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Plant Pest Diagnostics Center

Fred Hrusa

Dr. Fred Hrusa

Senior Plant Taxonomist, Retired

Plant Pest Diagnostics Branch, California Department of Food & Agriculture
3294 Meadowview Road, Sacramento, CA 95832-1448, U.S.A.


Curriculum vitae


  • Doctor of Philosophy (Plant Biology) - University of California, Davis. 1995. Dissertation: "The systematics and evolution of Rhododendron occidentale (Torrey & A. Gray) A. Gray (section Pentanthera; subf. Rhododendroideae; Ericaceae)"
  • Master of Science (Botany) - University of California, Davis. 1991. Thesis: "A morphometric analysis of variation in Rhododendron occidentale (T. & G.) Gray, among populations native to ultrabasic and non-ultrabasic substrata (Ericaceae: Rhododendroideae)"
  • Bachelor of Science (Ornamental Horticulture) - California Polytechnic State University, San Luis Obispo. 1983.


  • 1997-2016, Senior Plant Taxonomist, California Department of Food and Agriculture


  1. Stebbins, G. L., & G.F. Hrusa. 1995. The North Coast Biodiversity Arena in Central California: A New Scenario for Research and Teaching Processes of Evolution. Madroño 42 (2): 269-294.
  2. Hrusa, G.F., & J.C. Hunter,1996. Black Butte Research Natural Area, Los Padres National Forest, San Luis Obispo County, California. Description, Vegetation and Flora. USDA Forest Service, Pacific SW Research Station, Albany CA. 94 pp.
  3. Brennan, E.B., R.J. Gill, G.F. Hrusa, & S.A. Weinbaum. 1999. First record of Glycaspis brimblecombei (Moore) (Homoptera: Psyllidae) in North America. The Pan-Pacific Entomologist, 75:11, 55-57.
  4. Hrusa, G.F. 1999. Limnobium spongia Sensu Lato. California Plant Pest and Disease Report 18(2): 46-49.
  5. Hrusa, G.F. 1999. The Salvinia auriculata Aubl. Complex (Salviniaceae). California Plant Pest and Disease Report 18(2): 43-45.
  6. Villegas, B., D.A. Mayhew, F. Hrusa, & J. Balciunas. 2000. Survey of Chaetorellia seedhead flies on Cirsium thistles in close proximity to Centaurea spp. in California. Pages 62-63 in D.M. Woods, ed. In, Biological Control Program Annual Summary, 1999. California Department of Food and Agriculture, Plant Health and Pest Prevention Services, Sacramento, CA.
  7. Brennan, E.B., G.F. Hrusa, S.A. Weinbaum & W. Levison. 2001. Resistance of Eucalyptus species to Glycaspis brimblecombei (Homoptera: Psyllidae) in the San Francisco Bay Area. The Pan-Pacific Entomologist 77(4). 249-253.
  8. Sorensen, J.T., F. Hrusa & T. Tyler, 2001. Origin of the Sudden Oak Death (SOD) pathogen and its potential impact: a working hypothesis. California Plant Pest and Disease Report 19 (3-6): 47-57 + maps.
  9. Hrusa, F., B. Ertter, A. Sanders, G. Leppig, & E. Dean 2002. Catalogue of non-native vascular plants occurring spontaneously in California beyond those addressed in the Jepson Manual - - Part I. Madroño 49(2): 61-98.
  10. Ayres, D., F. Ryan, F. Hrusa, & P. Akers, 2005. Tumbleweeds of California: Who, what, where and how. Poster presented at the Annual Meeting of the California Invasive Plants Council.
  11. Hrusa, G.F., & D. Kelch 2005. Significant Records in Botany: Cuscuta spp., Giant Dodders. California Plant Pest and Disease Report 23(12): 25-31.
  12. Gaskin, John F., Frederick J. Ryan, G. Frederic Hrusa, and Jason P. Londo, 2006. Genotype diversity of Salsola tragus and potential origins of a previously unidentified invasive Salsola from California and Arizona. Madroño 53(3): 244-251.
  13. Dean, E., G.F. Hrusa, G. Leppig, A. Sanders and B. Ertter, 2008. Catalogue of non-native vascular plants occurring spontaneously in California beyond those addressed in the Jepson Manual – Part II. Madroño 55(2): 93-112.
  14. Hrusa, G.F., & J.F. Gaskin, 2008. The Salsola tragus Complex in California (Chenopodiaceae): Characterization and Status of Salsola australis and the Autochthonous Allopolyploid Salsola ryanii sp. nov.  Madroño 55(2): 113-131.
  15. Kelch, D. & G.F. Hrusa. 2008. The Consortium of California Herbaria. California Plant Pest & Disease Report 24: 30-35.
  16. Hrusa, G.F. 2011. Significant Records in Botany: Branched Broomrape (Lamiales: Orobanchaceae: Orobanche ramosa). California Plant Pest & Disease Report 25: 4-5.
  17. Hrusa, G.F. 2012. Morphological and Isoenzyme Variation in Rhododendron occidentale (western azalea) (section Pentanthera; Ericaceae). Madroño 59(3): 128–142.
  18. Hrusa, G.F. 2012.  The genera Bassia, Corispermum, Cycloloma, Kochia, and Salsola, in The Jepson Manual, ed. 2, Vascular Plants of California, University of California Press, Berkeley, California.
  19. Hrusa, G.F. 2014. Diplacus bicolor, correct name in the genus Diplacus for Mimulus whitneyi (Phrymaceae). Phytoneuron 2014-17: 1. Open access
  20. Hrusa, G.F. 2014.  Two new subspecies of Gilia ochroleuca (Gilia sect. Arachnion: Polemoniaceae) from southwest-central California. Phytoneuron 2014-90: 1–16. Open access
  21. Brullo, C., Brullo, S., Gaskin, J.F., Del Galdo, G.G., Hrusa, G.F. & Salmeri, C. 2015. A new species of Kali (Salsoloideae, Chenopodiaceae) from Sicily, supported by molecular analysis. Phytotaxa 201 (4): 256–277.
  22. Hrusa, G.F. 2016. A new lectotype for Apiastrum angustifolium Nutt. var. tenellum Nutt. (Apiaceae). Phytoneuron 2016-16: 1-3. Open access