Skip to main content Skip to navigation
Crowder Laboratory WSU Department of Entomology

Current Research Projects

Can sustainable agriculture promote diverse insect communities and ecosystem services?

Agricultural intensification degrades the biodiversity of insect communities and their ecological services. Evidence suggests, however, that organic and/or sustainable agricultural practices may promote diversity and aid in restoring communities. Our research attempts to determine the effects of agricultural practices, including comparisons of conventional vs. organic, on the structure of insect communities, and determine the consequences of these variable community structures on ecosystem services such as biological control and pollination.

Representative publications:

  • Smith OM, Cohen AL, Reganold JP, Jones MS, Orpet RJ, Taylor JM, Thurman JH, Cornell KA, Olsson RL, Ge Y, Kennedy CM, Crowder DW (2020) Landscape context affects the sustainability of organic farming systems. Proceedings of the National Academy of Sciences USA, in press (DOI:
  • Orpet RJ, Jones VP, Beers EH, Reganold JP, Goldberger JR, Crowder DW (2020) Perceptions and outcomes of conventional vs. organic apple orchard management. Agriculture, Ecosystems, and Environment 289, 106723.
  • Smith OM, Cohen AL, Rieser CJ, Davis A, Taylor JM, Adesanya AW, Jones MS, Meier AR, Reganold JP, Orpet RJ, Northfield TD, Crowder DW (2019) Organic farming promotes reliable environmental benefits but increases variability in crop yields: a global meta-analysis. Frontiers in Sustainable Food Systems 3, 82
  • Jones MS, Wright SA, Smith OM, Besser TE, Headrick DH, Reganold JP, Crowder DW, Snyder WE (2019) Organic farms conserve a dung beetle species capable of disrupting fly vectors of foodborne pathogens. Biological Control 137, 104020.
  • Lichtenberg EM, …(62 authors)…, Crowder DW (2017) A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes. Global Change Biology 23, 4946-4957.
  • Crowder DW, Reganold JD (2015) Financial performance of organic agriculture on a global scale. Proceedings of the National Academy of Sciences, 112 7611-7616.
  • Crowder DW, Jabbour R (2014) Relationships between biodiversity and biological control in agroecosystems: current status and future challenges. Biological Control 75, 8-17.
  • Crowder DW, Northfield TD, Gomulkiewicz R, Snyder WE (2012) Conserving and promoting evenness: Organic farming and fire-based wildland management as case studies. Ecology 93:2001-2007.
  • Crowder DW, Northfield TD, Strand MR, Snyder WE (2010) Organic agriculture promotes evenness and natural pest control. Nature 466:109-112.

Promoting pollinator health and pollination services

Abundant and diverse pollinator communities are critical for sustainable crop yields, yet the services provided by pollinators on farms are often threatened by abiotic and biotic stressors. We are currently working on a project to assess pollinator community health and pollination services in the Puget Sound Region, while educating local community members to increase pollinator literacy. Our research takes place primarily on diversified organic farms and urban gardens in collaboration with an active group of growers. We also have several citizen science initiatives as part of our Citizen Science Initiative for Bees.

  • Bloom EH, Northfield TD, Crowder DW (2019) A novel application of the Price equation reveals that landscape diversity promotes the response of bees to rare plant species. Ecology Letters 22, 2103-2110.
  • Bloom EH, Crowder DW (2020) Educational courses and passive methods attract citizen scientists and increase data collection. Citizen Science: Theory and Practice 5, 3.
  • Bloom EH, Crowder DW (2016) Biological control and pollination services on organic farms. In Advances in Insect Control and Resistance Management (eds Horowitz AR, Ishaaya I). Springer, New York, USA, pp 27-46.
  • Bloom EH, Olsson RL, Wine EH, Schaeffer RN, Crowder DW (2018) Managing cavity-nesting wild bees in Western Washington. Washington State University Extension, FS293E, 8 pp.
  • Bloom EH, Olsson RL, Crowder DW (2017) A citizen science guide to wild bees and floral visitors in western Washington. Washington State University Extension, EM110E, 17 pp.

Landscape ecology

Agricultural systems in Washington and many other states are diverse, yet we often lack a basic understanding of how insects move across landscapes, and how landscape diversity and configuration affects the distribution of pests and beneficial species. Our research seeks to identify how characteristics of landscapes (i.e., habitat diversity and configuration) affect insect distributions and their associations with plants.

Representative publications:

  • Illan JG, Bloom EH, Wohleb CH, Wenninger EJ, Rondon SI, Jensen AS, Snyder WE, Crowder DW (2020) Landscape structure and climate drive population dynamics of an insect vector within intensely managed agroecosystems. Ecological Applications, in press.
  • Bloom EH, Northfield TD, Crowder DW (2019) A novel application of the Price equation reveals that landscape diversity promotes the response of bees to rare plant species. Ecology Letters 22, 2103-2110.
  • Thurman JH, Crowder DW, Northfield TD (2017) Biological control agents in the Anthropocene: current risks and future options. Current Opinion in Insect Science 23, 59-64.
  • Cohen AL, Crowder DW (2017) The impacts of spatial and temporal complexity across landscapes on biological control. Current Opinions in Insect Science 20, 13-18.
  • D’Auria EM, Wohleb CH, Waters TD, Crowder DW (2016) Seasonal population dynamics of three potato pests in Washington State. Environmental Entomology 45, 781-789.
  • Milosavljevic I, Esser AD, Crowder DW (2016) Effects of environmental and agronomic factors on soil-dwelling pest communities in cereal crops. Agriculture, Ecosystems and Environment 225, 192-198.
  • Schmidt-Jeffris RA, Beers EH, Crowder DW (2015) Phytoseiids in Washington commercial apple orchards: biodiversity and factors affecting abundance. Experimental and Applied Acarology 67, 21-34.
  • Crowder DW, Dykstra EA, Brauner JM, Duffy A, Reed C, Martin E, Peterson W, Carriere Y, Dutilleul P, Owen JP (2013) West Nile virus prevalence across landscapes is mediated by local effects of agriculture on vector and host communities. PLoS ONE 8, e55006.
  • Carrière Y, Ellers-Kirk C, Hartfield K, Larocque G, Degain B, Dutilleul P, Dennehy TJ, Marsh SE, Crowder DW, Li X, Ellsworth PC, Naranjo SE, Palumbo JC, Fournier A, Antilla L, Tabashnik BE (2012) Large-scale, spatially-explicit test of the refuge strategy for delaying insecticide resistance. Proceedings of the National Academy of Sciences USA 109:775-780.

Vector-borne pathogens

Many insects transmit pathogens that threaten the health of humans, livestock, and wildlife. Our laboratory is exploring the dynamics of several insect-plant-pathogen systems, including the transmission of Pea-enation mosaic virus by pea aphids to pea plants and the transmission of Liberibacter solanaceurum by psyllids to potato plants. Our work involves experimental approaches to elucidate the mechanisms governing pathogen spread, and quantitative approaches to model the spread of pathogens within crop fields.

Representative publications:

  • Bera S, Blundell R, Liang D, Crowder DW, Casteel CL (2020) The oxylipin signaling pathway is required for increased aphid attraction and retention on virus-infected plants. Journal of Chemical Ecology, in press.
  • Chisholm PJ, Eigenbrode SD, Clark RE, Basu S, Crowder DW (2019) Plant-mediated interactions between a vector and a non-vector herbivore promote the spread of a plant virus. Proceedings of the Royal Society of London Series B 286, 20191383.
  • Clark RE, Basu S, Lee BW, Crowder DW (2019) Tri-trophic interactions mediate the spread of a vector-borne plant pathogen. Ecology 100, e02879.
  • Crowder DW, Li J, Borer ET, Finke DL, Sharon R, Pattemore D, Medlock J (2019) Species interactions affect the spread of vector-borne plant pathogens independent of transmission mode. Ecology 100, e02782.
  • Molki B, Thi Ha T, Cohen AL, Crowder DW, Gang DR, Omsland A, Brown JK, Beyanal H (2019). The infection of its insect vector by bacterial plant pathogen “Candidatus Liberibacter solanacearum” is associated with altered vector physiology. Enzyme and Microbial Technology 129, 109358.
  • Chisholm PJ, Busch JW, Crowder DW (2019) Effects of life history and ecology on virus evolutionary potential. Virus Research 265, 1-9.
  • Chisholm P, Sertsuvalkul N, Casteel CL, Crowder DW (2018) Reciprocal plant-mediated interactions between a virus and a non-vector herbivore. Ecology 99, 2139-2144.
  • Reif KE, Palmer GH, Crowder DW, Ueti MW, Noh SM (2014) Restriction of Francisella novicida genetic diversity during infection of the vector midgut. PLoS Pathogens 10:e1004499.
  • Crowder DW, Dykstra EA, Brauner JM, Duffy A, Reed C, Martin E, Peterson, W, Carriere Y, Dutilleul P, Owen JP (2013) West Nile virus prevalence across landscapes is mediated by local effects of agriculture on vector and host communities. PLoS ONE 8:e55006.