I joined the Entomology and Plant Pathology Department in January 2018. Prior to joining the EPP department I was a Post-Doctoral Associate at Cornell University in the laboratory of Dr. Sarah Pethybridge, where I worked on disease forecasting systems for a fungal disease of table beet called Cercospora leaf spot. I also received my Ph.D. in Plant Pathology at Cornell University under the advisement of Dr. Christine Smart working on diagnostics, population genetics, and management of tomato and potato late blight, caused by the oomycete Phytophthora infestans. I received my B.A. and M.S. degrees from Clemson University, where I worked on alternatives to chemical soil fumigation for vegetable disease management under the advisement of Dr. Anthony Keinath. I have also spent time in private industry as an arborist for Bartlett Tree Experts, as well as Plant Pathology Lead for Zymtronix Catalytic Systems Inc., where I conducted research towards commercializing a novel approach to plant disease management using enzymes. My research focuses on integrated approaches to improving specialty crop disease management. The purpose of my program is to support the specialty crops industry in the State of Tennessee, especially fruit and vegetable producers, through applied plant pathology research and extension, and to mentor undergraduate and graduate students.


Research focus

My academic appointment is 100% extension. My extension efforts are supported by an applied research program aimed at improving specialty crop disease management. Areas of research interest include sustainable disease management, cultural practices, improving chemical use efficiency, pathogen detection and diagnostics, population genetics of fungi and oomycetes, and monitoring for fungicide resistance. Research is largely guided by disease issues affecting Tennessee specialty crop producers, with the goal of mitigating losses to disease.


Extension and outreach focus

The goal of my extension program is to support Tennessee specialty crops producers through education programming aimed at improving disease management. Working closely with extension agents, education programs are focused on integrated pest management to promote effective and sustainable disease management practices. My applied research program supports these efforts by focusing on integrated disease management strategies including cultivar selection, cultural practices, biological and chemical control, and improved understanding of pathogen biology and disease epidemiology.


Teaching focus

I do not have an academic teaching appointment, but teaching is a major focus of my program through my extension efforts. Additionally, I am always interested in mentoring motivated students. I have an open-door philosophy, and I view my role as a mentor to push students to access their potential while providing guidance, resources, and direction to support their success.

zachariah hansen

Assistant Professor
office (865) 974-7784
fax (865) 974-4744

G059 McCord Hall
2640 Morgan Cir Drive
Knoxville, TN 37996-4560

B.A., Biological Science, Clemson University
M.S., Plant and Environmental Science, Clemson University
Ph.D. Plant Pathology, Cornell University

Professional appointment
100% Extension

Graduate program concentrations
Sustainable Disease and Integrated Pest Management Systems

Areas of expertise
Specialty crop disease management, pathogen detection and diagnostic

Sustainable agriculture, disease management, IPM, detection, diagnostics, population genetics, specialty crops, fruit, vegetables, fungi, oomycetes

Creative Art Microscope image

Research questions in our laboratory

  • What are the major diseases affecting Tennessee specialty crop producers?

    How are specialty crop diseases currently managed?

    How do cultural practices influence disease occurrence and severity?

    How does pathogen population structure affect disease epidemiology and management?

    Is there an opportunity to deploy host resistance as part of a disease management program?

    Are chemicals used to manage diseases effective?

    Does fungicide and antibiotic resistance exist in key pathogen populations in Tennessee, and how prevalent is that resistance?


Current lab members

Extension Publications

Pethybridge, S.J., Hansen, Z.R., Knight, N.L. 2017. Efficacy of fungicides for Cercospora leaf spot control in table beet, 2017. Plant Disease Management Reports issue:volume.

Hansen, Z.R., & Smart, C.D. 2013. Tomato variety trial for resistance to late blight, 2012. Plant Disease Management Reports 7:V090.

Smart, C.D., & Hansen, Z.R. 2012. 2012 trial of late blight resistance in tomato varieties. Veg Edge Vol. 8, issue 27. Cooperative Extension Publication, Cornell University.

Keinath, A.P., Hassell, R.L., DuBose, V.B., & Hansen, Z.R. 2012. Evaluation of three fumigants to control soilborne pathogens on processing tomato, 2011.Plant Disease Management Reports 6:V025.

Hansen, Z.R., Keinath, A.P., Baccari, G.V., & DuBose, V.B. 2011. Evaluation of brassica cover crops for control of root rot in peppers. Plant Disease Management Reports 5:V073.


Guarnaccia, V., Hansen, Z.R., Smart, C.D., & Polizzi, G. 2018. Characterisation and mefenoxam sensitivity of Phytophthora spp. from ornamental plants in Italian nurseries. Phytopathologia Mediterranea. In review.

Knight, N.L., Vaghefi, N., Hansen, Z.R., Kikkert, J.R., & Pethybridge, S.J. 2018. Temporal differentiation and shifts in genetic structure of Cercospora beticola populations in table beet fields of New York. Plant Disease, accepted.

Hansen, Z.R., Donnelly, M.K., & Corgié, S.C. 2017. In-vitro inhibition of Pythium ultimum, Fusarium graminearum, and Rhizoctonia solani by a stabilized lactoperoxidase system alone and in combination with five fungicides. Agronomy (7), 1-13.

Hansen, Z.R., Everts, K.L., Fry, W.E., Gevens, A.J., Grünwald, N.J., Gugino, B.K., Knaus, B.J., Johnson, D.A., Johnson, S.B., Judelson, H.S., McGrath, M.T., Myers, K.L., Ristaino, J.B., Roberts, P.D., Secor, G.A., & Smart, C.D. 2016. Genetic variation within clonal lineages of Phytophthora infestans revealed through genotyping-by-sequencing, and implications for late blight epidemiology. PLoSONE (11), e0165690.

Hansen, Z.R., Knaus, B.J., Tabima, J.F., Press, C.M., Judelson, H.S., Grünwald, N.J., & Smart, C.D. 2016. SNP-based differentiation of Phytophthora infestans clonal lineages using locked nucleic acid probes and high resolution melt analysis. Plant Disease (100), 1297-1306.

Hansen, Z.R., Knaus, B.J., Tabima, J.F., Press, C.M., Judelson, H.S., Grünwald, N.J., & Smart, C.D. 2016. Loop-mediated isothermal amplification (LAMP) for detection of the tomato and potato late blight pathogen, Phytophthora infestans. Journal of Applied Microbiology (120), 1010-1020.

Hansen, Z.R., Small, I.M., Mutschler, M., Fry, W.E., & Smart, C.D. 2014. Differential susceptibility of thirty nine tomato varieties to Phytophthora infestans clonal lineage US-23. Plant Disease (98), 1666-1670.

Guarnaccia, V., Hansen, Z.R., Aiello, D., Smart, C.D., & Polizzi, G. 2014. First detection of root rot and foliar blight on Pittosporum (Pittosporum tenuifolium) caused by Pythium irregulare in Italy. Journal of Phytopathology (163), 411-414.

Keinath, A.P., & Hansen, Z.R. 2013. Isolates of Didymella bryoniae from South Carolina remain sensitive to DMI fungicides despite multi-year exposure. Journal of Phytopathology (161), 315–323.

Hansen, Z.R., Keinath, A.P. 2012. Increased pepper yields following incorporation of biofumigation cover crops and the effects on soilborne pathogen populations and pepper diseases. Applied Soil Ecology (63), 67-77.

For complete list of publications please visit my