A male metallic green sweat bee in flight. (Photo by Kathy Keatley Garvey)

What was that foraging on a pink iceplant blossom near a path to the ocean? A metallic green sweat bee, Agapostemon texanus, also called an ultra green sweat bee.

We usually don't see A. texanus unless it's spring or summer, but there it was, out of season. Or rather, there "he" was. Males and females are easily distinguishable.  The female is solid green, from head to thorax to abdomen, while the green coloration on the male appears on the head and thorax. 

We remember pollinator specialist Robbin Thorp (1933-2019) emeritus professor of entomology at UC Davis, talking about them. He delighted in seeing them at his monitoring site, the Department of Entomology and Nematology's Häagen-Dazs Honey Bee Haven on Bee Biology Road,  UC Davis campus. The Agapostemon are members of the Halictinae family. They are often called "sweat bees" because they are attracted to human sweat, probably for the salt.

Green sweat bees are among the bees featured in the book, "California Bees and Blooms: A Guide for Gardeners and Naturalists," co-authored by the University of California team of Gordon Frankie, UC Berkeley; Robbin Thorp,  UC Davis; and UC Berkeley affiliates Rollin Coville (photographer and entomologist) and Barbara Ertter (plant specialist). Frankie, Thorp, Coville and Ertter (and others) also published "Native Bees Are a Rich Natural Resource in Urban California Gardens" in California Agriculture.

Robert Washino, medical entomologist, emeritus professor, and U.S. Army veteran

When you say "Thank you for your service," that not only means his service in the Korean War, but his entire career in medical entomology.

Dr. Washino, an emeritus professor/chair of the UC Davis Department of Entomology (now the Department of Entomology and Nematology), is internationally known for his expertise in medical entomology and ecology, more specifically the ecology of mosquitoes and mosquito control agents; rice field ecology; mosquito blood meal identification, and remote sensing and geographic information technologies. He co-authored the last complete treatise on the Mosquitoes of California.

He is legendary for not only his research, but for his academic, administrative, and public service accomplishments. 

However, few people know that during the Korean War, the Sacramento native served as a lieutenant in the U.S. Army Medical Service Corps from 1956 to 1958. He saw duty in Europe (Orléans, France). As a medical entomologist, Lt. Washino conducted a small detachment and a laboratory and later served as an assistant preventative medicine officer.

And even fewer people are aware that as a child, he was incarcerated with his family in American-Japanese internment camps from 1942 to 1945. It was a sad time in American history. On Feb. 19, 1942, President Franklin D. Roosevelt signed Executive Order 9066, sending nearly 120,000 American citizens and legal residents of Japanese descent to internment camps. Young Bob was 10 years old and living in Sacramento with his parents and four older sisters when the mandate took effect.  The family eventually returned to Sacramento. 

Young Bob went on to graduate from a Sacramento high school, receive his bachelor's degree in public health (1954) from UC Berkeley; and two entomology degrees from UC Davis: a master's degree (1956) and a doctorate (1967).  He joined the entomology faculty in 1964. He officially retired in 1993, but continued his academic, research and public service accomplishments into his early 80s. He still consults with the medical entomologist community, including prospective students.

As an emeritus professor, Dr. Washino was called back into service. He accepted a total of three administrative posts on the UC Davis campus: special assistant to the dean of the College of Agricultural and Environmental Sciences; interim co-director of the Center for Vectorborne Diseases, School of Veterinary Medicine; and chair of the entomology department.

Dr. Washino served 38 consecutive years on the Sacramento-Yolo Mosquito and Vector Control (SYMVC) Board,  the longest in the agency's history.This included five terms as president. He was instrumental in spearheading plans for the design and development of the present 40-acre district complex, completed in 1994. The building that houses the laboratory, laboratory staff and the library is named in his honor. In fact, he not only designed the complex, but gifted his literature and photographic collection for research and teaching purposes. 

Among his dozens of credentials:

• Past president of the American Mosquito Control Association and the California Mosquito and Vector Control Association
• Former director of the UC Agricultural and Natural Resources Statewide Center for Pest Management and a consultant with the USDA Cooperative State Research Service.
• Coordinator of an international symposium on “Culex pipiens Complex Symposium: Global Perspectives in the 21st Century” in Anaheim, Orange County, Calif., gathering together 17 U.S. and worldwide speakers, including experts from London, Japan, Australia, Portugal and Germany.   This was part of the four-day American Mosquito Control Association conference. He published the results of this landmark symposium on Dec. 2, 2012 in the Journal of the American Mosquito Control Association; see https://bioone.org/journals/journal-of-the-american-mosquito-control-association/volume-28/issue-4s.  The publication serves as a general landmark of how mosquito biologists currently view the Cx. pipiens complex. At the time, understanding the systematics of the Culex pipiens complex was one of the most controversial topics in the mosquito world.  
• Chairman of the UC Davis Contained Research Facility Committee, resulting in the establishment of containment facilities on the UC Davis and UC Riverside campuses to solve the critical demand for strengthened pest exclusion, early detection, and alternative strategies for managing pest and disease problems. During the process, he worked with entomology, plant pathology and nematology faculty and with infrastructure officials on the two campuses.

Highly honored by his peers, Professor Washino received the international Harry Hoogstraal Medal for Outstanding Achievement in Medical Entomology in 2005 and was selected a fellow of the Entomological Society of America in 1997. Among his many other awards: the  2001 Award of Distinction from the UC Davis College of Agricultural and Environmental Sciences and the 1996 Distinguished Achievement Award from the Society of Vector Ecology. At the 2001 Award of Distinction celebration on Oct. 19, 2001, Andrew Spielman, professor of tropical public health, Harvard School of Public Health, praised him this way: “I regard Bob as the most respected and best loved medical entomologist in the whole world." 

Robert Washino is also a veteran.

A veteran of the U.S. Army Medical Service Corps.

And today is Veterans' Day.

It's time, past time, to say "Thank you, Dr. Washino, for your service."

Steve Seybold specialized in the chemical ecology of forest insects.

• "A Study of Landing Behaviour by the Walnut Twig Beetle, Pityophthorus juglandis, Among Host and Nonhost Hardwood Trees in a Northern California Riparian Forest" (https://doi.org/10.1111/afe.12385). 
• "Walnut Twig Beetle Landing Rates Differ Between Host and Nonhost Hardwood Trees under the Influence of Aggregation Pheromone in a Northern California Riparian Forest" (https://doi.org/10.1111/afe.12410)

The walnut twig beetle, in association with the fungus, Geosmithia morbida, causes the insect-pathogen complex known as "thousand cankers disease," which wreaks havoc on walnut trees. The insect, measuring about 1.5 millimeters long, is smaller than a grain of rice.

"The first study is one of few bark beetle host selection studies conducted without the use of semiochemical lures," Audley said. "Together, both studies provide strong evidence for directed flight host searching and in-flight, host discrimination behaviors by Pityophthorus juglandis. These papers highlight sources of and provide an ecological context for potential non-host, volatile compounds that may be of use in semiochemical repellents to protect walnut trees from attack by P. juglandis." 

Jackson Audley, co-author

"Steve was a giant in the forest entomology community, particularly in the field of bark beetle chemical ecology," Audley said. "He was a great mentor and I am fairly confident I would not be half the scientist I am today without his guidance."

SaidHomicz: "Our papers highlight that the walnut twig beetle is highly skilled at discerning hosts in flight. Even when we attempt to lure them to non-host trees by tricking them with aggregation pheromone, more often than not, they correctly identify their host tree. This shows the beetle has evolved to be highly tuned into its  environment and the volatile profiles of its host species. Yet another example of how complex and advanced the insect olfactory system is! Future work may focus on identifying repellent chemical compounds released by the non-host tree species included in our studies." 

Crystal Homicz, co-author

"Not only was Steve a giant in the forest entomology community, but he was a giant in my life," Homicz commented. "I would not be studying forest entomology if not for him, and I am incredibly grateful he introduced me to my life's passion. Steve was highly committed to investing time and energy into young scientists. He was also committed to community outreach, I know he shared his love of trees and insects with many people!"

Seybold, who died Nov. 15, 2019 of a heart condition, was a researcher at the Pacific Southwest Research Station, USDA Forest Service, Davis, where he specialized in the chemical ecology of forest insects. He was also a lecturer and researcher with the UC Davis Department of Entomology and Nematology and mentored students. 

Richard Bostock, distinguished professor, UC Davis Department of Plant Pathology, served as a co-author on both papers (in addition to Audley, Homicz and Seybold).

First Paper: A Study of Landing Behavior 

The abstract:

• The host selection behaviour of the walnut twig beetle, Pityophthorus juglandis, was assessed by monitoring the landing rates of the beetles with sticky sheet traps on the host and nonhost hardwood branches.
• Sticky sheet traps were deployed for 8 weeks from 6 June to 2 August. 2017 in the Putah Creek Riparian Reserve, Davis, CA. Branches from host northern California black walnut, Juglans hindsii, were paired with branches from six nonhost hardwood species.
• The landing rate of P. juglandis (412 beetles trapped/8 weeks; 389 on host branches, 23 on nonhost branches) was significantly greater on the host branches for all nonhost hardwoods except Populus fremontii. Proportional comparisons of beetle presence also revealed a significant preference for the host branches compared with all but two nonhost species, Acer negundo and P. fremontii.
• Capturing P. juglandis without the use of an aggregation pheromone was a rare event, underscoring the difficulty of studying the initial phases of host selection behaviour in bark beetles. Unbaited funnel traps adjacent to selected host trees in the experiment only captured five individuals over a 19‐week period. None were captured in traps adjacent to nonhost trees.
• This study provided evidence that P. juglandis discriminates between host and nonhost branches while in‐flight. This directed flight behaviour is likely informed by the recognition of both host and nonhost volatile cues.
• This study established an ecological context for the development of a semiochemical‐based repellent system for protecting walnut trees from future attacks from this invasive bark beetle. 

Second Paper: Walnut Twig Beetle Landing Rates

The abstract:

1. Host selection behaviour of the walnut twig beetle (WTB) among hardwood trees was investigated in a riparian forest in northern California by monitoring the landing rate of the beetle with sticky traps on branches baited with 3‐methyl‐2‐buten‐1‐ol, the male‐produced aggregation pheromone.
2. The assay was conducted over 7 days (22 May to 29 May 2017) and compared landing rates on branches of six nonhost species paired with northern California black walnut, Juglans hindsii (the host).
3. A total of 2242/1192 WTB were collected on branches of host/nonhost pairs, and more WTB landed on J. hindsii than on nonhosts in 42 of 58 instances. Female landing rate generally exceeded male landing rate, which underscores the influence of the male‐produced synthetic pheromone in this system.
4. Landing rates of WTB males, females, and the combined sexes on boxelder, Acer negundo, and valley oak, Quercus lobata, did not differ significantly from the landing rates on J. hindsii, suggesting that these two nonhost riparian hardwoods do not repel WTB (in the context of the aggregation pheromone).
5. Significantly fewer WTB landed on Oregon ash, Fraxinus latifolia, river red gum, Eucalyptus camaldulensis, Fremont cottonwood, Populus fremontii, and red willow, Salix laevigata, than on J. hindsii, which suggests that these four nonhosts may repel one or both sexes of WTB in the context of the aggregation pheromone. Future analysis of the volatiles from these four hardwood species may lead to the discovery of semiochemical repellents for WTB.

Co-authors (in addition to Audley, Homicz, Seybold and Bostock) are Yigen Chen, Foundation Research, Analytics and Business Applications, E. & J. Gallo Winery, Modesto, Calif.; and scientist Catherine Tauber, UC Davis Department of Entomology and Nematology, and formerly with the Department of Entomology, Cornell University, Ithaca, N.Y.

Jackson Audley

Audley is now a postdoctoral fellow funded by the Oak Ridge Laboratories, and based at the USDA Forest Service, Pacific Southwest Research Station, Davis.  While at UC Davis, Audley investigated behavioral chemicals that repel the walnut twig beetle from landing on English walnut trees. He conducted his research in a commercial orchard near Winters. He received the 2019 Western Forest Insect Work Conference (WFIWC) Memorial Scholarship Award for his research on the chemical ecology of the walnut twig beetle. He holds a master's degree in forestry (2015) from the University of Tennessee, and a bachelor of science degree in wildlife biology and natural resource recreation and tourism (2009) from the University of Georgia. 

Crystal Homicz

Homicz, who joined the UC Davis doctoral program in September 2019, received a bachelor of science degree in animal biology with an emphasis in entomology (2018) from UC Davis. Her practicum: "Landing Behavior of the Walnut Twig Beetle on Host and Non-Host Hardwood Trees Under the Influence of Aggregation Pheromone in a Northern California Riparian Forest."  She holds associate degrees in both biology and natural sciences (2016) from Shasta College.

For more information on the walnut twig beetle and thousand cankers disease, see the UC Statewide Integrated Pest Management Program website.

A blue orchard bee at its nesting site on the grounds of the Harry H. Laidlaw Jr. Honey Bee Research Facility in the spring of 2018. (Photo by Kathy Keatley Garvey)

Lead author and doctoral student Clara Stuligross teamed with her major professor, pollination ecologist Neal Williams of the UC Davis Department of Entomology and Nematology, to publish Pesticide and Resource Stressors Additively Impair Wild Bee Reproduction, in the journal Proceedings of the Royal Society B. 

They exposed the bees to the neonicotinoid insecticide imidacloprid, widely used in agriculture, and found that the combined threats—imidacloprid exposure and the loss of flowering plants—reduced the bee's reproduction by 57 percent, resulting in fewer female offspring. 

Of the two stressors—food scarcity and pesticide exposure—pesticide exposure showed the great impact on nesting activity and the number of offspring produced, they said. 

Other scientists have conducted similar research on honey bees, but this is the first comparable research on wild bees in field or semi-field conditions. 

The blue orchard bee, nicknamed BOB, is a dark metallic mason bee, smaller than a honey bee. It is prized for pollinating almond, apple, plum, pear, and peach trees. California almond growers often set up bee boxes or "bee condos" for blue orchard bees to aid in honey bee pollination. In the wild, the bees nest in reeds or natural holes. 

“Bees and other beneficial insects experience multiple stressors within agricultural landscapes that act together to impact their health and diminish their ability to deliver the ecosystem services on which human food supplies depend,” Stuligross and Williams wrote in their abstract. “Disentangling the effects of coupled stressors is a primary challenge for understanding how to promote their populations and ensure robust pollination and other ecosystem services.” 

To study the survival, nesting and reproduction of the blue orchard bee, they set up nesting females in large flight cages, some with high densities of wildflowers and others with low densities that were treated “with or without the common insecticide, imidacloprid.” Bees are commonly exposed to insecticides when they forage on treated flowers. 

“Pesticides and resource limitation acted additively to dramatically reduce reproduction in free-flying bees,” they wrote in their abstract. “Our results emphasize the importance of considering multiple drivers to inform population persistence, management, and risk assessment for the long-term sustainability of food production and natural ecosystems.” 

UC Davis doctoral student Clara Stuligross

Key factors in affecting bee reproduction are the probability that females will nest and the total number of offspring they have. The UC Davis research found that pesticide-exposed and resource-deprived female bees delayed the onset of nesting by 3.6 days and spent five fewer days nesting than unexposed bees.

Professor Neal Williams, pollination ecologist (Photo by Kathy Keatley Garvey)

They found that only 62 percent of pesticide-exposed bees produced at least one daughter compared to 92 percent of bees not exposed to pesticides.

The research, accomplished in the spring of 2018 on the grounds of the Harry H. Laidlaw Jr. Facility west of the campus,  drew support from a UC Davis Jastro Research Award, a UC Davis Ecology Graduate Research Fellowship, a National Science Foundation Graduate Research Fellowship, and the UC Davis bee biology facility

The blue orchard bee bee is one of the few native pollinators that is managed in agriculture. North America has 140 species of Osmia, according to a Pollinator Partnership (PP) article in a U. S. Forest Service publication, authored by entomologist and PP member Beatriz Moisset and PP director Vicki Wojcik. “Mason bees use clay to make partitions and to seal the entrance,” they wrote. “This unique mud-building behavior leads to their common designation as mason bees. Honey bees are very important to commercial agriculture, but native bees like the blue orchard bees are better and more efficient pollinators of native crops.”

Imidacloprid, a systemic insecticide that acts as an insect neurotoxin, is used to control sucking insects, termites, some soil insects and fleas on pets, according to National Pesticide Information Center. It mimics nicotine, toxic to insects, which is naturally found in many plants, including tobacco.  More than 400 products for sale in the United States contain imidacloprid.