Greg Roth

Greg Roth

  • Emeritus Professor of Agronomy

Areas of Expertise

  • Grain crop management
  • Corn management and hybrid evaluation
  • Corn silage management
  • Soybean management and variety evaluation
  • Winter wheat management and variety evaluation
  • Winter barley management and variety evaluation
  • Interseeding cover crops in corn and soybeans


  • Ph.D., Agronomy, The Pennsylvania State University, 1987
  • M.S., Virginia Polytechnic Institute and State University, May 1981
  • B.S., The Pennsylvania State University, March 1979, Agronomy (with distinction)

Responsibilities and Interests

In my position as the extension grain crops specialist, I develop educational programs for extension agents, agribusiness groups and producers on timely issues such as managing crops during drought stress, GMO issues, potential of specialty corn hybrids, managing for grain quality, organic grain production and producing corn for silage. I also conduct applied field research on various issues. A key research focus has been managing corn for silage production using different hybrids and management strategies and then using various models to estimate the profitability of the these practices on dairy farms. We also evaluate the yield and quality traits of transgenic corn hybrids and their adaptability to our region. We are also studying the potential of added value wheat and barley varieties to try to create more opportunities for crop producers in the state.  I am also working with a team to develop a machine to interseed cover crops into growing corn.


  • 75% Extension
  • 25% Research


Professional Background

  • 5/87 - Research Associate, Department of Agronomy, The Pennsylvania State University
  • 5/89 - Assistant Professor of Agronomy, Department of Agronomy, The Pennsylvania State University
  • 7/95 - Associate Professor of Agronomy, Department of Agronomy, The Pennsylvania State University
  • 7/02 - Professor of Agronomy, Department of Crop & Soil Sciences, The Pennsylvania State University

Selected Publications

  1. Prasad, R., S.K. Gunn, C.A. Rotz, H. Karsten, G. Roth, A. Buda, and A.M.K. Stoner. 2018. Project climate and agronomic implications for corn production in the Northeastern United States. PLOS ONE 13(6): e0198623
  2. Harper, J.K., G.W.Roth, B. Garalejic, and N. Skrbic.  2018.  Programs to promote adoption of conservation tillage:  A Serbian case study.  Land Use Policy, Volume 78, November 2018, Pages 295-302.
  3. Curran, W., R. Hoover, S. Mirsky, G. Roth, M. Ryan, V. Ackroyd, J. Wallace, M. Dempsey, and C. Pelzer.  2018.  Evaluation of cover crops drill interseeed into corn (Zea mays L.) across the Mid-Atlantic region.  Agron. J. In Press. (doi: 10.2134/agronj2017.07.0395). 

  4. Baldin M, Ying Y, Fan Y, Roth G, Casper DP, Harvatine KJ. Characterization of linoleic acid (C18:2) concentration in commercial corn silage and grain hybrids. J Dairy Sci. 2018 Jan; 101(1):222-232. PMID: 29103704.
  5. Harper, M.T., J. Oh,  F. Giallongo,  J.C. Lopes, G.W. Roth, A.N. Hristov. 2017. Using brown midrib 6 dwarf forage sorghum silage and fall-grown oat silage in lactating dairy cow rations. Journal of Dairy Science 100 (7):5250 - 5265.
  6. Harper, M.T.,  J. Oh, F. Giallongo, G.W. Roth , A.N. Hristov.  2017. Inclusion of wheat and triticale silage in the diet of lactating dairy cows.  Journal of Dairy Science , Volume 100(8):6151 – 6163.
  7. Hristov, A.N., A.T. Degaetano, C.A.Rotz, E. Hoberg, R.H. Skinner, T. Felix, H. Li, P.H. Patterson, G. Roth, M. Hall, T.L. Ott, L.H. Baumgard, W. Staniar, R.M. Hulet, C. J. Dell, A.F. Brito, D. Y. Hollinger.  2017.  Climate change effects on livestock in the Northeast US and strategies for adaptation.  Climatic Change, () 1-13,  DOI 10.1007/s10584-017-2023-z
  8. Kucek, L.K., E. Dyck, J Russel, L. Clark, J. Hammelman, S. Burns-Leader, S. Senders, J. Jones, D. Benscher, M. Davis, G. Roth, S. Swinger, M. E. Sorrells and J. C. Dawson. 2017.  Evaluation of wheat and emmer varieties for artisanal baking, pasta making, and sensory quality.  Journal of Cereal Science 74: 19-27.
  9. Julius, C. P.H. Heinemann, D. H. Schaufler, G.W. Roth, J. Liu, and A.L . Boehman.  2016.  Straight Vegetable Oil as a Replacement Fuel for Diesel:  Comparing Tractor Performance in Stationary and Field Tests.  Trans. ASAE 59(5): 1137-1148. ISSN 2151-0032 DOI 10.13031/trans.59.11701
  10. Mueller, D.S., Wise, K.A., Sisson, A.J., Allen, T.W., Bergstrom, G.C., Bosley, D.B., Bradley, C.A., Broders, K.D., Byamukama, E., Chilvers, M.I., Collins, A., Faske, T.R., Friskop, A.J., Heiniger, R.W., Hollier, C.A., Hooker, D.C., Isakeit, T., Jackson-Ziems, T.A., Jardine, D.J., Kinzer, K., Koenning, S.R., Malvick, D.K., McMullen, M.,Meyer, R.F., Paul, P.A., Robertson, A.E., Roth, G.W., Smith, D.L., Tande, C.A., Tenuta, A.U., Vincelli, P. Warner, F. 2016. Corn yield loss estimates due to diseases in the United States and Ontario, Canada from 2012 to 2015. Plant Health Progress 17:211-222. doi:10.1094 / PHP-RS-16-0030
  11. Adler, P.R., B.M. Rau and G.W.Roth. 2015 Sustainability of corn stover harvest strategies in Pennsylvania BioEnergy Research DOI 10.1007/s12155-015-9593-2
  12. Ciolkosz, D., R. Hilton, C.Swackhammer, H.Yi, V.M. Puri, D. Swomely, and G. Roth. 2014. Farm scale biomass pelletizer performance for switchgrass pellet production. Applied Engineering in Agriculture. 31(4): 559-567. (doi: 10.13031/aea.31.10803)
  13. Roth, G.W., C. Dillon, W.Curran, C.Houser, W.S Harkcom.2015.  Apparatus and method for no-till inter-row simultaneous application of herbicide and fertilizer, soil preparation, and seeding of a cover crop in a standing crop, U.S. Patent 20120260836, Issued April 14, 2015.
  14. Lauer, J.G., G. W. Roth, and M.Zarnstorff. 2014 Predicting grain yield using starch content and adjuster methods.  Agronomy Journal 106:2209-2214.
  15. Karlen, D.L., S.J. Birrell, J.M.F. Johnson, S. L. Osborne, T. E. Schumacher, G.E. Varvel, R.B. Ferguson, J.M. Novak, J.R. Frederick, J.M. Baker, J. A. Lamb, P.R. Adler, G.W. Roth, and E.D. Nafzinger. 2014.  Multilocation corn stover harvest effects on crop yields and nutrient removal.  Bioenergy Research. DOI 10.1007/s12155-014-9419-7.
  16. Mebane, V.J., R.L.Day, J.M Hamlett J. E. Watson and G.W. Roth.  2013. Validating the FAO Aquacrop model for rainfed maize in Pennsylvania.  Agronomy Journal 105:419-427
  17. Houser, C.D., G.W. Roth and D. M. Beyer. 2013. Potential of spring stover harvest to mitigate stover removal impacts.  Crop Management   12: DOI 10.1094/CM-2013-0062-RS
  18. Bohnenblust, E., Breining, J., Shaffer, J., Fleischer, S., Roth, G., Tooker, J. 2013. Current European Corn Borer, Ostrinia nubilalis, Injury Levels in the Northeastern US and the Value of Bt Field Corn. Pest Management Science. DOI: 10.1002/ps3712.
  19. Bohnenblust, E., Breining, J., Roth, G. and Tooker, J. (2013), Corn pith weevil, Geraeus penicillus (Coleoptera: Curculionidae), in transgenic, insect-resistant and conventional field corn hybrids. Journal of Applied Entomology. doi: 10.1111/jen.12051
  20. Bohnenblust, E., Breining, J., Fleischer, S., Roth, G., Tooker, J. 2013. Corn Earworm in Northeastern Field Corn: Pest Threat and the Value of Transgenic Hybrids. Journal of Economic Entomology. 106 (3): 1250-1259.
  21. Isaza, L.A., K. Opelt, T. Wagner, E. Mattes, E. Bieber, E.O. Hatley, G.W. Roth, J. Sanjaun, H. Fischer, H. Sandermann, A. Hartmann, and D. Ernst.  2011.  Lack of glypohosate resistance gene transfer from Roundup Ready Soybean to Bradyrhizobium japonicum under field and laboratory conditions. Z. Naturforsh. 66c: 595-604.
  22. Karlen, D.L., G.E.Varvel, J.M.F. Johnson, J. M. Baker, S. L. Osborne, J. M. Novak, P.R. Adler, G.W. Roth, and S. J. Birrell.  2011.  Monitoring soil quality to assess the sustainability of harvesting corn stover.   Agron. J. 103:288-295.
  23. Franklin, Nancy, J. Humphrey, G.W. Roth, and D.G. Jackson.  2010.  A time of opportunity energy, Extension and economic development.  Journal of Higher Education Outreach and Engagement 14(3): 13-46.
  24. K. K. Grover, H. D. Karsten, and G. W. Roth. 2009. Corn Grain Yields and Yield Stability in Four Long-Term Cropping Systems. Agron. J. 101: 940–946.
  25. Roth, G.W and J. G. Lauer. 2008. Impact of Defoliation on Corn Forage Quality. Agron. J. 100: 651—657.
  26. Roth, G.W., D.B. Beegle, S.M. Heinbaugh, and M.E. Antle. 2006. Starter Fertilizers for Corn on Soils Testing High in Phosphorus in the Northeastern USA, Agron. J. 98: 1121–1127.
  27. Myers, M.W., W.S. Curran, M.J. Vangessel, Brad Majek, B.A. Scott, D.A. Mortensen, D.D. Calvin, H.D. Karsten, and G.W. Roth. 2005. The effect of weed density and application timing on weed control and corn grain yield. Weed Technology. 19:102–107.
  28. Myers, M.W., W.S. Curran, M.J. Vangessel, Brad Majek, D.A. Mortensen, D.D. Calvin, H.D. Karsten, and G.W. Roth. 2005. Effect of soil disturbance on annual weed emergence in the Northeastern United States. Weed Technology. 19:274–282.
  29. Dillehay, B.L., D.D. Calvin, G.W. Roth, J.A. Hyde, R.J. Kratochvil, J.M. Russo and D.G. Voight. 2005. Verification of a European Corn Borer (Lepidoptera Crambidae) loss equation in the major corn production region of the Northeastern United States. J. Econ. Entomol. 96(1): 103–112.
  30. Thomison, P.R., G. W. Roth, R. W. Elmore, and J.G. Lauer. 2004. A model for testing new seed technologies. Journal of Extension 42(4):
  31. Werner, E.L., W.S. Curran, J.K. Harper, G.W. Roth and D.P. Knievel. 2004. Velvetleaf (Abutilon theophrasti) interference and seed production in corn silage and grain. Weed Technology 18 (3): 779–783.
  32. Myers, M.W., W.S. Curran, M. J. Vangessel, D.D. Calvin, D.A. Mortensen, B.A. Majek, H.D. Karsten, and G. W. Roth. 2004. The effect of weed density and application timing on weed control and corn (Zea mays) grain yield. Weed Science 52:913–919.
  33. Dillehay, B.L, G.W. Roth, D. D. Calvin, G.L. Kuldau, J. Hyde and R. Kratochvil. 2004. Performance of Bt-corn hybrids, their near isolines and leading corn hybrids in Pennsylvania and Maryland Agron. J. 96(3):818–824
  34. Lauer, J.G., G. W. Roth and M. Bertram. 2004. Impact of defoliation on corn forage. Agron. J. 96: 1459–1463.
  35. Roth, G.W., D.B. Beegle, and M.E. Antle. 2003. Evaluation of starter fertilizers for corn on soils testing high for phosphorous. Comm. in Soil Sci. and Plant Anal. 34:1381–1392.
  36. Karsten, H. D., G. W. Roth, and L.D. Muller. 2003. Evaluation of corn hybrids at two stages of development for cattle grazing. Agronomy Journal. 95:870–877.
  37. Rotz, C.A., G.W. Roth, and W.L. Stout. 2002. Economic and environmental implications of small grain production and use on Pennsylvania dairy farms. Applied Engineering in Agriculture. Vol. 18(4): 417–428.
  38. Roth, G.W., J.K. Harper, A.A. Hower, and R.A. Kyper. 2002. Potential of Shorter Corn/Alfalfa Rotations for Dairy Farms. Journal of Sustainable Agriculture 20(2): 41–52.
  39. Esbenshade, W.R., W.S. Curran, G.W. Roth, N.L. Hartwig, and M. D. Orzolek. 2001. Effect of row spacing and herbicides on burcucumber (Sicyos angulatus) control in herbicide resistant corn (Zea mays). Weed Technology 15 (2): 348–354.
  40. Esbenshade, W.R., W.S. Curran, G.W. Roth, N.L. Hartwig, and M. D. Orzolek. 2001. Effect of tillage, row spacing, and herbicide on the emergence and control of burcucumber (Sicyos angulatus) in soybean (Glycine max). Weed Technology 15 (2):229–235.
  41. Esbenshade, W.R., W.S. Curran, G.W. Roth, N.L. Hartwig, and M. D. Orzolek. 2001. Effect of establishment date and crop competition on burcucumber fecundity. Weed Science 49(4): 524–527.
  42. Rotz, C. A. , G. W. Roth, K.J. Soder, and R. R. Schnabel. 2001. Economic and environmental implications of soybean production and use on Pennsylvania dairy farms. Agron. J. 93:418–428.
  43. Messersmith, D.T., W.S. Curran, G.W. Roth, N.L. Hartwig, M.D. Orzolek. 2000. Tillage and herbicides affect burcucumber management in corn. Agron. J. 92:181–185.
  44. Messersmith, D. T., W. S. Curran, N. L.Hartwig, M. D. Orzolek, and G. W. Roth. 1999. Evaluation of several herbicides for burcucumber (Sicyos angulatus) control in corn. Weed Technol. 13:520–524.
  45. Swartz, L., E. Chamberlain, D. Voight and G.W. Roth. 1999. Performance of Bt Corn hybrids in Pennsylvania and New Jersey. New Jersey Grain and Forage Journal 6:61–64
  46. Shoener, A., and G. W. Roth. 1999. Corn yield response to plant population in a high yield environment. New Jersey Grain and Forage Journal 6:12–15.34. 
  47. Roth, G.W. and J.O. Yocum. 1997. Use of hybrid growing degree day ratings for corn in the Northeast U.S. Journal of Prod. Ag. 10:283–288.
  48. Nandula,V., W. C. Curran and G. W. Roth. 1995. Effectiveness of nicosulfuron and primisulfuron on wirestem muhly (Muhlenbergia frondosa) control in no-till corn (Zea mays). Weed Tech. 9:331–338.
  49. Nandula, V., W. C. Curran , G. W. Roth and N.L Hartwig. 1995. Effectiveness of adjuvants with nicosulfuron and primisulfuron for wirestem muhly (Muhlenbergia frondosa) control in no-till corn (Zea mays). Weed Tech. 9:525–530.
  50. Roth G. W, S. Fathi, R. H. Fox, J. R. Rosenberger and W. P. Piekielek. 1995. Effect of harvest method and feed value on the economic optimum nitrogen rate for corn. Commun. Soil Sci. Plant Anal. 26(7&8):1009–1021.
  51. Roth, G. W., D. D. Calvin and S. M. Lueloff. 1995. Tillage, nitrogen timing and planting date effects on western corn rootworm injury to corn. Agron J. 87:189–193.
  52. Roth, G.W. 1994. Hybrid quality and yield differences for corn silage in Pennsylvania. Journal of Production Agriculture 7:50–54.
  53. Hartzler, R.W. and G.W. Roth. 1993 Effect of prior year's weed control on herbicide effectiveness in corn (Zea mays). Weed Technology 7:611–614.
  54. Ganoe, K.H. and G.W. Roth. 1992. Kernel milk line as an indicator of harvest timing for whole plant corn. Journal of Production Agriculture 5:519–523.
  55. Roth, G.W., D.B. Beegle and P.J. Bohn. 1992. Field evaluation of a pre-sidedress soil nitrate test and quicktest for corn in Pennsylvania. Journal of Production Agriculture 5:476–481.
  56. Roth, G.W., D.B. Beegle, R.H. Fox, J.D. Toth, and W.P. Piekielek. 1991. Evaluation of a quicktest kit to determine soil nitrate. Commun. Soil Sci. Plant Anal. 22(3&4):191–200.
  57. Roth, G.W. and R.H. Fox. 1990. Soil nitrate accumulations following corn fertilized at various N rates in Pennsylvania. J. Env. Qual. 19:243–248.
  58. Fox, R.H., G.W. Roth, W.P. Piekielek, and K.V. Iversen. 1989. Soil and tissue nitrate tests compared for predicting soil nitrogen availability to corn. Agron. J. 81:971-974.
  59. Roth, G.W., R.H. Fox, and H.G. Marshall. 1988. Plant tissue tests for predicting nitrogen fertilizer requirements of winter wheat. Agron. J. 81:502-507.
  60. Marshall, H.G., F.L. Kolb, and G.W. Roth. 1987. Effects of N fertilizer rate, seeding rate, and row spacing on semi-dwarf and conventional spring oats. Crop Sci. 27:572-575.
  61. Roth, G.W. and H.G. Marshall. 1987. Effects of timing of nitrogen fertilization and a fungicide on soft red winter wheat. Agron. J. 79:197-200.
  62. Roth, G.W., D.D. Wolf, and E.S. Hagood, Jr. 1985. Alfalfa establishment without tillage as influenced by insecticide and vegetation suppression. Grass and Forage Science 40:473-478.
  63. Roth, G.W., H.G. Marshall, O.E. Hatley, and R.R. Hill. 1984. Effect of management practices on grain yield, test weight, and lodging of soft red winter wheat. Agron. J. 76:379-383.