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.
Between 2005 and 2016, the disease killed nearly 60 percent of the 210 specimens of southern California black walnut mature trees in the USDA Agricultural Research Service's National Clonal Germplasm Repository Juglans Collection near Winters, Seybold said. “This is only an estimate and the true proportion of the mortality is likely much higher, as only six of the 210 trees were rated as having healthy crowns in August 2016."
Seybold estimated that the E Street tree is about 150 years old, "maybe older." It measures almost 65 inches or just over five feet.
“The walnut twig beetle is also significant because it is the consummate invasive species; it is small enough to travel under the bark of modest-sized pieces of barked wood and it can withstand relatively dry conditions that it might encounter during transit,” Seybold said. “We believe that it has moved from isolated Arizona black walnut trees along creeks and rivers in the desert Southwest to nearly the entire western USA wherever walnut trees of any species have been planted or grew naturally. It has also been transported to Europe and established significant populations in Italy.”
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.”
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, who is researching an ensemble of behavioral chemicals that repel the walnut twig beetle from landing on English walnut trees, contributed photos of dead and dying walnut trees in the Davis area. Audley conducts his research in a commercial orchard near Winters. UC Davis doctoral student Corwin Parker and Hishinuma also provided images of deteriorating walnut trees.
“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.
But have you ever heard of a song featuring the three-cornered alfalfa hopper, Spissistilus festinus, and another one spotlighting the male insect organ, the aedeagus?
And composed by a graduate student at the University of California, Davis, and performed by seven insect-attired UC Davis doctoral students?
That's what happened during the recent UC Davis Picnic Day celebration when the septet gathered in front of Briggs Hall to perform three songs composed by talented musician and entomologist Michael Bollinger, enrolled in the master's degree program, UC Davis Department of Entomology and Nematology. The group performed Bollinger's compositions, “E Major Homeboy (Spissistilus festinus),” “Tragedy (of the Clocks)," and "Jackson's Song (Aedeagal Bits)," as well as a cover song, “Island in the Sun” by Weezer.
The performance went well. Very well. So did Picnic Day.
“My goal was to make sure Picnic Day worked overall, and that, for the band, the sounds were balanced and each of the elements could be heard,” said emcee and band member Brendon Boudinot, president of the UC Davis Entomology Graduate Student Association (EGSA) and a doctoral candidate specializing in ant evolution and classification.
The “Entomology at UC Davis” exhibit at Briggs Hall, the work of the UC Davis Department of Entomology and Nematology, won the campuswide “At One With Nature” category. And the band? It drew loud applause and high praise from the standing crowd.
Their name: “The Entomology Band.” (No take-offs of the iconic “Beatles,” “Buddy Holly and the Crickets” or “Adam and the Ants.”)
Bollinger's original songs capped a day of insect-related activities that included maggot art, cockroach races, nematode identification, scavenger hunts, and honey tasting.
- Molecular geneticist and drummer Yao “Fruit Fly” Cai of the Joanna Chiu lab, dressed in a fruit fly costume, Drosophila melanogaster, which he described as “our favorite model organism in Insecta!”
- Bark beetle specialist and rhythm guitarist Jackson “Darth Beetle” Audley of the Steve Seybold lab, portrayed an Asian longhorned beetle, Anoplophora glabripennis
- Honey bee researcher and bass guitarist Wei “Silverfish” Lin of the Brian Johnson lab, wore a costume that celebrated his moniker, Lepisma saccharina, a small, wingless insect in the order Zygentoma
- Ant specialist and keyboard artist Zachary “Leptanilla” Griebenow of the Phil Ward lab, dressed as “a generic male leptanilline ant (Formicidae: Leptanillinae).” He said: “The yellow color “is not anywhere near so vivid in real life.”
- Systematist and tenor saxophonist Jill “Jillus Saximus” Oberski of the Phil Ward lab, dressed as a “generalized heteropteran,” which she described as “most likely a member of the family Acanthosomatidae (shield bug) or Pentatomidae (stink bug). My family and friends have called me Jillybug, so I came to be the band's representative of Hemiptera.”
- Molecular geneticist and vocalist Christine “The Clock” Tabuloc of the Joanna Chiu lab, wrapped herself in butterfly wings
- Ant specialist and bass guitarist Brendon “Hype Man-tis” Boudinot of the Phil Ward lab, dressed in a green helmet, a blue and gold EGSA bee shirt and a UC Davis cow costume to showcase his department and campus-wide love of bovines.
The seven band members share a love of music.
Drummer Yao Cai, who grew up in Southeast China and holds an undergraduate degree in plant protection and a master's degree from China Agricultural University, has been playing drums since age 17. “We formed as a short-lived band for a show. After that, I realized that I really wanted to keep playing and improved my drum techniques. Thus, we started another band in college and played for six years in college, as an undergrad and graduate student.
“It is very interesting that I was in a band that was the first band in Department of Entomology in China Agricultural University and now we started the first band in Department of Entomology at UC Davis.”
Rhythm guitarist Jackson Audley said he “started learning to play the guitar when I was about 11-12 ish. The first band I joined was a Blink-182 cover band, in which I played the bass guitar, and we played together for most of eighth grade. Then in early high school I joined a Smashing Pumpkins/Radiohead cover band as the second guitarist. Shortly after joining that band, we started making predominantly original music. By the end of high school, we had played a few small shows around the Atlanta area and had recorded a few songs. Unfortunately, the band did not survive the transition into university and we broke up.”
Since then he's mostly played “for fun and I like to jam with folks.”
Jill Oberski, a native of Twin Cities, grew up mostly in Chaska, Minn., “a sleepy suburb of Minnesota.” She received her bachelor's degree in Macalester College in Saint Paul, Minn., where she double-majored in biology and German studies.
“I started playing the piano in kindergarten, and switched to saxophone in fifth grade,” Oberski related. “I played classical and jazz in my school bands from sixth grade through college, and pit orchestra / pep band / marching band in high school as well. I've always been better at classical than rock/jazz/Latin.”
“I probably reached my highest point in late high school, when I served as co-section leader for the saxes in the Minnesota all-state symphonic band--we even got to play a concert in Minneapolis' orchestra hall. These days I'm only involved in the entomology band and some very casual ukulele playing.”
Brendon Boudinot, who received his bachelor's degree in entomology at the Evergreen State College, Olympia, Wash., performed on a metallic sky-blue bass. “I just love art,” he said. “Music is a family thing for me in a number of different ways. Although I have played instruments alone or in groups for many years, nothing really clicked in me until I heard Michael and Yao play together. They shred.”
“The Entomology Band is special to me, and I am just glad I could be a part of it.”
Vocalist Christine Anne Tabuloc, who grew up in the Los Angeles area and received her bachelor's degree from UC Davis in biochemistry and molecular biology, says she does not play an instrument. “I'm far less talented than everyone else in the group,” she quipped. “I've been singing for as long as I can remember. I've been writing lyrics since elementary school. However, I never got around to getting music written for them. I was in choir before and have had solos but that's pretty much it.”
Bass guitarist Wei Lin, who grew up in Xiamen, "a beautiful island in southern China," received his bachelor's and master's degree in China Agricultural University, majoring in plant protection and entomology. “This was my first experience in a band. I just started to learn bass last year when this band was built.”
Following the four-set gig, Boudinot told the appreciative crowd, “That's all we know!”
Pending performances? “The band,” he said, “is on hiatus.”
The seminar takes place from 4 to 5 p.m. in Room 3001 of the Plant and Environmental Science Building.
Audley is presenting a preview of his thesis project in the UC Davis Forest Biology Research Center Seminar Series.
The remaining schedule includes:
Nov. 1 – Alison Scott, postdoctoral student, UC Davis Department of Plant Sciences, “The Polyploid Origin and Evolutionary History of California Redwoods”
Nov. 15 – Brian Smithers, Ph.D student, Ecology Graduate Group, "Mechanisms of Range Shifts in Great Basin Sub‐Alpine Bristlecone Pine Forests."
Nov. 29 – Sarah Bisbing, assistant professor, Forest Ecosystem Science, Department of Natural Resources and Environmental Science, University of Nevada, Reno, "Looking Backward to See Forward: Causes and Consequences of Altered Disturbance and Climate on Western Conifer Forests.”
Dec. 6 ‐ Ryan Tompkins, Forest Silviculturist, U.S. Forest Service/Plumas National Forest, “Sierra Nevada Silviculture in the New World Order: Challenges, Uncertainties, and Opportunities”
All seminars will be held at 4 p.m. in Room 3001 of the Plant and Environmental Science Building. For more information, contact David Neale at email@example.com.
Faculty and graduate students with the UC Davis Department of Entomology and Nematology--and others associated with an ENT/NEM lab--got together for a retreat, held Friday, Oct. 14 through Sunday, Oct. 16 at Sagehen Creek Field Station in Truckee.
Doctoral candidate (and photographer) Sandy Olkowski shared some of her photos of the activities, including insect collecting and dinner preparation. She also took a photo of deer at the campsite.
The participants got to know one another and also enjoyed the natural areas around the field station.
Sagehen Creek Field Station in Truckee is approximately 2 hours from Davis. It also the site of Professor Phil Ward's popular "Bug Boot Camp."