It's about 150 years old, 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 is causing 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?
"Bee" sure to tune in Science Friday, the National Public Radio program, tomorrow (May 24) at noon to hear the buzz about honey bees.
Guests will be Extension apiculturist Elina Lastro Niño of the UC Davis Department of Entomology and Nematology, Professor Tom Seeley, bee scientist, researcher and author, of Cornell University, Ithaca; and New York city police officer and beekeeper Darren Mays, who keeps hives on the roof of the 104th precinct.
Ira Flatow hosts the popular program. Senior producer Christopher Intagliata said plans call for introducing Seeley at the top of the hour, and then bringing in Niño around 12:30. Officer Mays will be introduced at 12:40.
Elina Lastro Niño
Niño, who joined the UC Davis Department of Entomology and Nematology in 2014 from Pennsylvania State University, researches honey bee biology, health, reproduction, pollination biology, insect ecology, evolution, genomics and chemical ecology, and genomics. She directs the California Master Beekeeper Program and the Häagen-Dazs Honey Bee Haven, a half-acre bee garden located next to the Harry H. Laidlaw Jr. Honey Bee Research Facility on Bee Biology Road.
Born and reared in Bosnia in Eastern Europe, Elina moved to the United States with plans to become a veterinarian. She obtained her bachelor's degree in animal science at Cornell University, Ithaca, N.Y., but while there, enrolled in an entomology class on the recommendation of her adviser. “I was hooked,” she recalled.
Following her graduation from Cornell in 2003, she received her master's degree in entomology from North Carolina State University and her doctorate in entomology from Pennsylvania State University. She then served as a postdoctoral fellow in the honey bee lab of Christina Grozinger, who studies the genomics of chemical communication.
Seeley is the Horace White Professor in Biology, Department of Neurobiology and Behavior, Cornell University. He joined the faculty of Cornell in 1986 and holds a doctorate in biology from Harvard.
A frequent speaker at UC Davis, keynoted the 2018 UC Davis Bee Symposium. In his address on "Darwinian Beekeeping," Seeley commented: "EVERYTHING that colonies do when they are living on their own (not being managed by beekeepers) is done to favor their survival and their reproduction, and thus their success is contribution to the next generation of colonies. And I mean everything."
Seeley says that is scientific work primarily focuses on "understanding the phenomenon of swarm intelligence (SI): the solving of cognitive problems by a group of individuals who pool their knowledge and process it through social interactions. It has long been recognized that a group of animals, relative to a solitary individual, can do such things as capture large prey more easily and counter predators more effectively. More recently it has been realized that a group of animals, with the right organization, can also solve cognitive problems with an ability that far exceeds the cognitive ability of any single animal. Thus SI is a means whereby a group can overcome some of the cognitive limitations of its members. SI is a rapidly developing topic that has been investigated mainly in social insects (ants, termites, social wasps, and social bees) but has relevance to other animals, including humans. Wherever there is collective decision-making—for example, in democratic elections, committee meetings, and prediction markets—there is a potential for SI."
Seeley is the author of numerous books, including Honeybee Ecology: A Study of Adaptation in Social Life, Princeton University Press; The Wisdom of the Hive: The Social Physiology of Honeybee Colonies. Harvard University Press; Honeybee Democracy. Princeton University Press, Following the Wild Bees: The Craft and Science of Bee Hunting. Princeton University Press; and The Lives of the Bees: The Untold Story of Honey Bees in the Wild, Princeton University Press.
Mays is a well-known rooftop beekeeper. According to a 2018 article in the Business Insider, he "gained temporary fame this summer when he vacuumed up a migrating swarm of bees that perched atop a hot dog cart umbrella in Times Square." At night, he patrols the streets of Queens, and by day, he keeps the bees.
"Mays and another officer, Michael Lauriano, are responsible for responding to any issue a New Yorker calls in with that involves a 'stinging insect.' He said he responds to about a dozen calls during a typical summer, as people request help with bee swarms, wasps nests, and more. Before Mays and Lauriano, an officer named Anthony 'Tony Bees' Planakis served as the NYPD's first bee 911 responder."
Have you ever seen the larva of a lady beetle (aka ladybug) dining on an aphid?
Lights! Camera! Action!
So here is this charming little immature lady beetle chowing down on an oleander aphid that has the audacity to infest the milkweed in our pollinator garden. Chomp! Crunch! Slurp! And then another aphid arrives on the scene. It does not flee. Aphids are not the smartest of insects.
Can you just wait! Hold on! I'm not finished eating this one, yet!
And then an adult lady beetle arrives. She ignores a fat aphid right before her very eyes. Shall we prey?
Can you just wait! Don't go away! I'll eat you when I'm hungry!
A lady beetle (it's not a bug, it's a beetle!) belongs to the family Coccinellidae. Scientists have described about 5000 species worldwide, and about 450 in North America.
How many aphids can a lady beetle eat in her lifetime of three to six weeks? An estimated 5000 aphids, according to the University of Kentucky Cooperative Extension Service.
That's great pest control!
One thing is for sure: the lady beetles and their offspring patrolling our milkweed plants will never experience famine. This is an all-you-can-eat buffet, and the aphids just keep on a'coming. They do not flee. Aphids are not the smartest of insects.
Now, where are the monarchs? We have milkweed waiting./span>
And this one, too.
And that one over there!
When UC Davis employees and their offspring visited the Bohart Museum of Entomology during the recent "Take Your Daughters and Sons to Work" Day, reactions ranged from awe to "wow!"
They held walking sticks (stick insects), Madagascar hissing cockroaches and tomato hornworms. Two youngsters held tarantulas. And all checked out the butterfly and beetle specimens.
One little girl, Olivia Bingen, 4, who was there with her father, Steve Bingen of the UC Davis Department of Music, was dressed in pink and asked the Bohart scientists if they had any pink butterflies.
"She likes pink," her father said. She also likes to play the violin.
The museum, founded in 1946 by the late Richard M. Bohart and now directed by Lynn Kimsey, UC Davis professor of entomology, is open to the public from 9 a.m. to noon and from 1 to 5 p.m., Mondays through Fridays, except on holidays. Admission is free.
Special weekend events, free and family friendly, are held throughout the year. The next weekend event is Moth Night from 8 p.m. to 11 p.m. on Saturday, Aug. 3. Blacklighting will take place just outside the museum. Inside, the attendees will visit the museum's displays and, outside, they will see what insects are attracted to the black-lighted white sheets.
Among those scheduled to host Moth Night are John "Moth Man" DeBenedictis; senior museum scientist Steve Heydon; entomologist Jeff Smith, who curates the Lepitopdera (butterflies and moths) section of the Bohart; and Greg Kareofelas, Bohart associate and naturalist.
We celebrate honey bees every day, but they are especially celebrated on May 20, World Bee Day. It's an annual day to raise awareness about the importance of bees and beekeeping. It's a day to acknowledge the industriousness of Apis mellifera, their role in our lives, and their place in our ecosystem. Bees pollinate a third of the food we eat.
A bit of history: The United Nations approved Slovenia's proposal to proclaim May 20 as World Bee Day in December of 2017. Slovenia also sought to pay tribute to noted beekeeper and native son Anton Janša (1734-1773) of Carniola (now Slovenia), a pioneer of modern apiculture, a noted painter, and an apiculture teacher at the Habsburg Court in Vienna.
Janša became a full-time beekeeper in 1769. He began by tending his father's 100 hives, but a year later, he received a royal appointment as Austria's teacher of apiculture. He kept bees in the imperial gardens (Augarten) and traveled the country, eager to present information about his beloved bees.
Janša "became famous for his lectures in which he demonstrated his knowledge of bees," according to Wikipedia. "He also wrote two books in German: Discussion on Beekeeping and A Full Guide to Beekeeping. The latter was published in 1775, after his death. In Full Guide, Janša noted: Bees are a type of fly, hardworking, created by God to provide man with all needed honey and wax. Amongst all God's beings there are none so hard working and useful to man with so little attention needed for its keep as the bee."
A tip of the veil to Anton Janša!
More locally, the Häagen-Dazs Honey Bee Haven, part of the UC Davis Department of Entomology and Nematology, celebrated bees during the "Take Our Daughters and Sons to Work" Day. UC Davis employees and their offspring visited the half-acre garden on Bee Biology Road, admiring the flowers and the six-foot-long bee sculpture, Miss Bee Haven, that anchors the garden. The ceramic-mosaic sculpture is the work of Donna Billick of Davis, a self-described "rock artist."
Anton Janša would have felt right at home!
Among the bee haven visitors that day were two beekeepers: elementary school student Adelaide Grandia of Woodland and her grandfather Dwight Grandia of Gulf Shores, Alabama, who has kept bees for 39 years. "I've had hives in the Atlanta area for 25 years and in northern Alabama for 10 years," he said. "I'm teaching my granddaughter beekeeping." He recently set up a bee hive for her.
"My grandpa is a beekeeper," Adelaide said, "and a pilot." Her mother, UC Davis Professor Liza Grandia of Native American Studies, is also interested in bees.
David Hernandez, who works in the Facilities Management Steam Shop, brought his sons, Aayden, 10, and Evan, 8. They checked out the garden, installed in the fall of 2009, and gathered for a photo behind the pollinator cut-out board, as did colleague Kris McBride of the Facilities Management Steam Shop and son, Deegan, 4-1/2.
UC Davis staff employee Xu Chunying and son, Andy, delighted in the catch-and-release activity, in which youths catch bees in a vacuumlike tube device, examine them, and then release them. Honey bees, native bees and carpenter bees are favorite subjects.
Ariel Cormier, who works in the Office of the Chancellor and Provost as manager of Budget and Financial Analysis, attended with her eight-year-old twin daughters Casey and Gabrielle. They delighted in the bees, blossoms, and the beautiful day.
The Häagen-Dazs Honey Bee Haven, located next to the Harry H. Laidlaw Jr. Honey Bee Research Facility, is open to the public from dawn to dusk. Admission is free. Group tours are also available for a small charge. For more information, access the website.