Nathan Kleczewski Ph.D. – Extension Specialist, Plant Pathology

Duties:  Statewide research and extension responsibilities for disease management of field crops

           The goal of my research/extension program is to improve the management of diseases and productivity of field crops in Delaware.  My research program evaluates novel control strategies as components of the integrated management of corn, soybeans, wheat, and barley as well as select vegetable crops.  I work closely with other scientists to conduct research relevant to Delaware and the surrounding regions.  Results of my work are shared with regional stakeholders and are presented in peer-reviewed scientific journals, extension publications, conferences, and meetings.  Educational programs are aimed at increasing awareness, knowledge, and expertise in plant pathology of certified crop advisers, producers, and other stakeholders.

 Current research:

  • Best management practices for Fusarium Head Blight of wheat and barley
  • Profitable management of foliar diseases of wheat
  • Foliar diseases of corn and their relationship to stalk and root rots
  • Fungicide resistance development in foliar diseases of corn and soybean
  • Soybean Necrotic Vein Virus
  • Profitability of fungicide use in double crop soybean
  • Novel and practical management of Fusarium oxysporum and Phytophthora in watermelon
  • Assessment of fungicide and biological disease control programs in field crops and select vegetables and variety trial evaluation.


  • 2009 Ph.D. Plant Pathology, The Ohio State University
  • 2004 B.S. Plant Ecology and Organismal Biology, The University of Wisconsin-Oshkosh (Summa Cum Laude)
  • 2012-2013 Research Plant Pathologist, FMC Global Innovation Organization
  • 2010-2012 Post-Doctoral Researcher, Department of Botany and Plant Pathology, Purdue University
  • 2009-2010 Post-Doctoral Researcher, Department of Biology, Indiana University
Publications (Peer Reviewed)

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. and D. Egel. 2012.  Evaluation of triploid watermelon lines for resistance to Fusarium wilt, 2011.  Plant Disease Management Reports.

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., 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. 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.


Publications (Extension)

Kleczewski, N.M. et al. 2014.  Commercial Vegetable Production Recommendation Guide.  Cooperative Extension Service, University of Delaware, Newark, DE.

Kleczewski, N.M. 2014.   Cover Story-Coming Clean: Why greenhouse sanitation must be a priority.  Produce Grower Magazine.  Published online at http//

Kleczewski, N.M. and D. Egel. 2011. Fungicide resistance management for Indiana Vegetables. Purdue University Factsheet-BP-183-W.

Kleczewski, N.M., and D. Egel. 2011. Greenhouse sanitation for disease management. Purdue University Factsheet-HO-250-W.

Kleczewski, N.M., S.L. Flory, and G. Nice. 2011. An Introduction to Microstegium vimineum Japanese stiltgrass/Nepalese browntop) an Emerging Invasive Grass in the Eastern United States.  Purdue University Factsheet-WS-49-W.

Kleczewski, N.M., P. Bonello, and J. Chatfield. 2009. Pruning and Care of Tree Wounds. Ohio State Factsheet-HYG-3311-09.

Kleczewski, N.M., and D. Lewandowski. 2009.  Virus Diseases of Greenhouse Floral Crops. Ohio State Factsheet-HYG-3065-08.

Kleczewski, N.M, and P. Bonello. 2008. Sudden Oak Death. Ohio State Factsheet-HYG-3309-08.

Kleczewski, N.M., and P. Bonello. 2008. Mycorrhizae in Urban Settings. Ohio State Factsheet-HYG-3305-08.

Kleczewski, N.M., and P. Bonello. 2007. Mycorrhizal inoculations of disturbed soils: What do we know? The Buckeye Arborist 38: 12-14.

Kleczewski, N.M. and P. Bonello. 2007. Mycorrhizal inoculations of disturbed soils: What do we know? The Ohio Woodland Journal 14: 14-15.

Kleczewski, N.M., and P. Bonello. 2007. Feature Article: Commercial inoculation of trees in urban soils:  More questions than answers. The Buckeye, January: 1-8.



2014 The American Phytopathological Society

APS Leadership Institute Fellowship

2008  The Ohio State University Department of Plant Pathology

C. C. Allison Award for Research and Service

2007 American Phytopathological Society

Kenneth Barker Student Travel Award

2004 University of Wisconsin-Oshkosh

Outstanding Biology Major Award

2003 University of Wisconsin-Oshkosh

-Leslie-Allen Fellowship in Ecology and Field Biology

-Excellence in Scholarship Award

2001 University of Wisconsin-Oshkosh

Outstanding Student in General, Organic, and Biochemistry


Memberships and Service

American Phytopathological Society

NCERA 137: Soybean Diseases

NCERA 184: Wheat Diseases

Corn Disease Working Group

Southern Soybean Disease Working Group

Sigma Xi


Financial Support Recieved (2014 +)

United States Wheat and Barley Scab Initiative                            $14,158

               Integrated Management of Delaware Wheat

               N. M. Kleczewski (PI)

 Delaware Crop Improvement Board                                                   $2,000

               Examination of fungicide programs in Delaware wheat

               N.M. Kleczewski (PI)

 Delaware Soybean Board

               A Survey of Soybean Necrotic Vein Virus in Delaware                 $9,164

               N. M. Kleczewski (PI)


Reviewing Activities

American Journal of Botany

Crop Protection

Ecological Letters

Fungal Ecology

Letters in Applied Microbiology

Journal of Medicinal Plants Research

Journal of Bacteriology Research

Microbial Ecology

Plant Disease

Plant and Soil