I am currently a research associate at Oregon State University in the Department of Crop and Soil Science. Recently I have been working on the interacting effects of competition and herbivory on population growth rates of tansy ragwort. I am teaching Introduction to Weed Management at OSU and will be helping Dr. Andy Hulting (another Mortensen lab alumni) with weed extension talks in Oregon.

My work in Pennsylvania focused on the mechanisms and consequences of dispersal of horseweed, Conyza canadensis. Horseweed has wind dispersed seeds that are often transported long-distances (hundreds to thousands of meters) in air currents. I studied the rate of spread of horseweed in areas where some populations are resistant to the herbicides commonly used to manage it and how current weed management strategies may facilitate spread of the weed. The research is exciting because it combines ecology, modeling, and meteorology and challenges the current understanding of resistance management.

Contact Joe.


  • Dauer, J., D.A. Mortensen and R. Humston. 2006. Controlled experiments to predict horseweed (Conyza canadensis) dispersal distances. Weed Science 54:484-489.
  • Skarpaas, O., J. T. Dauer, C. M. Schwarz, E. S. J. Rauschert, E. Jongejans, R. Jabbour, D. A. Mortensen, S. A. Isard, D. A. Lieb, Z. Sezen, A. G. Hulting, M. J. Ferrari, K. Shea, and E. S. Long. 2007. Dispersal: a synthesis of concepts, patterns and processes across organisms. Ecology Letters (in review).
  • Dauer, J., D.A. Mortensen, and M. VanGessel. 2007. Spatial and temporal dynamics governing long distance dispersal of Conyza canadensis. Journal of Applied Ecology 44:105-114
  • Menalled, F.D., R.G. Smith, J. T. Dauer, and T. Fox. 2007. Impact of Agricultural Management Systems on Carabid beetle communities and Invertebrate weed seed predation. Agriculture, Ecosystems and Environment 118: 49-54.
  • E.J. Shields, Dauer, J.T., VanGessel, M.J., Neumann, G. 2006. Horseweed (Conyza canadensis) seed collected in the planetary boundary layer. Weed Science 54:1063-1067.