My laboratory group examines the ecology of predators, pathogens and parasitoids that attack insect herbivores. Recently, we have also gotten interested in ecological solutions to food-safety problems, and in managing insect vectors of human pathogens. We combine experimental, molecular, and mathematical approaches, working at the interface between basic and applied ecology. Natural herbivore and pathogen suppression is a rigorous test of how well we really understand ecological interactions, as we attempt to manipulate human-managed systems to make pest/disease outbreaks less likely.

Currently, we have several ongoing projects in the lab:

Biodiversity and Natural Pest Suppression (BAN-PestS)

We are examining the ecological basis of natural pest control on west coast vegetable farms. Our central hypothesis is the increasing biodiversity among predators, parasitoids, and entomopathogens leads to increasingly pest-suppressive farms. Also, we are examining whether increasingly nutrient-rich soils on organic farms encourage “healthier” plants that are better able to defend themselves against pests. Intensive on-farm work is complemented by molecular gut-content analysis to delineate predator-prey interactions, and an examination of plant defensive-gene activity in a search for links between soil quality and plant “health”. More information

Avian Biodiversity: Impacts, Risks and Descriptive Survey (A-BIRDS)

Wild birds eat a wide variety of herbivorous insects, and so make an important contribution to natural pest control. At the same time, songbirds often transmit pathogens and parasites that can harm livestock and humans. Working on organic farms located all down the west coast, we are examining the benefits and possible harms of wild-bird conservation. Birds’ feeding habits are being tracked using molecular diet analysis and bird-exclusion experiments; we are trapping birds to assess their parasite and pathogen loads; and Nature Conservancy collaborators are helping us understand how landscape structure impacts bird populations and biodiversity. Our outreach efforts are in collaboration with the Cornell Laboratory of Ornithology.

A Natural Approach to Human Pathogen Suppression

On vegetable farms, outbreaks of harmful strains of E. coli or other pathogens can have devastating effects on human health and farm viability. These outbreaks are thought to sometimes result from fecal contamination of fields by deer, songbirds and other visiting wildlife. To avoid these risks, farmers feel increasing pressure to remove all native vegetation from their farms, along with erecting large deer fences and even draining ponds or other wetlands. This runs counter to abundant evidence that greater on-farm biodiversity makes it less likely that pests or pathogens will reach outbreak levels. We are examining whether the conservation of coprophagous dung beetles and other insects, and of beneficial soil microbes, can render farms unlikely to harbor human pathogens. That is, we suspect that greater farm biodiversity may be the solution to, rather than the cause of, outbreaks of human pathogens. More information

Mapping and Predicting Movement of Disease Vectors into Potato Crops

Zebra chip disease poses a major threat to the huge potato-growing industries in WA, OR and ID. The pathogen is transmitted by a small, highly-mobile insect, the potato psyllid. We had initially thought that the insect was rare in the Pacific Northwest (PNW), and the pathogen entirely absent – a false sense of security broken when massive zebra chip outbreaks in our region were quickly followed by the discovery of robust psyllid populations. Working with a large interdisciplinary team, we are studying the ecology of both vector and pathogen in the PNW. We are tracking and mapping psyllid populations across a broad area, and using cutting-edge population genetics approaches to infer psyllid movement patterns. In turn, this information will be used to develop predictive models of psyllid (and pathogen) spread, ultimately delivered to growers using a mobile-device-enabled web site.

Lethal and Non-Lethal Effects of Predators on Mosquitoes

Mosquitoes vector many diseases of humans, livestock, and wildlife. Among these is the mosquito Culex pipiens, which in our region is a key vector of West Nile Virus. Fortunately, in their aquatic larval stages, mosquitoes are attacked by a diverse community of predatory insects that have the potential to greatly reduce mosquito densities. In addition to these lethal effects, the predators also force mosquitoes to change their behavior – hiding more, feeding less – in order to lower the mosquitoes’ risk of being preyed upon. We are examining (1) how land-use patterns impact mosquito-predator biodiversity, (2) how predator biodiversity impacts mosquito survival and condition through both lethal and non-lethal channels, and (3) how resulting effects on mosquito adult size and longevity impact the insects’ ability to vector pathogens.

The Ecology of Potato Agroecosystems

The longest-running research project in the laboratory examines predator-prey, and herbivore-plant, interactions in northwest potato crops. Potatoes are the #2 dollar-value crop in Washington, second only to apples. This important crop is threatened by a remarkably diverse, and seemingly ever-changing, community of herbivorous insects. A vigorous organic sector provides the opportunity to examine how different farming systems impact ecological interactions. Various projects in the laboratory are:

1. Determining the relationship between natural enemy biodiversity and the strength of herbivore suppression
2. Delineating predator-prey relationships using molecular gut-content analysis
3. Examining the ecology of the potato psyllid, including its genetic population structure, use of non-crop host plants, and movement across the landscape
4. Exploring the relationship between soil and plant “health”, and whether soil management practices can influence the potato plant’s ability to defend itself against herbivores

If any of these projects piques your interest, or if you are excited about other, related research directions, please check out Opportunities for undergraduate, graduate, and postdoctoral research in the Snyder lab.