Nathan Michael Kleczewski

Research Assistant Professor and Faculty Extension Specialist

Dr. Kleczweski identifies and addresses plant diseases impacting soybean, corn, and small grain production. His research increases producer productivity and profitability across the globe. He currently has openings for students interested in pursuing a Master's degree in management of Fusarium head blight in wheat, Red crown rot in soybeans, and tar spot in corn.


Primary Disciplines


  • Ph.D. Plant Pathology. 2009. The Ohio State University
  • B.S. Ecology and Organismal Biology (EEOB) Plant Science Emphasis 2004. The University of Wisconsin-Oshkosh

Academic Positions

  • Extension Field Crop Plant Pathologist. University of Delaware. May 2013- October 2017.
  • Postdoctoral Researcher. Vegetable Pathology. Purdue University. 2010-2012
  • Postdoctoral Researcher. Plant Microbe Interactions. Indiana University. 2009-2010

Research Interests

  • Current general project areas include: 1) understanding the biology and ecology of corn tar spot and how this affects disease management, 2) assessing the impact and management of nematodes in corn, 3) understanding red crown rot in Illinois soybeans, and 4) improving Fusarium head blight management in wheat, 5) mycorrhizae in field crop systems
  • The Kleczewski lab develops practical, unbiased, science-based solutions for disease management of soybean, corn, small grain, and hemp production. Projects link basic lab science to practical, large scale disease production/management practices and tools for use by the general agricultural community.
  • Focal areas of study: Plant pathology, crop protection, disease management, disease identification, mycology, microbial ecology

Honors, Recognition, and Outstanding Achievements

  • C.S. Allison Award for Outstanding Graduate Research and Teaching in Plant Pathology. The Ohio State University
  • Outstanding Biology Major. The University of Wisconsin-Oshkosh
  • Excellence in Scholarship Award. The University of Wisconsin-Oshkosh
  • Leslie-Allen Fellowship in Ecology and Field Biology. The University of Wisconsin-Oshkosh

Selected Articles in Journals

  • Kleczewski N. and N Bowman. An observation on dispersal of the corn tar spot pathogen Phyllachora maydis from agronomic fields to an isolated urban location. Plant Health Progress. Accepted 11/20
  • Petrovic, K., Skaltsas, D., Castlebury, L., Kontz, B., Allen, T., Chilvers, M.I., Gregory, N.F., Kelly, H.M., Koehler, A.M., Kleczewski, N. and Mueller, D.S., 2020. Diaporthe seed decay of soybean [Glycine max (L.) Merr.] is endemic in the United States, but new fungi are involved. Plant Disease Accepted 11/20
  • Kaur N, Mullins C, Kleczewski N, Mehl HL. Occurrence of quinone outside inhibitor (QoI) resistance in Virginia populations of Parastagonospora nodorum infecting wheat. Plant Disease. 2020 Oct 1
  • Daren S Mueller, Kiersten A Wise, Adam J Sisson, Tom W Allen, Gary C Bergstrom, Kaitlyn M Bissonnette, Carl A Bradley, Emmanuel Byamukama, Martin I Chilvers, Alyssa A Collins, Paul D Esker, Travis R Faske, Andrew J Friskop, Austin K Hagan, Ron W Heiniger, Clayton A Hollier, Tom Isakeit, Tamra A Jackson-Ziems, Douglas J Jardine, Heather M Kelly, Nathan M Kleczewski, Alyssa M Koehler, Steve R Koenning, Dean K Malvick, Hillary L Mehl, Ron F Meyer, Pierce A Paul, Angie J Peltier, Paul P Price, Alison E Robertson, Gregory W Roth, Edward J Sikora, Damon L Smith, Connie A Tande, Darcy EP Telenko, Albert U Tenuta, Lindsey D Thiessen, William J Wiebold. 2020. Corn yield loss estimates due to diseases in the United States and Ontario, Canada from 2016 to 2019. Plant Health Progress 21:4
  • Kleczewski, N., Plewa, D., Bissonnette, K.M., Bowman, N.D., Byrne, J.M, LaForest, J., Dalla-Lana, F. Malvick, D.K., Mueller, D.S., Chilvers, M.I., Paul, P.A., Raid, R.N., Robertson, A.E., Ruhl, G.E., Smith, D.L., and D.E.P. Telenko. 2020. Documenting the Establishment, Spread, and Severity of Phyllachora maydis on Corn, in the United States, Journal of Integrated Pest Management, Volume 11, Issue 1, 2020, 14,
  • J. Valle-Torres, T. J. Ross, D. Plewa, M. C. Avellaneda, J. Check, M. I. Chilvers, A. P. Cruz, F. Dalla Lana, C. Groves, C. Gongora-Canul, L. Henriquez-Dole, T. Jamann, N. Kleczewski, S. Lipps, D. Malvick, A. G. McCoy, D. S. Mueller, P. A. Paul, C. Puerto, C. Schloemer, R. N. Raid, A. Robertson, E. M. Roggenkamp, D. L. Smith, D. E. P. Telenko, and C. D. Cruz. 2020. Tar Spot: An Understudied Disease Threatening Corn Production in the Americas. Plant Disease.
  • Anderson, N., A. N. Freije, G. C. Bergstrom, C. A. Bradley, C. Cowger, T. Faske, C. Hollier, N.M. Kleczewski, G. B. Padgett, P. Paul, T. Price, and K. A. Wise. 2020. Sensitivity of Fusarium graminearum to Metconazole and Tebuconazole fungicides before and after widespread use in wheat in the United States 3 Apr.
  • Groves, C.G, N.M Kleczewski, D.E.P. Telenko, M. Chilvers, and D.L. Smith. 2020. Phyllachora maydis ascospore resease and germination from overwintered corn residue. Plant Health Progress. doi:10.1094/PHP-10-19-0077-RS
  • Kleczewski, N.M., Butts-Willmsmeyer, C.J. and C. Scanlan. 2020. Assessing the curative and protective impact of select fungicides for control of powdery mildew of wheat. Plant Disease accepted 11/2019
  • Kleczewski, N.M., Donnelly, J. and Higgins, R., 2019. Phyllachora maydis, causal agent of tar spot on corn, can overwinter in northern Illinois. Plant Health Progress 31 July.
  • Willbur, J.F., Mitchell, P.D., Fall, M.L., Byrne, A.M., Chapman, S.A., Floyd, C.M., Bradley, C.A., Ames, K.A., Chilvers, M.I., Kleczewski, N.M. and Malvick, D.K., 2019. Meta-analytic and economic approaches for evaluation of pesticide impact on Sclerotinia stem rot control and soybean yield in the north central United States. Phytopathology pp.PHYTO-04.
  • Kleczewski, N.M., Kangas, C, Phillipi, E., Plewa, D., and V. Kleczewski. 2019. First report of Caolnectria ilicicola (syn Cylindrocladium parasiticum) causing red crown rot on soybeans in Illinois. Plant Disease. doi:10.1094/PDIS-01-19-0105-PDN
  • Dalle-Lana, F., D. Plewa, N.M. Kleczewski, and P.Paul. 2019. First report of Phyllachora maydis causing tar spot of corn in Ohio. Plant Disease. doi:10.1094/PDIS-01-19-0070-PDN
  • Opoku, J., N. M. Kleczewski, K. Hamby, D. A. Herbert, S. Malone, and H. Mehl. 2019. Relationship between invasive brown marmorated stink bug (Halyomorpha halys) and fumonisin contamination of field corn in the mid-Atlantic U.S. Plant Disease
  • G. Zhang, T. W. Allen, J. P. Bond, A. M. Fakhoury, A. E. Dorrance, L. Weber, T. R. Faske, L. J. Giesler, D. E. Hershman, B. S. Kennedy, D. L. Neves, C. A. Hollier, H. M. Kelly, M. A. Newman, N. M. Kleczewski, S. R. Koenning, L. D. Thiessen, H. L. Mehl, T. Zhou, M. D. Meyer, D. S. Mueller, Y. R. Kandel, P. P. Price III, J. C. Rupe, E. J. Sikora, J. R. Standish, M. Tomaso-Peterson, K. A. Wise, and C. A. Bradley. 2018. Widespread occurrence of quinone outside inhibitor fungicide-resistant isolates of Cercospora sojina, causal agent of Frogeye leaf spot in soybean, in the United States. Plant Health Progress doi:10.1094/PHP-04-18-0016-RS 8 November.
  • Paul, P. A., J. D. Salgado, G. C. Bergstrom, C. Bradley, E Byamukama, A. M. Byrne, V. Chapara, J. A. Cummings, M. I. Chilvers, R. Dill-Macky, A. J. Friskop, N. M. Kleczewski, L. V. Madden, M. Nagelkirk, J. Stevens, M. Smith, S. N. Wegulo, K. A. Wise and D. Yabwalo. 2018. Integrated Effects of Genetic Resistance and Prothioconazole + Tebuconazole Application Timing on Fusarium Head Blight in Wheat. Plant Disease. doi:10.1094/PDIS-04-18-0565-RE
  • Sylvester, P., Dalle Lana, F. Mehl, H., Collins, A, Paul, P, and N. Kleczewski. 2018. Evaluating the profitability of foliar fungicide programs in mid-Atlantic soft-red winter wheat production Plant Disease 102(8): 1627-1637
  • Egel. D., Kleczewski, N., Mumtaz, F., and R. Foster. Acibenzolar-S-methyl is associated with yield reduction when used for managing bacterial wilt (Erwinia trachephila) in cantaloupe. Crop Protection 109-136-141.
  • Anderson, N. R., M. D. Irizarry, C. A. Bloomingdale, D. L. Smith, C. A. Bradley, D. P. Delaney, N. M. Kleczewski, E. J. Sikora, D. S. Mueller and K. A. Wise (2017). Effect of soybean vein necrosis on yield and seed quality of soybean. Canadian Journal of Plant Pathology 39(3): 334-341.
  • Kleczewski, N.M. 2018. Prevalence and cropping system impacts on soybean vein necrosis disease in Delaware soybeans. Plant Health Progress. 9 February.
  • Wyandandt, C.A., McGrath, M.A., Everts, K.A., Rideout, S.L., Guigino, B.L. and N. Kleczewski. 2018. Fungicide resistance management guidelines for Cucurbit downy and Powdery mildew control in the mid-Atlantic and Northeast regions of the United States, 2018. Plant Health Progress. 9 February.
  • Kleczewski, N. M. and C. Whaley 2018. Assessing the utility of the growth regulator trinexapac-ethyl and fungicides in mid-Atlantic soft red winter wheat production systems. Crop Protection 104: 60-64.
  • Sylvester, P. N. and N. M. Kleczewski 2018. Evaluation of foliar fungicide programs in mid-Atlantic winter wheat production systems. Crop Protection 103: 103-110.
  • T. W. Allen, C. A. Bradley, A. J. Sisson, E. Byamukama, M. I. Chilvers, C. M. Coker, A. A. Collins, J. P. Damicone, A. E. Dorrance, N. S. Dufault, P. D. Esker, T. R. Faske, L. J. Giesler, A. P. Grybauskas, D. E. Hershman, C. A. Hollier, T. Isakeit, D. J. Jardine, H. M. Kelly, R. C. Kemerait, N. M. Kleczewski, S. R. Koenning, J. E. Kurle, D. K. Malvick, S. G. Markell, H. L. Mehl, D. S. Mueller, J. D. Mueller, R. P. Mulrooney, B. D. Nelson, M. A. Newman, L. Osborne, C. Overstreet, G. B. Padgett, P. M. Phipps, P. P. Price, E. J. Sikora, D. L. Smith, T. N. Spurlock, C. A. Tande, A. U. Tenuta, K. A. Wise, and J. A. Wrather. 2017. Soybean yield loss estimates due to diseases in the United States and Ontario, Canada, from 2010 to 2014. Plant Health Progress. 13 April.
  • Jones, J., Kleczewski, N., Deseager, J., Meyer, S., and G. Johnson. 2017. Assessment of nematicides for control of southern root knot nematodes in Lima Beans. Crop Protection 96: 151-157.
  • Manamgoda, D.S., A. Minnis, N.M. Kleczewski, S.L. Flory, L.A. Castlebury, and K.D. Hyde. 2013. Bipolaris drechsleri sp. nov. Fungal Planet Description Sheets 213: 26.
  • Minnis, A., A.Y. Rossman, N.M. Kleczewski and S.L. Flory. 2012. Bipolaris microstegii sp nov. Fungal Planet Description Sheets 129: 151.
  • Bauer, J. T., N. M. Kleczewski, J. D. Bever, K. Clay and H. L. Reynolds. 2012. Nitrogen-fixing bacteria, arbuscular mycorrhizal fungi and the productivity and structure of prairie grassland communities. Oecologia 170(4): 1089-1098.
  • Kleczewski N. M., J. T. Bauer, J. D. Bever, K. Clay and H. L. Reynolds. 2012. A survey of endophytic fungi of switchgrass (Panicum virgatum) in the Midwest, and their putative roles in plant growth. Fungal Ecology 5(5):521-529.
  • Kleczewski N.M., D.A.Herms and P. Bonello. 2012. Nutrient and water availability alter belowground patterns of biomass allocation, carbon partitioning, and ectomycorrhizal abundance in Betula nigra. Trees: Structure and Function 26(2) 525-533.
  • Kleczewski N.M., S. L. Flory and K. Clay. 2012. Variation in pathogenicity and host range of Bipolaris sp. causing leaf blight disease on the invasive grass Microstegium vimineum. Weed Science 60(3):486-493.
  • Kleczewski N. M. and D. S. Egel, 2011. A diagnostic guide for Fusarium wilt of watermelon. Online. Plant Health Progress. doi:10.1094/PHP-2011-1129-01-DG.
  • Flory, S.L., N.M. Kleczewski, and K. Clay. 2011. Ecological consequences of pathogen accumulation on an invasive grass. Ecosphere 2(10):12 pp.
  • Kleczewski N.M. and S. L. Flory. 2010. A new leaf blight disease on the invasive grass Microstegium vimineum caused by a Bipolaris sp. Plant Disease 94(7): 807-811.
  • Kleczewski N.M., D.A.Herms, and P. Bonello. 2010. Effects of soil type, fertilization and drought on carbon allocation to root growth and partitioning between secondary metabolism and ectomycorrhizae of Betula papyrifera. Tree Physiology 30(7):807-817.