- Author: Kathy Keatley Garvey
Chen, an associate project scientist, will discuss the emerald ash borer and the goldspotted oak borer and their interactions with their host plants. His talk is from 12:10 to 1 p.m. in 122 Briggs Hall.
Research entomologist Steve Seybold of the USDA's Forest Service and an affiliate of the Department of Entomology and Nematology is the host.
Chen, who holds a master's degree in applied statistics (2010) from Michigan State University, obtained his doctorate in entomology from the University of Georgia in 2007. For his dissertation research, he investigated various effects of nitrogen fertilization on tritrophic interactions among cotton plants, the beet armyworm, Spodoptera exigua, and the parasitoid, Cotesia marginiventris. The project integrated ecological, chemical, nutritional, and behavioral elements to evaluate the role of nitrogen in shaping tri-trophic interactions in cotton.
Chen carried out postdoctoral research at Michigan State University's Department of Entomology from 2008 to 2011 on the behavioral, chemical, and nutritional interactions between the invasive emerald ash borer, Agrilus planipennis, and ash trees. He relocated to UC Davis in July 2011 to lead an effort to improve trapping lures for detection of another invasive pest, the goldspotted oak borer, Agrilus auroguttatus.
In collaboration with research entomologists from the USDA Forest Service, Chen is now working to develop management options for the invasive walnut twig beetle, Pityophthorus juglandis, and polyphagous shot hole borer, Euwallacea sp.
Chen's overarching research goals are to build arthropod pest management systems that emphasize naturally occurring pest suppression agents and environmentally friendly tactics, that is, insect sex pheromones and other semiochemicals, in a holistic, ecosystem-based approach. He is also interested in studying pest population dynamics in the context of various pest management tactics, agronomic practices, and abiotic environmental factors (e.g., temperature and precipitation) with mathematical and statistical tools.
Wednesday, Oct. 8
Vaughn Walton
Associate professor and Extension entomologist
Lead investigator, Spotted Wing Drosophila Project
Oregon State University
Title: "Complexities Associated with Two Invasive Pests: Challenges and Opportunities"
Hosts: Assistant professor Joanna Chiu and distinguished professor Frank Zalom, Department of Entomology and Nematology
Wednesday, Oct. 15
Surendra Dara
Strawberry and Vegetable Crops and affiliated IPM Advisor, University of California Cooperative Extension, San Luis Obispo, Santa Barbara, and Ventura counties.
Title: "Thinking Outside the Cubicle to Provide Practical Solutions to the Farmers"
Host: Michael Parrella, professor and chair of the Department of Entomology and Nematology
Wednesday, Oct. 22
Blaine Cole
Professor, University of Houston, specializing in evolution, ecology and behavior.
Title: "Colony Growth and Fitness in Harvester Ants"
Host: Marshall McMunn, graduate student, Louie Yang lab, Department of Entomology and Nematology
Wednesday, Oct. 29
Clifford Ohmart
Entomologist and vice president of professional services
SureHarvest, sustainable agriculture
Title: "Sustainable Agriculture: What Is Happening Out on the Farm?"
Host: Michael Parrella, professor and chair of the Department of Entomology and Nematology
Wednesday, Nov. 5
Chuck Fox
Professor, University of Kentucky, specializing in ecology and evolution of life histories; insect-plant interactions; insect behavioral ecology
Title: "Inbreeding-Environment Interactions: Experimental Studies and a Meta Analysis"
Host: Jay Rosenheim, professor, Department of Entomology and Nematology
Wednesday, Nov. 12
Louie Yang
Assistant professor, UC Davis Department of Entomology and Nematology, specializing in ecology
Title: "Pulses, Phenology and Ontogeny: Towards a More Temporally Explicit Framework for Understanding Species Interactions?"
Wednesday, Nov. 19
Ray Hong
Associate professor of biology, California State University, Northridge, specializing in nematology
Title: “A Fatal Attraction: Regulation of Development and Behavior in the Nematode Pristionchus pacificus by a Beetle Pheromone”
Host: Valerie Williamson, professor of nematology, Department of Entomology and Nematology
Wednesday, Nov. 26
Doris Bachtrog, lab
Associate professor, UC Berkeley, specializing in evolutionary and functional genomics
Title: "Numerous Transitions of Sex Chromosomes in Diptera"
Host: Michael Parrella, professor and chair, Department of Entomology and Nematology
Wednesday, Dec. 3
To be announced
Wednesday, Dec. 10
Sawyer Fuller
Postdoctoral researcher, Harvard University
Title: "RoboBee: Using the Engineering Toolbox to Understand the Flight Apparatus of Flying Insects"
Host: James Carey, distinguished professor of entomology
This seminar by Sawyer Brown will be remote broadcast to UC Davis.
Plans call for recording the seminars, coordinated by Professor James Carey, for later posting on the web.
- Author: Kathy Keatley Garvey
Yigen Chen and Steve Seybold continually trapped the reddish-brown insect, about a third of the size of a grain of rice, for three years along Putah Creek in Davis, Calif., and recorded its daily and seasonal flight behavior. They lured the insect into the traps with a synthetic version of its aggregation pheromone.
“We discovered the collective and interactive effects of four environmental factors on the crepuscular (twilight) flight behavior of the insect,” said lead author Chen, a research entomologist and project scientist with the UC Davis Department of Entomology and Nematology. “We found that the optimal trapping conditions are a combination of moderate to warm temperatures, around 79 to 81 Fahrenheit; low light intensity; low wind speed, 0.6 to 2.5 miles per hour; and moderate barometric pressure, 755 to 757.”
“Understanding the walnut twig beetle's seasonal flight cycle and factors that govern its flight are critical first steps in the early detection of invasive species prior to implementing pest eradication or integrated pest management (IPM) programs,” they wrote in their research article, “Crepuscular Flight Activity of an Invasive Insect Governed by Interacting Abiotic Factors,”published in the Aug. 26 edition of the Public Library of Science, PLOS ONE.
However, when coupled with a hitchhiking fungus, Geosmithia morbida, it causes what is known as thousand cankers disease. The beetles create numerous galleries beneath the bark, resulting in fungal infection and canker formation. The large numbers of cankers led to the name, thousand cankers disease.
As the disease advances, the health of the tree declines and eventually it dies, sometimes within a three-year period, said Seybold, who has been studying the beetle and the newly discovered fungus with its barrel-shaped spores since 2008.
When male beetles initiate new galleries, they produce an aggregation pheromone. As the population increases, the flight response of males and females similarly increases.
Mating disruption or interruption of insect aggregation is crucial to controlling such insect pests as the walnut twig beetle in IPM programs, the entomologists pointed out. “Understanding the interactions among abiotic environmental factors on flight activity, should increase the efficacy of these methods in a specific IPM program to control the beetle,” Chen said.
“The primarily crepuscular flight activity had a Gaussian relationship with ambient temperature and barometric pressure but a negative exponential relationship with increasing light intensity and wind speed,” they wrote in their abstract. “A model selection procedure indicated that the four abiotic factors collectively and interactively governed P. juglandis diurnal flight.”
New knowledge of the primary periods of seasonal flight (May‒July and September‒October) “provides some guidance for when semiochemical-based interruption of aggregation may be applied most efficaciously,” they said..
Seybold, one of the first scientists to study the beetle and fungus in California, served on a scientific team that developed guidelines and trapping methods for the beetle. In 2010 and 2011, the team discovered and later patented the aggregation pheromone for the beetle and conducted scientific trials in northern California.
Late in the summer of 2011, the team demonstrated the efficacy of the pheromone as a flight trap bait. The bait lures both male and female beetles into a small plastic funnel trap.
The walnut twig beetle, native to the southwestern United States and Mexico, and widely distributed in Colorado, Arizona, California, and New Mexico, has now been detected throughout much of the United States: in nine western and five eastern states. In 2013, it was reported in northern Italy.
The earliest symptom of thousand cankers disease is yellowing foliage that progresses rapidly to brown wilted foliage, then finally branch mortality. Branch mortality and decline of the tree crown are one of three major symptoms of thousand cankers disease. The others are numerous small cankers on branches and the trunk, and holes and other evidence of tiny bark beetles.
Related links:
- Thousand Cankers Disease and the Walnut Twig Beetle in California (UC IPM)
- Walnut Twig Beetle (USDA Forest Service)
- Pest Alert, Walnut Twig Beetle and Thousand Cankers Disease (Colorado State University)
- Thousandcankers.com (This site is a collaborative effort between the Northeastern Area State and Private Forestry, the USDA Forest Service Northern Research Station, the Purdue University Department of Forestry and Natural Resources, the Hardwood Tree Improvement and Regeneration Center, the American Walnut Manufacturers Association, and the Walnut Council.)