It's about the size of a grain of rice but it's a killer.
That's the walnut twig beetle, Pityophthorus juglandis, which in association with a newly described fungus, Geosmithia morbida, causes thousand cankers disease, wreaking havoc on native black walnut trees.
Enter doctoral student Jackson Audley of the Steve Seybold lab, UC Department of Entomology and Nematology. He will present a seminar on "Protecting Trees from Bark Beetle Attacks Utilizing Semiochemical Repellents: A Case Study with the Walnut Twig Beetle” at a seminar from 4 to 5 p.m., today (Wednesday, Oct. 25) in Room 3001 of the Plant and Environmental Science Building.
The seminar is part of the UC Davis Forest Biology Research Center Seminar Series and his presentation is a preview of his thesis project.
"In this talk I will discuss the theoretical construct of semiochemical repellents for protecting trees from attack by bark beetles and demonstrate the process of developing a repellent tool with my work on the walnut twig beetle, Pityophthorus juglandis, the vector of thousand cankers disease in walnuts," Audley says in his abstract. "Bark beetles can constitute a significant threat to tree health and are a significant disturbance agent in forest ecosystems. Semiochemicals have been successfully utilized to protect individual to stands of susceptible trees from various bark beetle pests. Most of this work has been conducted in coniferophagous bark beetle systems. My work here at UC Davis has been focused on bringing those same techniques into studying an invasive, hardwood-attacking bark beetle system."
Audley received his bachelor's degree in wildlife biology and natural resource recreation and tourism in 2009 from the University of Georgia, and his master's degree in forestry in 2015 from the University of Tennessee. As a master's student, he did research on the walnut twig beetle, including treatment tests.
The walnut twig beetle is believed to be native to Arizona, California, New Mexico and Mexico. In 2006, plant pathologist Ned Tisserat and entomologist Whitney Cranshaw of Colorado State University identified the pathogen in declining black walnut trees in central Colorado. The disease has now spread throughout much of the United States.
"Often the first symptoms of thousand cankers disease (TCD) are flagging and yellowing leaves and branch dieback," says Seybold, one of the pioneering TCD researchers. He is a chemical ecologist with the USDA Forest Service, Pacific Southwest Research Station, Davis, and a lecturer/researcher with the UC Davis Department of Entomology and Nematology. "Affected branches show sap staining and pinhole-sized beetle holes. Beneath the surface are dark stains caused by the fungus."
"The fungus enters the tree through the feeding or reproductive activities of the beetle, and colonizes and kills the phloem and cambium of the branches and main stem," according to the UC Integrated Statewide Integrated Pest Management Program website, content that's the work of Steve Seybold and entomologist Mary Lou Flint, then associate director of of Urban and Community IPM, and now UC Extension entomologist emerita. The disease gets its name from the large number of dark cankers that rapidly develop on affected branches.
The UC Davis Forest Biology Research Seminars, which began Oct. 11, are held Wednesdays at 4 p.m. in Room 3001 of the Plant and Environmental Science Building.
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”
For more information, contact David Neale at email@example.com.
UC Davis entomology doctoral student Stacy Hishinuma has received and accepted a position in the USDA Pathways Internship Program with the Region 5 field office of the USDA Forest Service, San Bernardino.
Hishinuma studies the walnut twig beetle, Pityophthorus juglandis, which in association with a newly described fungus, Geosmithia morbida, causes thousand cankers disease (TCD) of walnut and butternut trees.
The walnut twig beetle is believed to be native to Arizona, California, New Mexico and Mexico. In 2006, plant pathologist Ned Tisserat and entomologist Whitney Cranshaw of Colorado State University identified the pathogen in declining black walnut trees in central Colorado. The disease has now spread east of the Mississippi to states in the heart of the valuable black walnut timberlands. Most recently it was reported from Indiana. Latest collection records show that the beetle and pathogen are now known from nine states in the western United States and seven states in the eastern USA. In 2013 the disease was also reported in Italy marking the first time that it occurred in Europe.
Hishinuma works with major professor Mary Louise Flint and is co-advised by chemical ecologist and forest entomologist Steve Seybold of the Pacific Southwest Research Station, USDA Forest Service, Davis, an affiliate of the department. Flint is an Extension specialist emeritus with the UC Davis Department of Entomology and Nematology and a former associate director with the UC Integrated Pest Management Program.
“USDA will provide some financial support during the end stages of her Ph.D. thesis, in exchange for 320-640 hours of work and training over the next 14 months,” said Seybold. Then, in June 2016 her position will be converted to that of a permanent entomologist with the USDA Forest Service office in San Bernardino after she has completed her thesis. She will be responsible for forest insect survey, detection, and management on four national forests in southern California ranging from San Diego to Monterey counties.
“The highly competitive internship and guaranteed position are a credit to her and her achievements,” Seybold said.
Seybold and Flint assisted her in developing the internship, as did Richard “Rick” Bostock, UC Davis professor of plant pathology.
Hishinuma won the 2013 Western Forest Insect Work Conference Memorial Scholarship for her research on TCD and presented her work at group's 65th annual conference, held March 31-April 3, 2014 in Sacramento. She also received two scholarships from the California Garden Clubs, Inc. (CGCI) and a McBeth Memorial Scholarship to support her research on TCD.
Seybold's research group has led the effort to characterize the disease in California and to develop a nationwide detection program for the beetle. They recently published two papers in the journal PLOS ONE that characterize the genetic diversity and invasion patterns of both the pathogenic fungus and the beetle in the United States. Scientists believe that TCD occurs only on walnut, butternut, and wingnut, but it is most damaging to native black walnuts, Juglans californica, J. hindsii, and J. nigra although the disease has been recorded on at least 10 species of walnuts or their hybrids in California. Often the first symptoms of TCD are flagging and yellowing leaves and branch dieback, Seybold said. Affected branches show sap staining and pinhole-sized beetle holes. Beneath the surface are dark stains caused by the funguhe news is startling, but not totally unexpected.
No wonder. The insect, measuring about 1.5 millimeters long, is much smaller than a grain of rice.
Now, however, they can see a teddy-bear-sized version, thanks to a University of California, Davis entomology major Kristina Tatiossian, a member of the Research Scholars Program in Insect Biology.
Through the UC Davis Art/Science Fusion Program, Tatiossian, a junior, crafted a ceramic mosaic sculpture of the tiny walnut twig beetle for her research poster, “Flight Response of the Walnut Twig Beetle, Pityophthorus juglandis, to Aggregation Pheromones Produced by Low Densities of Males.”
The beetle jutting from the poster is so true to form that scientists studying the insect not only readily recognize it, but point out that it’s a female. That includes her mentor, chemical ecologist and forest entomologist Steve Seybold of the Davis-based Pacific Southwest Research Station, USDA Forest Service, and an affiliate of the UC Davis Department of Entomology.
Seybold and Andrew Graves, a former UC Davis researcher with the UC Davis Department of Plant Pathology, who now works for the USDA Forest Service, first detected the newly recognized beetle-fungus disease, known as Thousand Cankers Disease (TCD), in California in 2008. TCD had been detected earlier in Colorado and its impact had been noted even earlier in New Mexico, Oregon, and Utah. TCD and its history are chronicled in a newly revised “Pest Alert” issued by the USDA Forest Service.
Tatiossian accomplished the research project as part of the Research Scholars Program in Insect Biology, which aims to provide undergraduates with a closely mentored research experience in biology. Headed by professor Jay Rosenheim, and assistant professor Louie Yang of the UC Davis Department of Entomology, the program currently has 12 students; students apply when they are freshmen, sophomores or transfer students. Tatiossian joined the program in 2011 and is mentored by Steve Seybold.
Tatiossian completed the ceramic mosaic project over a four-week period. She earlier worked on two UC Davis Art/Science Fusion Program projects, including the “Tree of Life,” with the program’s founders, entomologist/artist Diane Ullman and artist Donna Billick. A former Los Angeles resident, Tatiossian will receive her bachelor’s degree in entomology this June and then plans to attend graduate school to study either biochemistry or virology.
Tatiossian will giving an oral presentation on her research at the Pacific Branch, ESA meeting, set for April 7-10 at South Lake Tahoe. Then she will display the poster again in the Undergraduate Research Conference at UC Davis on April 24 in Wellman Hall.
By itself, the beetle, native to Arizona, California, New Mexico and Mexico, does little or no damage. But when coupled with the newly described fungus, Geosmithia morbida, it is killing thousands of walnut trees.
The disease is creating havoc throughout much of the western United States, Seybold said, and is now heading east. Its primary host is the black walnut tree but it also attacks other walnut trees.
“Male WTB initiate new galleries and produce an aggregation pheromone, which can be used to study patterns of initial host colonization behavior of WTB. It has been previously shown by Graves and colleagues (2010) that as the number of males in a branch is increased from 20 to 200, the flight response of males and females is similarly increased,” she wrote. “We investigated flight responses to lower numbers of males in cut branch sections of northern California black walnut, Juglans hindsii.”
Her objective: “To determine the minimum number of males in an artificially infested branch of Juglans hindsii necessary to elicit a flight response from WTB.” She found that as little as one to five males is enough to elicit the aggregation response at her field study sites at two locations in Davis.
The poster will be displayed on the third floor of Briggs Hall, just outside the Department of Entomology’s administration office.
On her poster, Tatiossian credits Seybold; Extension entomologist Mary Louise Flint, associate director for Urban and Community IPM, UC Statewide Integrated Pest Program; entomology graduate student Stacy Hishinuma, and postdoctoral researcher Yigen Chen of the UC Davis Department of Entomology.
And the UC Davis Art/Science Fusion Program where the tiny walnut twig beetle sprang to life.
Chemical ecologist and forest entomologist of Steve Seybold of the USDA Forest Service, Pacific Southwest Research Station, Davis, Calif., and a faculty affiliate of the UC Davis Department of Entomology, is leading a research group to characterize the disease in California.
A new member of the team is UC Davis entomology graduate student Stacy Hishinuma (right), who just received a McBeth Memorial Scholarship to help fund her research.
TCD is caused by the walnut twig beetle, Pityopthorus juglandis, in association with a newly described fungus, Geosmithia morbida.
“The beetle is believed to be native to Arizona, California, New Mexico and Mexico,” Hishinuma said, “but was never associated with walnut tree mortality until just recently.”
The disease was first noticed in canker-riddled black walnuts in Utah and Oregon in the early 1990s, but scientists attributed that to environmental stress. In 2006, plant pathologist Ned Tisserat and entomologist Whitney Cranshaw of Colorado State University identified the pathogen in declining black walnut trees in central Colorado. TCD is now found in eight western states (Arizona, California, Colorado, Idaho, New Mexico, Oregon, Utah and Washington), plus Tennessee.
“My project focuses on understanding more about the biology of the beetle and fungus and documenting the frequency and progression of TCD in various walnut species throughout California,” Hishinuma said. “The McBeth scholarship is funding my travel to field sites across California.”
Hishinuma, who is seeking her master’s degree in entomology, works with major professor and integrated pest management (IPM) specialist Mary Lou Flint and is co-advised by Seybold. Flint, with the statewide UC IPM Program, is the associate director for urban and community IPM, and a Department of Entomology extension specialist.
The fungus enters the tree when the beetle tunnels into the bark to prepare egg galleries. “The fungus is probably carried as conidia on the beetle’s elytra or wing covers,” said Seybold, who has been studying the chemical ecology and behavior of bark beetles for more than 25 years.
Scientists believe that TCD occurs only on walnut, predominantly native black walnut, Juglans californica and J. hindsii, although the disease has been recorded on 10 species of walnuts or their hybrids in California. Often the first symptoms of TCD are flagging and yellowing leaves and branch dieback, Seybold said. Affected branches show sap staining and pinhole-sized beetle holes. Beneath the surface are dark stains caused by the fungus.
A tree can survive the stress produced by a few cankers, but when high populations of the beetle enter the tree and the numerous small cankers coalesce, the disease girdles twigs and branches. Eventually TCD attacks the main stem of the weakened tree down to the soil line.
Last summer, a USDA/UC Davis research team began tracking the pathogen and the beetle throughout the state, particularly in commercial orchards.
To prevent spread, infected trees should be removed and destroyed immediately by grinding or burning to ensure that beetles are destroyed, Seybold said. Infested walnut for chips, firewood, or woodworking should not be moved to new areas. Possible detections can be reported to the local agricultural commissioner’s office or to the local UC Cooperative Extension office.
Hishinuma, from Burbank, completed her undergraduate work at UC Davis in animal biology, with an entomology emphasis. She began her graduate studies this fall after working for a year in southern California assisting with research on the goldspotted oak borer, a relatively new pest in southern California that kills oak trees. Beetle-infested firewood contributes to the problem, as it does with thousand cankers disease.
The McBeth Memorial Scholarship was established in 1986 by Barbara McBeth Woodruff (1924-2007) in honor of her parents, Ira Guy McBeth and Rose McBeth, and her sister Frances McBeth Black. Ira Guy McBeth, an entomologist who received his doctorate from the University of California in 1915, made notable contributions to the citrus industry and served as an executive in agricultural, chemical and development companies.
Meanwhile, a thousand questions about thousand cankers disease...and maybe soon...solutions.
Steve Seybold discussed thousand cankers disease in a seminar presented May 19, 2010 to the UC Davis Department of Entomology. The seminar was webcast and is archived on the entomology website. (USDA Forest Service Pest Alert on Thousand Cankers Disease of Walnut (targeting eastern U.S. region). (May 2010)
UC IPM website (Authors: Andrew Graves, postdoctoral researcher, formerly with the UC Davis Department of Plant Pathology; Mary Louise Flint, UC IPM Program and Department of Entomology, UC Davis; Tom Coleman, USDA Forest Service, Forest Health Protection, San Bernardino; and Steven Seybold, USDA Forest Service, Pacific Southwest Research Station, Davis)
Detected in Tennessee (News release, Aug. 9, 2010, UC Davis Department of Entomology website)
Detected in California (News release, July 2, 2010, UC Davis Department of Entomology website)
That quote sound familiar? Chemical ecologist Jacques Le Magnen (1916-2002) said that back in 1970.
World-renowned organic chemist Wittko Francke (right) of the University of Hamburg, Germany, called attention to Le Magnen's quote at a UC Davis Department of Entomology seminar on Wednesday noon, Dec. 8.
It bears repeating: "Nature is more a world of scents than a source of noise."
Insects communicate in a chemical language or chemical signals, Francke told the crowd.
Indeed, scientists have long known that methods that can attract or repel insects have important applications for agricultural pests and medical entomology.
Francke told how a queen bee secretes compounds that regulate development and behavior of the colony, and how an orchid releases the scent of a female wasp to attract male wasps— a scent that results in pollination. He also touched on the “calling cards” of a number of other insects, including bumble bees, wasps, pea gall midges, stingless bees, bark beetles and leafminers. He pointed out that that plants, too, send chemical signals.
UC Davis graduate students James Harwood and Amy Morice of the James R. Carey lab video-taped the seminar. It will be online soon at http://entomology.ucdavis.edu/news/webcastlinks.html
Francke was introduced by chemical ecologist-forest entomologist (and UC Davis Department of Entomology affiliate) Steve Seybold of the USDA Forest Service, Pacific Southwest Research Station, Davis.
No stranger to UC Davis, Francke previously collaborated with chemical ecologist Walter Leal, professor and former chair of the UC Davis Department of Entomology, on attractants for navel orangeworm.
In his talk, Francke mentioned Leal’s discovery of a sophisticated mechanism for the isolation of the chemical communication channels of two species of scarab beetles.
Seybold and Francke are collaborating on the chemical signals of the walnut twig beetle, which in association with a newly described fungus, causes thousand cankers disease, a killer of walnut trees.
Thousand cankers disease (TCD) is now found in seven western states, plus Tennessee. Seybold is a key researcher in California.
Scientists believe that TCD occurs only on walnut, predominantly native black walnut, Juglans californica and J. hindsii, although the disease has been recorded on 10 species of walnuts or their hybrids in California.
Often the first symptoms of TCD are flagging and yellowing leaves and branch dieback, said Seybold, who has been studying the chemical ecology and behavior of bark beetles for more than 25 years. Affected branches show sap staining and pinhole-sized beetle holes. Beneath the surface are dark stains caused by the fungus.
A USDA/UC Davis research team is tracking the pathogen and the beetle throughout California, particularly in commercial orchards.
That all points back to “Nature is more a world of scents than a source of noise.”