Robbin Thorp is concerned about Franklin's bumble bee, which he fears may be extinct. (Photo by Kathy Keatley Garvey)

When the 103rd annual meeting of the Pacific Branch of the Entomological Society of America (PBESA) takes place March 31-April 3 in the Hyatt Regency Mission Bay Spa and Marina, San Diego, something very special will happen.

Native pollinator specialist Robbin Thorp, UC Davis distinguished emeritus professor of entomology and a global authority on bumble bees and other native pollinators, will be honored at a special symposium being planned by his colleague, pollination ecologist Neal Williams, professor, UC Davis Department of Entomology and Nematology.

The event is set for Tuesday afternoon, April 2.

“The symposium will include scientific contributions from leaders in the fields of bee ecology, conservation and pollination,” announced Williams. “All are individuals whose work and specialty have  been influenced by Robbin and his research program."

The scientists speaking include:

• Neal Williams, UC Davis
• Claire Kremen, University of British Columbia, formerly of UC Berkeley
• James Strange, USDA's Agricultural Research Service
• Heidi Dobson, Whitman College, Walla Walla, Wash.
• Gretchen Lebuhn, San Francisco State University
• Richard Hatfield, Xerces Society for Invertebrate Conservation
• Terry Griswold, USDA's Agricultural Research Service
• Leslie Saul-Gershenz, UC Davis
• Gordon Frankie, UC Berkeley

This is Franklin's bumble bee, which is feared extinct. (Photo by Robbin Thorp)

Thorp, a member of the UC Davis entomology faculty for 30 years, from 1964-1994, achieved emeritus status in 1994 but has continued to engage in research, teaching and public service.  In his retirement, he co-authored two books Bumble Bees of North America, an Identification Guide (Princeton University, 2014) and California Bees and Blooms, A Guide for Gardeners and Naturalists (Heyday, 2014).

Thorp, a tireless advocate of pollinator species protection and conservation, is known for his expertise, dedication and passion in protecting native pollinators, especially bumble bees, and for his teaching, research and public service. He is an authority on pollination ecology, ecology and systematics of honey bees, bumble bees, vernal pool bees, conservation of bees, contribution of native bees to crop pollination, and bees of urban gardens and agricultural landscapes. He is active in research projects and open houses at the Bohart Museum of Entomology.

Thorp received his bachelor of science degree in zoology (1955) and his master's degree in zoology (1957) from the University of Michigan, Ann Arbor. He earned his doctorate in entomology in 1964 from UC Berkeley, the same year he joined the UC Davis entomology faculty. He taught courses from 1970 to 2006 on insect classification, general entomology, natural history of insects, field entomology, California insect diversity, and pollination ecology. 

Every summer since 2002, Thorp has volunteered his time and expertise to teach at The Bee Course, an annual workshop sponsored by the American Museum of Natural History and held at the Southwestern Research Station, Portal, Ariz. The intensive 9-day workshop, considered the world's premiere native bee biology and taxonomic course, is geared for conservation biologists, pollination ecologists and other biologists who want to gain greater knowledge of the systematics and biology of bees. 

An authority on Franklin's bumble bee, Bombus franklini, Thorp has monitored the bumble bee population since 1998 in its narrow distribution range of southern Oregon and northern California. He has not seen it since 2006 and it is feared extinct. In August of 2016 a documentary crew from CNN, headed by John Sutter followed him to a meadow where Thorp last saw Franklin's bumble bee. He wrote about Thorp, then 82, in a piece he called "The Old Man and the Bee," a spinoff of Ernest Hemingway's "The Old Man and the Sea." 

Thorp was instrumental in placing the bumble bee on the Red List of Threatened Species of the International Union for Conservation of Nature and Natural Resources (IUCN). Long active in the North America IUCN Bumblebee Specialist Group, Thorp served as its regional co-chair, beginning in 2011.

Thorp was named a fellow of the California Academy of Sciences, San Francisco in 1986; recipient of the  Edward A. Dickson Emeriti Professorship of UC Davis in 2010; and recipient of the UC Davis Distinguished Emeritus Award in 2015. Other honors include: member of the UC Davis Bee Team that won PBESA's Team Award in 2013.  In addition, he is a past president (2010-2011) of the Davis Botanical Society, and former chair (1992-2011) of the Advisory Committee for the Jepson Prairie Reserve, UC Davis/Natural Reserve System.

Since its inception, Thorp has been involved in the Häagen-Dazs Honey Bee Haven, a half-acre bee garden on Bee Biology Road operated by the UC Davis Department of Entomology and Nematology, installed in 2009. To establish a baseline, he began monitoring the site for bees in 2008. He has since detected more than 80 species of bees.

Thorp has identified thousands and thousands of native bees for scientists, citizen scientists, and the general public, in addition to his other work involving research, teaching, mentoring and public service.

And now he will be honored at a special PBESA symposium.   PBESA encompasses 11 Western U.S. states, plus several U.S. territories and parts of Canada and Mexico.

It's an honor well deserved.

Laura Burke, associate professor, Montana State University, studies insect-plant interactions.

But more about that later.

Community ecologist Laura Burkle, associate professor in the Department of Ecology, Montana State University, Bozeman, is keenly interested in plant-insect interactions, especially floral volatile organic compounds (VOCs).

She'll discuss her research on “The Implications of Variation in Floral Volatiles for Plant-Pollinator Interactions" at the UC Davis Department of Entomology and Nematology seminar from 4:10 to 5 p.m., Wednesday, Jan. 30 in 122 Briggs Hall, UC Davis campus. Hosts are pollination ecologist Neal Williams, professor in the UC Davis Department of Entomology and Nematology, and doctoral student Maureen Page of the Williams lab.

“One understudied pathway by which environmental conditions and climate change may influence plant-pollinator interactions is via shifts in floral scent and pollinator attraction,” Burkle says in her abstract. “We sampled the floral volatile organic compounds (VOCs), phenologies, and pollinator visitors from naturally growing plants in a montane meadow over three seasons. With these data, we aim to acquire a base understanding of the variation in floral VOCs within and among species and how floral VOCs and other plant traits may structure plant-pollinator interactions across the growing season and across years.”

How did Burkle interested in bees and pollination? “At the Rocky Mountain Biological Lab in Colorado,” she says.

“To be honest, in college I was enamored with marine biology, until I realized that I didn't like being continuously wet while doing field work. Plants I liked because they stayed put for observation (unless eaten by a deer or something)...my interest in bees followed later.  Bees and pollination are great fair-weather friends, literally :) And I'm fascinated by the complexity of their interactions with each other.”

Burkle received her bachelor of science degree in biology and environmental studies in 2000 from Bowdoin College, Brunswick, Maine, and then headed to Hanover, N.H., for her doctorate in biology in Dartmouth College's Ecology and Evolution program. Her dissertation: “Bottom-up Effects of Nutrient Enrichment on Plants, Pollinators and Their Interactions.”

Burkle served as a postdoctoral research associate in the Department of Biology at Washington University, St. Louis, from 2008 to 2010, and then joined the Department of Ecology at Montana State University as an assistant professor in 2011. She advanced to associate professor in 2017. At Montana State University, Burkle has taught Principles of Biological Diversity, Plant Ecology, Community Ecology, Ecological Networks and Disturbance Ecology.

She has published her work in Plant Ecology, New Phytologist, Biological Reviews, and Nature Ecology and Evolution, among others. She was the lead author of the technical publication, "Climate Change and Range Shifts" in the North American Bumble Bee Species Conservation Planning Workshop Final Report, published in 2011.

Her 2019 publications include “Checklist of Bees (Hymenoptera: Apoidea) from Small Diversified Vegetable Farms in Southwestern Montana” in the Biodiversity Data Journal; “Dryland Organic Farming Increases Floral Resources and Bee Colony Success in Highly Simplified Agricultural Landscapes” in Agriculture, Ecosystems and Environment; and “The Effects of Post-Wildlife Logging on Plant Reproductive Success and Pollination in Symphoricarpos albus,” a fire-tolerant shrub, published in Forest Ecology and Management.

Jenita Thinakaran, UC Davis postdoctoral researcher

But you should be.

You should especially be thinking about the zebra chip. No, it's not a newly marketed potato chip or computer chip.

Basically, it's a disease of potatoes transmitted by the potato psyllid. It's caused by the bacterium Candidatus Liberibacter solanacearum.

The disease, first identified in 1994 near Saltillo, Mexico, causes major economic damage and is spreading throughout much of the United States, including Arizona, California, Colorado, Idaho, Oregon, Kansas, Nebraska and New Mexico.

"When fried, potato tubers from infected plants develop unsightly black lines resembling the stripes of zebras that render the chips unsellable," according to Wikipedia. "Additionally, striped sections of chips frequently burn and caramelize, resulting in a bitter flavor. No health risks have been connected with consumption of infected potato chips."

The Yakima (Wash.) Herald spotlighted zebra chip in a May 2015 news story featuring Rodney Cooper, a research entomologist with the USDA's Agricultural Research Service laboratory in Wapato, Wash., and Jenita Thinakaran, then a postdoctoral research associate at the laboratory.

And now, Thinakaran,  a UC Davis postdoctoral researcher based at the Shafter (Calif.) Agricultural Research Station, will present a UC Davis Department of Entomology and Nematology seminar on "A Systems Approach to Managing Potato Psyllid in Relation to Its Alternate Hosts" at 4:10 p.m., Wednesday, Jan. 23 in 122 Briggs Hall.

In his news story, Yakima-Herald reporter Ross Courtney described the disease as "a brown, streaky condition inside the flesh of the tubers most noticeable after they've been sliced and fried, such as for potato chips."

Researchers don't believe the infected potatoes pose any health threat, but farmers know customers won't buy them, Courtney related. "Research is underway, but the stakes could be high. The disease shows up in several countries around the world. In New Zealand, zebra chip cost growers $22.5 million in 2010 and 2011, according to a 2012 paper by Joseph Munyaneza, a Wapato laboratory colleague of the two researchers. In northern Mexico, zebra chip has been known to wipe out 60 percent of the crop, forcing farmers to abandon entire fields. Tomato and pepper farmers throughout the world have noticed crop losses due to the same bacteria."

What about potato psyllids in California?

"Psyllids used to be an occasional problem in California in certain years when they would migrate into the state from Mexico,"  according to the UC Statewide Integrated Pest Management Program (UC IPM) website. "In recent years, however, a more invasive form of the species has been found in California that has the ability to overwinter in parts of southern California. Potato psyllid now occurs on a yearly basis in these areas and has become a chronic problem."

UC IPM describes the pest as looking like a "small cicada, about 0.08 inch (2 mm) long" and related to aphids and leafhoppers. "The adult has clear wings that rest rooflike over the body," UC IPM says. "Although predominantly black, the potato psyllid does possess white markings. The first abdominal segment shows a broad white band, the last segment has an inverted white 'V.' Psyllids jump quite readily when disturbed."

"The football-shaped eggs are extremely small, slightly larger than leaf hairs, and on a short stalk. They are usually on the underside of the leaf along the edge and in the upper plant canopy. A 10X hand lens is required to see them."

Thinakaran, who holds a doctorate in horticulture from Texas A&M University, College Station, completed her dissertation in 2014 on "Evaluation of Potato Psyllid, Bactericera cockerelli (suic) (Hemiptera: Triozidae), Host Preferences, Adaptation, Behavior and Transmission of 'Candidatus Liberibacter solanacearum' among Wild and Cultivated Solanaceous Hosts in the Lower Rio Grande Valley of Texas." She studied with major professors Don Henne and Elizabeth Pierson.

At her UC Davis seminar, Thinakaran will discuss the economic damage of the pest, its hosts, and her ongoing research. "The research I will be presenting relates to my previous work at Texas A&M and USDA-ARS. Dr. Don Henne (presently with Lakehead University, Canada), Drs. Joseph Munyaneza, Rodney Cooper and David Horton with USDA-ARS and Dr. Andy Jensen (Northwest Potato Research Consortium)," she relates.

The potato psyllid "causes economic damage to potato crops throughout the major potato growing regions along the Rocky mountain corridor," she writes in her abstract. "Settling and oviposition preferences were studied on its wild and cultivated solanaceous hosts, including potato, tomato, pepper, eggplant, and silverleaf nightshade (SLN). Silverleaf nightshade is a common weed in the Lower Rio Grande Valley of Texas and a host for both the potato psyllid and Lso pathogen. Results of settling and oviposition studies indicated that potato psyllid preferred potato and tomato equally for settling and oviposition, but settled on pepper, eggplant, and SLN. Transmission studies determined that potato psyllid can acquire Lso within a 2-week acquisition period on Lso-infected SLN and can serve as a reservoir for Lso, providing a source of inoculum for potato psyllid adults colonizing potato during the following season. Under laboratory conditions, potato psyllid preferred larger host plants, regardless of the species tested. Lone plants attracted the most psyllids and can be used as sentinel plants to monitor potato psyllid activity. When cultivated crops are not available, potato psyllid often occurs on non-crop hosts.

"To test the hypothesis that potato psyllid are year-round residents, not migrants from more southern regions, monitoring of Lycium spp. was undertaken in the Pacific Northwest (PNW) throughout the year from June 2014 to June 2016," Thinakaran relates. "Lycium in the PNW occurs as two different species and collectively referred as matrimony vine and Goji berry. Not knowing the source of psyllids makes it difficult to predict when and in what fields the psyllids will arrive. Our monitoring results provide circumstantial evidence that matrimony vine is a source of potato psyllid arriving in potato fields of the PNW. All 14 stands of matrimony vine that were examined in Washington, Idaho and Oregon were found to be infested with potato psyllid suggesting that association of potato psyllid with matrimony vine in the PNW is common and widespread and that matrimony vine is also a host when the potato crop is seasonally not available."

Thinakaran points out that "psyllids began showing up in potato fields at virtually the same time that they were disappearing from matrimony vine, coinciding with the onset of summer defoliation. Indeed, psyllid numbers on matrimony vine in the spring may be found to accurately predict the numbers of psyllids that eventually migrate into potato. Ongoing research in 2018 and beyond will reveal whether matrimony vine can be used by growers as an early warning system to predict the risk of potato psyllids colonizing potato fields."

Thinakaran received three degrees in India: her bachelor of science degree in agriculture and her master's degree in agricultural entomology, both from TamilNadu Agricultural University in Coimbatore, and her master of business administration (MBA) in operations management from Indira Gandhi National Open University in New Delhi. She owned and operated an agro business in Coimbatore until her career took her to TamilNadu as a senior research fellow and then to Texas A&M for her doctoral studies.

The UC Davis Department of Entomology and Nematology seminars, coordinated by medical entomologist Geoffrey Attardo, assistant professor, are held every Wednesday at 4:10 p.m. in Briggs Hall. (See schedule.)

Rick Karban, professor, UC Davis Department of Entomology and Nematology

A recent article in Science headlined "Once Considered Outlandish, the Idea that Plants Help their Relatives Is Taking Root," and dealing with how plants communicate, is drawing widespread attention.

Wrote Elizabeth Pennisi: "For people, and many other animals, family matters. Consider how many jobs go to relatives. Or how an ant will ruthlessly attack intruder ants but rescue injured, closely related nestmates. There are good evolutionary reasons to aid relatives, after all. Now, it seems, family feelings may stir in plants as well."

"A Canadian biologist planted the seed of the idea more than a decade ago, but many plant biologists regarded it as heretical—plants lack the nervous systems that enable animals to recognize kin, so how can they know their relatives? But with a series of recent findings, the notion that plants really do care for their most genetically close peers—in a quiet, plant-y way—is taking root. Some species constrain how far their roots spread, others change how many flowers they produce, and a few tilt or shift their leaves to minimize shading of neighboring plants, favoring related individuals."

Pennisi quoted ecologist Richard "Rick" Karban, professor in the UC Davis Department of Entomology and Nematology, for her piece. An international authority on plant communication, he authored the 240-page book, Plant Sensing and Communication (University of Chicago Press), considered a landmark in its field.

An excerpt from Science: "Sagebrush bushes (Artemisia tridentata) have provided some strong clues, however. When injured by herbivores, these plants release volatile chemicals that stimulate neighboring sagebrush to make chemicals toxic to their shared enemies. Ecologist Richard Karban at the University of California, Davis, wondered whether kin were preferentially warned. His group had already found that sagebrush plants roughly fall into two "chemotypes," which mainly emit either camphor or another organic compound called thujone when their leaves are damaged. The team showed that the chemotypes are heritable, making them a potential kin recognition signal. In 2014, the researchers reported that when volatiles from a plant of one chemotype were applied to the same type of plant, those plants mounted stronger antiherbivore defenses and had much less insect damage than when the volatiles were applied to a plant of the other chemotype—a hint of a kin effect."

She concluded with a quote from Karban: "We are learning that plants are capable of so much more sophisticated behavior than we had thought. It's really cool stuff." 

Update?

"We aren't actually doing more work that addresses the issue of kin recognition," Karban told us. "We have found that sagebrush plants communicate more effectively with kin than strangers and more effectively with other individuals that belong to the same 'chemotype' as they do.  Chemotypes are similar to blood types - they represent chemical variation among individuals in the population. As with blood types, it is puzzling why this variation exists.  The cues that sagebrush use to communicate are potentially extremely complex; we can identify on the order of 100 volatile compounds that are emitted by damaged foliage.  This gives an enormous number of possible 'words' that could provide information in the 'language' that the plants may be using.  Since the chemotypes differ in only a few compounds, we are hoping that focusing on chemotypic variation will provide some clues that help us begin to decipher the language of the plants.

Karban has researched plant communication in Artemisia tridentataon the east side of the Sierra since 1995. His groundbreaking research on plant communication among kin, published in February 2013 in the Proceedings of the Royal Society B: Biological Sciences, drew international attention. In that study, Karban and his co-researchers found that kin have distinct advantages when it comes to plant communication, just as “the ability of many animals to recognize kin has allowed them to evolve diverse cooperative behaviors.” 

“Plants responded more effectively to volatile cues from close relatives than from distant relatives in all four experiments and communication reduced levels of leaf damage experienced over the three growing seasons,” Karban wrote.

The gist of it: if you're a sagebrush and a predator (such as a grasshopper) is eating your nearby kin, another sagebrush,  it's good to be closely related. Through volatile (chemical) cues, your kin will inform you of the danger so you can adjust your defenses. Yes, plants can communicate.

We remember asking Karban several years go "the 10 things to know about plant sensing and communication." According to Karban:

1. Plants sense their environments and respond.
2. Although they lack central nervous systems, they process information and appear to "behave intelligently."
3. They sense the position of competitors and "forage" for light.
4. They sense the availability of water and nutrients in the soil and "forage" for these resources.
5. Their decisions are influenced by past experiences, akin to memory.
6. They respond to reliable cues that predict future events, allowing them to "anticipate."
7. Plants respond differently to cues that they themselves produce, allowing them to distinguish self from non-self.
8. They respond differently to close relatives and strangers.
9. Plants that are prevented from sensing or responding experience reduced fitness.
10. By understanding the "language" of plant responses, we can grow healthier and more productive plants.

The most basic form of communication? When a plant is being shaded, it senses the diminished light quality caused by a competitor and responds by moving away, Karban says.

Karban's work on plant communication is featured in a 2016 interactive lesson plan, TED-Ed Original Lessons where "words and ideas of educators are brought to life by professional animators.” Plants can eavesdrop, sense danger in the environment, and can distinguish friend from foe, he says.