Urban landscape entomologist Emily Meineke (Photo by Leon Godwin)

“However, the plants that are keeping up with climate change might also experience costs to earlier leaf-out,” said Meineke, lead author of the first-of-its-kind study, Phenological Sensitivity to Temperature Mediates Herbivory. 

One of the costs is that “early” species get eaten more in warmer years. “This seems to be because when they leaf out earlier,” she said, “they also lengthen the amount of time herbivores have in a given year to eat their leaves.” 

Two plant species that showed higher insect damage due to rising temperatures were two native blueberries: Vaccinium angustifolium, a wild lowbush blueberry native to eastern and central Canada and the northeastern United States, and Vaccinium corymbosum, the northern highbush blueberry, a native North American species and a significant commercial food crop. 

The publication is the result of a massive five-year research project involving herbarium specimens collected from the northeastern United States and France from 1900 to 2015.  These two areas have warmed more than the global average, Meineke said, and the plants studied are distributed widely across them.

Meineke, an assistant professor who joined the UC Davis faculty in March 2020, launched her research while a National Science Foundation postdoctoral fellow at the Harvard University Herbaria, where she studied how worldwide urbanization and climate change have affected plant-insect relationships over the past century.

The blueberry, Vaccinium corymbosum, is a significant commercial food crop. (Photo by Kathy Keatley Garvey)

“This was a true collaboration,” Meineke said. “Each of us was interested in different pieces of the research. Davies and Davis brought the phenology hypotheses and expertise, and I brought an interest in/knowledge of herbivory and how it may change as the climate warms.” 

The authors wrote that “both insect and plant development are sensitive to temperature, though the specific cues plants and associated insects use to time life history events may differ and include photoperiod, chilling, ‘forcing' and precipitation. For the vast majority of insect and plant species, the combined and relative contributions of these cues have not been well characterized.” 

The specimens studied were selected first on the basis of the availability of previously published phenological sensitivity metrics: flowering sensitivity and leaf-out sensitivity. “We use the general term ‘phenological sensitivity' to refer to the extent to which a particular life event (e.g., for plants, budbreak, leaf-out, flowering, fruiting) responds to temperature from year to year (e.g. days change in phenology per ‘C' warming),” they explained. 

The next step? “We are now beginning to look into whether and how herbivory might have shifted over time in California native plants,” Meineke said. “Our focal species so far is the valley oak, Quercus lobata, but we hope to eventually expand these observations to more taxa. We're also looking into other mechanisms that might drive herbivory shifts here in the west, where phenology is driven more by moisture than by temperature.” 

A native of Greenville, N.C., Meineke holds a bachelor's degree from the University of North Carolina in environmental science, with a minor in biology, and a doctorate in entomology from North Carolina State University where she completed her dissertation,  "Understanding the Consequences of Urban Warming for Street Trees and Their Insect Pests.” 

The project was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada. The material is based upon work supported by the National Science Foundation Postdoctoral Research Fellowship in Biology in a grant awarded to Meineke. 

The abstract:

Species interactions drive ecosystem processes and are a major focus of global change research. Among the most consequential interactions expected to shift with climate change are those between insect herbivores and plants, both of which are highly sensitive to temperature. Insect herbivores and their host plants display varying levels of synchrony that could be disrupted or enhanced by climate change, yet empirical data on changes in synchrony are lacking. Using evidence of herbivory on herbarium specimens collected from the northeastern United States and France from 1900 to 2015, we provide evidence that plant species with temperature‐sensitive phenologies experience higher levels of insect damage in warmer years, while less temperature‐sensitive, co‐occurring species do not. While herbivory might be mediated by interactions between warming and phenology through multiple pathways, we suggest that warming might lengthen growing seasons for phenologically sensitive plant species, exposing their leaves to herbivores for longer periods of time in warm years. We propose that elevated herbivory in warm years may represent a previously under appreciated cost to phenological tracking of climate change over longer timescales.  

Ian Grettenberger, coordinator

All seminars will be held on Wednesdays at 4:10 p.m. (Pacific). Join the Zoom seminars by accessing the links below.

March 31 
Bob Peterson 
Montana State University, Land Resources and Environmental Sciences
Title: "Tigers in Yellowstone National Park: Insect Adaptations to Extreme Environments" 
Host: James R. Carey
See seminar at https://youtu.be/z85B0NlmizU

April 14
Swapna Priya Rajarapu
North Carolina State University, Department of Entomology and Plant Pathology
Title: "Insect-Plant Molecular Interactions: Stories from Invasive Insects to Disease Vectors"
Host: Diane Ullman
Zoom info

April 21 
Chris Hamilton
University of Idaho, Department of Entomology, Plant Pathology and Nematology
Title: "Understanding Aphonopelma Diversity Across the Madrean Pine-Oak Woodlands Hotspot by Integrating Western Science and Traditional Ecological Knowledge (TEK)"
Host: Jason Bond
Zoom info

April 28
Ellen Currano
University of Wyoming, Department of Geology and Geophysics
Title: "Ancient Bug-Bitten Leaves Reveal the Impacts of Climate and Plant Nutrients on Insect Herbivores"
Host: Emily Meineke
Zoom info

May 5 
Gabe Zilnik
USDA-ARS Wapato, Wash., Temperate Tree Fruit and Vegetable Research
Title: "Improving Tobacco IPM with Machine Learning"
Host: Madi Hendrick
Zoom info

May 12
Margarita López-Uribe
Pennsylvania State University, Department of Entomology
Title: "Ecoevolutionary Consequences of Crop Domestication on Plant-Pollinator Interactions"
Host: Rachel Vannette
Zoom info

May 19
Manuela Ramalho 
Cornell University
Title: "Exploring Connections Among Microbial Community, Ecology and Phylogenetic History of Ants" 
Host: Marshal McMunn
Zoom info

May 26
Javier Ceja Navarro
Lawrence Berkeley National Laboratory, Biological Systems and Engineering 
Title:  (Pending) 
Host: Rachel Vannette 
Zoom info

June 2 
Alexandra Harmon-Threatt
University of Illinois Urbana-Champaign, Department of Entomology 
Title: (Pending) 
Host: Neal Williams 
Zoom info

For any questions, email Ian Grettenberger (imgrettenberger@ucdavis.edu).

Swapna Priya Rajarapu

Insect physiologist Swapna Priya Rajarapu, a postdoctoral research scholar in the Dorith Rotenberg laboratory at North Carolina State University, Raleigh, will present the next seminar hosted by the UC Davis Department of Entomology and Nematology.

A first-generation college student, Rajarapu holds two biochemistry degrees from Osmania University, India: her bachelor's degree (2006) and her master's degree (2008). She obtained her doctorate in entomology in 2013 from The Ohio State University, working with Professors Daniel Herms and Larry Phelan. Her dissertation: "Integrated Omics on the Physiology of Emerald Ash Borer."

Andrew Sutherland in the Urban Pest Management Laboratory at UC Berkeley’s Richmond Field Station. (Cell phone image by Andrew Sutherland)

Sutherland, UC Riverside professor and urban entomologist Chow-Yang Lee, and USDA forest entomologist Lori Nelson want to compare the spring swarming populations of Reticulitermes hesperus with the fall swarming populations.

“A major taxonomic question surrounding western subterranean termites remains unsolved,” said Sutherland, the Urban IPM Advisor for the San Francisco Bay Area.  “Most termite species simultaneously swarm over a relatively short period during one season, facilitating genetic exchange during mating. Individuals thought to represent Reticulitermes hesperus, however, have been observed swarming during both autumn (usually on a sunny day after the first autumn rain event) and spring (sunny days when soil is moist) suggesting that there are at least two cryptic species considered within the western subterranean termite complex or that speciation is underway (individuals swarming at different times of the year cannot mate with one another).”

In fact, says Sutherland, USDA Forest Service research by Michael Haverty and Lori Nelson indicates that spring and autumn swarming populations can actually be distinguished by different cuticular hydrocarbons (waxes on exoskeleton).

In the collaborative UC IPM, UC Riverside, and USDA Forest Service research project, “we seek to resolve this question once and for all by comparing DNA microsatellite data and cuticular hydrocarbon data from alates (winged termite swarmers) collected during these different seasons,” Sutherland said.

Residents of California, Oregon, Washington, Idaho, western Nevada, southern British Columbia, and northern Baja California can help by collecting at least 25 individuals of swarming Reticulitermes and freezing them in a hard-walled container, such as a pill bottle, film canister or a food storage plastic container. Contributors will receive a Common Cockroaches of California poster or another special gift. Contributing pest management professionals will receive a free training opportunity with ‘IPM' continuing education units for California's Structural Pest Control Board licenses.

Sutherland's program will fund the shipping of the specimens. He may be reached at amsutherland@ucanr.edu for further information, such as if the termite specimens qualify.

About Termites and Sutherland's Work
Termites, like cockroaches, are members of the order Blattodea and evolved some 120 million years ago. Structural infestations of subterranean termites are usually not visible, but the annual flights of winged termites (alates) are. This research will help pest control providers and residents understand the most likely swarming periods in their specific region, improving monitoring and control for these important structural pests.

Sutherland, who began researching termites in 2014, says the western subterranean termite, “is the most damaging wood destroying insect in northern California and most other parts of the Pacific Northwest, causing billions of dollars of damage to homes and other structures each year. Conventional treatments use soil drenches or injections of liquid termiticides to create protective barriers around wooden structures.”

One of his research projects seeks to evaluate an alternative management tactic for subterranean termites: bait station systems that use insect growth regulator insecticides to eliminate entire termite colonies. “Bait systems represent reduced environmental contamination as compared to liquid treatments, but adoption of their use in California and other Western states has been slow to progress,” he said, adding that he hopes his research will demonstrate the relative efficacy of baits and increase both demand for and provision of bait services.

Sutherland,  who holds advanced degrees in entomology and horticulture from UC Davis and the University of Florida—including a doctorate in entomology from UC Davis in 2009-- is a Board-Certified Entomologist (Entomological Society of America certification program). He focuses his research on developing new IPM strategies or adapting and implementing current IPM strategies, in cooperation with other researchers, pest control operators, pest management professionals, public agencies, schools, parks, public housing, and regulatory agencies involved with household, structural, and industrial IPM.

His work includes education about IPM principles, development of IPM programs for clientele, reduction in unnecessary pesticide applications, and mitigation of surface water contamination due to urban pesticide applications. 

See more information on termites on the UC Statewide Integrated Pest Management (UC IPM) site, Subterranean and Other Termites.