rivaled by his love for his daughters. I'll always miss the conversations we had driving to field sites, eating at his go-to restaurants, and geeking out about bark beetles. Thank you for everything Steve. I hope I can help carry on your legacy through my own work as a forest entomologist."
We knew him as an incredible scientist with an immense curiosity, an outstanding teacher, and a kind and caring friend. A few of the last news stories we wrote about him:
- A Sign of the Times: Why This Black Walnut Tree Is Dying
- Meet the Extreme Insects at the Bohart Museum of Entomology Open House
- Walnut Twig Beetle and Fungus Has Caused 'Profound Damage to Black Walnut Trees
Steve is survived by his widow, Julie Tillman, and daughters Natalie, 11, and Emily, 17. "Steve loved his work and his daughters with his whole self and heart," Julie said. "He will be sorely missed by his family and friends, his lab family and his huge network of professional colleagues."
A visitation will be held from 5 to 7 p.m. Friday, Nov. 22, at Smith Funeral Home in Davis. A service will be held on Saturday, Nov. 23, at Saint James Church in Davis at 10 a.m. with interment at a later date near his father at Forest Hill Cemetery in Madison. Memorials in his name may be made to the American Heart Association, National Parks Conservation Association or the Entomology and Nematology Student Support fund at UC Davis.
Audley just received the 2019 Western Forest Insect Work Conference (WFIWC) Memorial Scholarship Award for his research on the chemical ecology of an invasive bark beetle, the walnut twig beetle.
Audley, who conducts his research in a commercial orchard near Winters, investigates behavioral chemicals that repel the walnut twig beetle from landing on English walnut trees. The walnut twig beetle (Pityophthorus juglandis), in association with a canker-producing fungus, Geosmithia morbida, causes the insect-pathogen complex known as thousand cankers disease.
“The disease threatens both native black walnuts across North America and agriculturally important English walnut, particularly in California,” said Audley, who received the $1000 award at the recent conference in Anchorage. “My research focuses on improving our understanding of the walnut twig beetle's chemical ecology and developing a semiochemical repellent tool to manage the threat.”
The scholarship memorializes Mark Duane McGregor, a bark beetle management specialist who died in April 1990 while conducting forest entomology research in Idaho. The scholarship has since expanded to honor other deceased WFIWC members.
Audley, on a path to receive his doctorate in entomology by December 2019, is co-advised by Steve Seybold, lecturer and faculty affiliate with the UC Davis Department of Entomology and Nematology and a forest entomologist and chemical ecologist with the Pacific Southwest Research Station, USDA Forest Service, Davis; Associate Professor Louie Yang of the UC Davis Department of Entomology and Nematology, and Professor Richard “Rick” Bostock of the UC Davis Department of Plant Pathology. The Bostock lab is heavily involved with the chemistry side of Audley's repellent research. Seybold and Bostock have shared a California Department of Food and Agriculture grant with the doctoral student.
Audley is invited to deliver a plenary lecture on his dissertation at the WFIWC meeting next year in Calgary, Alberta.
Audley, who was born in Washington D.C., but spent most of his childhood in Atlanta, Ga., was first introduced to forest entomology while he was a student at the University of Georgia, Athens, where he received his bachelor of science in wildlife biology and natural resource recreation and tourism in 2009. He then received his master's degree in forestry in 2015 from the University of Tennessee, Knoxville, where he focused his thesis on managing the walnut twig beetle (WTB) in cut black walnut logs, live edged boards, and nursery stock. He joined the UC Davis doctoral program in September 2015.
His research at UC Davis includes conducting field-based research relating to the chemical ecology of WTB in northern California walnut orchards and native riparian forests; assisting on several WTB-related research projects, including a trial on the efficacy of emamectin benzoate in protecting walnuts from WTB and thousand cankers disease (TCD), and a project assessing the impact of WTB and TCD on the productivity of English walnut orchards in California. In addition, Audley has monitored and sorted the trap catches from numerous walnut twig beetle flight intercept traps, maintained year round in northern California and performs sorting and identification for similar traps maintained by the Tennessee Department of Agriculture.
Active in WFIWC, Audley delivered a presentation on the walnut twig beetle in 2018 as part of an invasive species symposium. He also serves as the student representative on the Founders' Award Committee. At UC Davis, he teaches and mentors students on forest entomology.
His career plans? “I plan to devote my career to conducting chemical ecology-based research of bark and wood boring beetles that threaten trees in forest landscapes in the western U.S.,” Audley said. “In this capacity, I plan to continue adding to the scientific understanding of bark beetle ecology and management.”
Audley aims to engage with the scientific community and public alike in the arena of forest health issues and sound forest management practices. “Our western forests are in dire need of sound forest management to return them to a healthier state, and I plan to conduct and disseminate research to help achieve that goal.”
Well done, well done!
It's about 150 years old, 50 feet in height, and measures about five feet in diameter. And it's dying.
What's killing it is thousand cankers disease (TCD), an emerging insect-fungus complex.
It's killing a lot of black walnut trees.
In fact, TCD has caused profound damage to black walnut trees not only in urban areas of California and other western states, but in Pennsylvania, Tennessee and Virginia, according to a newly published review by UC Davis-affiliated scientists and their colleagues.
The article, “Status and Impact of Walnut Twig Beetle in Urban Forest, Orchard and Native Forest Ecosystems,” published in the Journal of Forestry, updates the spread of the disease, and chronicles the role of the bark beetle, Pityophthorus juglandis, and the canker-producing fungus, Geosmithia morbida, in killing walnut trees, especially black walnuts.
Native to southwestern United States and northern Mexico, the bark beetle, about half the size of a grain of rice, “has invaded urban, orchard and native forest habitats throughout the United States, as well as Italy,” said lead author and forest entomologist Steven Seybold of the Pacific Southwest Research Station, USDA Forest Service, Davis, and a lecturer and researcher with the UC Davis Department of Entomology and Nematology.
Walnut twig beetles (WTB) tunnel into branches and trunks of walnut (Juglans) where they create galleries for mating and reproduction. They carry spores of the fungus into their galleries, and the resulting fungal infection causes formation of cankers, which coalesce and girdle branches and stems.
“The walnut twig beetle is a significant pest of very large trees because it sequentially attacks the small branches--though ironically not the twigs--all the way down the trunk to the soil line,” said Seybold, a pioneering scientist of TCD, who first found TCD evidence in Davis in 2008. “Most bark beetle species are not this thorough in using all of the phloem tissue in their plant hosts. In Davis right now, in the courtyard next to Sophia's Thai Restaurant, 129 E St, the tiny beetle is gradually killing the largest northern California black walnut tree in the city. It has taken nearly a decade, but the crown of the massive tree is nearly completed killed.”
Seybold estimated that the E Street tree is about 150 years old, "maybe older." It measures almost 65 inches or just over five feet.
Seybold noted that the disease is “unique because of its multifaceted negative impact on walnut trees involved in landscaping, food production, and forestry. Walnut trees are valuable ecologically and for food and timber, so the walnut twig beetle is a good model in which to study the impact of a bark beetle on forest and agro-ecosystem services.”
The five co-authors of the synthesis article include Stacy Hishinuma and Andrew Graves, two USDA forest entomologists with UC Davis connections. Hishinuma, who works in the Pacific Southwest Region, San Bernardino, and holds a doctorate in entomology from UC Davis, studied in the Seybold and Mary Lou Flint labs, UC Davis Department of Entomology and Nematology. Graves, who works in the Southwestern Region, Albuquerque, N.M., is a former postdoctoral fellow in the UC Davis Department of Plant Pathology.
Other co-authors are Professor William Klingeman III of the Department of Plant Sciences, University of Tennessee, and forest entomologist Tom Coleman with the USDA Forest Service's Southern Region, Asheville, N.C..
UC Davis doctoral student Jackson Audley of the Seybold lab and Richard Bostock lab (Plant Pathology), contributed photos of dead and dying walnut trees in the Davis area, along with UC Davis doctoral student Corwin Parker and Hishinuma. Audley, who is researching an ensemble of behavioral chemicals that repel the walnut twig beetle from landing on English walnut trees, conducts his research in a commercial orchard near Winters.
“WTB is one of a few invasive bark beetles in North America where expanding distribution and impact have been pronounced enough to affect other species, communities, and ecosystems to the extent that services provided by urban forests, agroecosystems, and wildland areas have been altered,” the co-authors concluded in their paper. “We envision that ecological impacts of WTB will continue to unfold across a wider geographic area to affect various types of key services, i.e., provisioning (e.g., timber and nontimber products); regulating (e.g., air and water quality/quantity, climate regulation); and cultural (e.g., recreation, aesthetics, shade) services.”
Scientists first collected the beetle in North America in 1896 in New Mexico, 1907 in Arizona, 1959 in California, and 1960 in Mexico, but never considered it a major pest of walnut trees until black walnuts began deteriorating and dying in New Mexico in the early 2000s. Walnut tree mortality that occurred in the early 1990s in the Wasatch Mountains of Utah and in the Willamette Valley of Oregon is now attributed to TCD.
“Currently, good cultural practices and sanitation of infested materials are the primary strategies for disease management within orchards and also for prevention of spread of the disease and vector to regions with low rates of infection,” according to the UC Statewide Integrated Pest Management Program (UC IPM)>
UC IPM recommends that trees with less than 50 percent live crown be removed to reduce the buildup of walnut twig beetles and inoculum in the trunk and larger scaffold branches. "Chemical control with either fungicides or insecticides is not recommended for management of thousand cankers disease," UC IPM says.
Which brings us back to the massive black walnut tree that is dying on E Street in Davis. If it dates back to 1868, that's the year the city of Davis was founded. Its namesake, Jerome C. Davis, owned a stock farm on the site.
Who was in the White House and who was in the California governor's mansion that year? Andrew Johnson and Henry Haight, respectively. That was also the year that trustees founded the University of California in Oakland; Clark Kerr became the first president. And 1868 was the year Memorial Day was first observed in the United States...and when author Louisa May Alcott published the first volume of her coming-of-age novel, Little Women.
The little tree in Davis became of age, too, growing into a giant tree offering shade, shelter and sustenance. Who would have thought that a tiny insect, half the size of a grain of rice, would play a major role in its demise?
Have you ever seen an ambrosia beetle, a red turpentine beetle, an ice cricket, a brine fly or a sand wasp?
You will if you attend the UC Davis Bohart Museum of Entomology open house on “Extreme Insects: Fire and Ice,” on Sunday afternoon, Aug. 19.
The public event, to take place from 1 to 4 p.m. in Room 1124 of the Academic Surge Building, Crocker Lane, is free and family friendly. It will emphasize "fire and insects."
“There are a number of species that are specifically attracted by smoke to damaged trees,” said Lynn Kimsey, director of the Bohart Museum and professor of entomology at UC Davis. “Wildland fire fighters hate them because some of the beetles fly at them, crawling into their turnouts and biting them. Fire insects include jewel beetles, some horntail wasps and a few others."
In addition to fire insects, Kimsey said that the Bohart open house will cover other insects adapted to extremes:
- Ice: ice crickets and ice flies, both native to California
- Extreme acid: midges that live only in highly acidic mine run-off
- Hot water: midges found in hot springs just below the boiling point
- Salt: the brine flies of Mono Lake.
- Desert: sand wasps
Regarding the beetles that attack the firefighters, these are “The flatheaded borers (Buprestidae) and they will actually nip the firefighters as they land,” said chemical ecologist Steve Seybold with the USDA Forest Service, Pacific Southwest Research Station, Davis, and a lecturer/researcher with the UC Davis Department of Entomology and Nematology.
Insects that like ethanol/burned phloem include the red turpentine beetle, the ambrosia beetles, the "sour cambium" beetles, and some of the larger woodborers, Seybold said. “These are the 'undertakers' of the trees, if you will. Certain bark and ambrosia beetles specialize in colonizing burned tissue that gives off ethanol as a sign of fermentation. These insects wait until things have cooled off a bit before they bore into the trees."
"Often when you visit a burned area," Seybold said, "you'll see piles of white dust coming out of the trees that have blackened bark. This dust is made by ambrosia beetles--and other larger woodborers--that can make use of the carbon that is still present in these moribund trees. Ambrosia beetles 'consume' this carbon indirectly by farming fungi in their galleries. The fungus serves as a conduit for the nutrients in the wood. Some of the larger woodboring insects have other adaptations like specialized enzymes that degrade cellulose or hemicellulose."
Seybold called attention to an article titled “Attraction of Melanophila Beetles by Fire and Smoke,” authored by noted beetle expert E. Gorton Linsley (1910-2000) and published in April of 1943 in Scientific Notes, the Journal of Economic Entomology. Linsley, who received his doctorate from UC Berkeley in 1938, wrote that thousands of cigarette smokers at the UC Berkeley football games were complaining of beetles swarming into the stadium and biting their hands and necks.
The smoke on "still days sometimes hangs like a haze over the stadium during a big game," wrote Linsley, identifying the beetles as Melanophilaconsputa Lec. and M. acuminata (family Buprestidae). M. consputa is commonly called “the charcoal beetle.”
Linsley also reported receiving "complaints from sawmill operators, fire fighters and smelter plant workers regarding annoyance by buprestid beetles of the genus Melanophila. These beetles appear to be greatly stimulated by heat and attracted by smoke. They normally breed in fire-scarred pines and under ordinary conditions, they are rarely encountered in nature. However, on hot days during the dry season, especially in late summer and fall, they sometimes fly in unbelievable numbers to forest fires, burning refuse dumps, refineries, smelter plants, etc.”
Wildfires continue to rage in California. As of Aug. 13, the 5,255 California wildfires this year have burned 958,812 acres, according to the California Department of Forestry and Fire Protection and the National Interagency Fire Center. To date, the still-active Mendocine Complex fire, the largest wildfire in California history, has charred more than 344,000 acres.
The Bohart Museum open house also will include a family craft activity involving extreme insects. The museum houses a global collection of nearly eight million specimens and is the home of the seventh largest insect collection in North America, and the California Insect Survey, a storehouse of the insect biodiversity. It also houses a live "petting zoo" of Madagasar hissing cockroaches, walking sticks, tarantulas and praying mantids, and a year-around gift shop, stocked with T-shirts, sweatshirts, books, jewelry, posters, insect-collecting equipment and insect-themed candy.
The Bohart Museum's regular hours are from 9 a.m. to noon and 1 to 5 p.m. Mondays through Thursdays. It is closed to the public on Fridays, Saturdays and Sundays and on major holidays. Admission is free. More information on the Bohart Museum is available on the website or by contacting (530) 752-0493 or emailing email@example.com.
Not UC Davis animal biology major Crystal Homicz, treasurer of the UC Davis Entomology Club.
"Cupcake" is the name of her six-month-old praying mantis that she exhibited at the Bohart Museum of Entomology last Saturday during the seventh annual Biodiversity Museum Day.
The adult mantis is a Rhombodera megaera, native to southern China and Thailand, Homicz told the crowd.
The species is one of the largest mantises in the world; it can reach 4 to 5 inches in length. However, Cupcake is not that large.
Homicz, a student researcher in Steve Seybold's forest entomology lab, also has the male of this species and hopes to mate it this week. "I've been feeding her lots of flies so I hope the male doesn't lose his head," she said, referring to sexual cannibalism that can occur.
A females can lay about three oothecae (egg cases) in her lifetime. Between 150 to 250 nymphs can hatch from an "ooth."
The Biodiversity Museum Day, featuring 13 collections or museums on campus, drew thousands of visitors exploring the diversity of life, said chair Tabatha Yang, education and outreach coordinator for the Bohart Museum of Entomology. Seven were open from 9 a.m. to 1 p.m.: Museum of Wildlife and Fish Biology; Bohart Museum of Entomology, Raptor Center, Paleontology Collection, Arboretum and Public Garden; Phaff Yeast Culture Collection; and the Viticulture and Enology Culture Collection. Six were from noon to 4 p.m.: Nematode Collection, Botanical Conservatory, Center for Plant Diversity Herbarium, Anthropology Museum, Häagen-Dazs Honey Bee Haven and the Design Museum.
Plans are already underway for the eighth annual Biodiversity Museum Day. The next major campus event is the 104th annual UC Davis Picnic Day, set April 21.