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Barbara Shew

Research Assistant Professor Emeritus

Management of ornamental and peanut diseases

Gardner Hall 3404



  • Ella Reeves, M.S. Fall 2020, Co-advised with Jim Kerns. Thesis title: Pythium spp. associated with root rot and stunting of winter crops in North Carolina.
  • Alejandro Llanos Melo, M.S. 2020, Co-advised with Sara Villani. Thesis title: Evaluation of SDHI fungicides and host plant defense inducers for the management of plant pathogens in two different cropping systems.
  • Emma Lookabaugh, Ph.D. 2017. Dissertation title:  Integrated strategies for managing Pythium root rot and fungicide-insensitive strains of Pythium aphanidermatum in poinsettia. Current position: Technical Services, turf and ornamentals, BASF
  • Michael Cannon, M.S. 2017. Thesis title: Sensitivity of Sclerotinia minor to common peanut fungicides
  • Emma Lookabaugh, M.S. 2013. Thesis title: Understanding the impact of Pythium species on floricultural crops in North Carolina. Current position: Technical Services, turf and ornamentals, BASF
  • Sarah Rurak, M.S. 2009. Thesis title: Evaluation of biological and other novel seed and soil treatments for organic peanut production. Current position: Ph.D. student, Cornell University
  • Damon Smith, Ph.D. 2007, M.S., 2004. Thesis title: Biology and Epidemiology of Sclerotinia minor on Peanut (Arachis hypogaea L.). Current position: Assistant Professor, University of Wisconsin
  • Laura Duffie, M.S. 2003. Effects of intercropping corn and peanut on peanut leaf spot management and the spatial and temporal epidemiology of Cercospora arachidicola. Current position: USDA-APHIS


Pythium root rot

Our objective is to better understand how Pythium infections contribute to poor stands, stunting, and death of North Carolina’s winter-grown crops, including clary sage, winter wheat, and selected cover crop species. This work has involved widespread sampling from these hosts across the state, isolation and identification of the Pythium species infecting them, pathogenicity testing, and characterization of interactions between Pythium and environmental variables on selected hosts species.

North Carolina is a major producer of floricultural crops and Pythium is frequently diagnosed on floricultural samples submitted to the Plant Disease and Insect Clinic (PDIC). Greenhouses in North Carolina previously had not been systematically sampled for the presence of Pythium. The severity of the problem, the Pythium species involved, and the extent of mefenoxam resistance in greenhouse populations were unknown. To address these questions, graduate student Emma Lookabaugh collected herbaceous ornamentals exhibiting symptoms of Pythium root rot from 18 greenhouses in 14 counties in North Carolina. Isolates were identified to species by sequencing of the ITS rDNA region. More than half of the 277 isolates collected were resistant to mefenoxam. Resistant and sensitive strains were found within the same greenhouse and species. We plan to use the results of this research to provide mefanoxam resistance screening services to growers through the Plant Disease and Insect Clinic.

Peanut diseases

Peanuts are grown on about 90,000 acres in North Carolina. The crop is affected by several serious diseases, including leaf spots, southern stem rot, Sclerotinia blight, Cylindrocladium black rot, and Spotted wilt. My research aims to develop integrated disease management tactics that take advantage of host resistance and weather-based disease advisories to minimize the use of fungicides and other pesticides in peanut production. Currently, I am focusing on developing reduced input disease control methods that can be used on the new partially resistant cultivars Bailey, Sugg, Sullivan and Wynne. I work with peanut breeder Dr. Tom Isleib in evaluation of disease resistance in new breeding lines. I also work with Dr. David Jordan to understand the impacts of cultural practices on disease development and crop health.

Extension & Outreach

Plant Disease and Insect Clinic

I served as the Director of the Plant Disease and Insect Clinic at NCSU from 2009 – 2019. The clinic is staffed with two full-time plant disease diagnosticians, Shawn Butler and Mike Munster, and full-time entomologist, Matt Bertone. Graduate student Emma Lookabaugh diagnoses diseases of tomatoes and other crops. The clinic provides diagnostic training for County Agents and Master Gardeners and uses social media (Facebook, Twitter, and Blog) for outreach to a wide audience of Extension personnel, farmers, nurseries, and homeowners.


As part of a team that includes Dr. David Jordan in Crop Science, entomologist Dr. Rick Brandenburg, and county extension personnel, I have extension responsibilities for peanut diseases. We prepare educational materials, conduct field testing, and participate in grower meetings, demonstrations and field days. In addition, in cooperation with the North Carolina State Climate office, I provide daily peanut disease advisories for peanut growers in North Carolina.

Peanut Portal – Comprehensive website for peanut information and updates
Peanut Information – Peanut production guide
Agricultural Chemicals Manual
Peanut Risk Management – See how production practices affect pest problems
Peanut Disease Photos
Peanut Disease Advisories – Click on this link to view today’s weather based disease advisories and for information on how to interpret advisories. You may contact Dr. Shew to receive daily advisory emails.
Peanut Scouting Manual – IPM Center

Selected Publications
  • Lookabaugh, E.C.  Whipker, B., and Shew, B. B. 2017. Evaluation of Poinsettia Cultivars for Resistance to Pythium Root Rot Caused by Pythium aphanidermatum. HortTechnology doi: 10.21273/HORTTECH03817-17.
  • E. C. Lookabaugh, A. Thomas, B. B. Shew, S. C. Butler, and F. J. Louws. 2017. First Report of Black Leaf Mold of Tomato Caused by Pseudocercospora fuligena in North Carolina. Plant Disease
  • Lookabaugh, E., Shew, B., and Cowger, C. 2017. Three Pythium species isolated from severely stunted wheat during an outbreak in North Carolina. Plant Health Progress 18:169-173.
  • B.R. Lassiter, G.G. Wilkerson, D.L. Jordan,* G.S. Buol, B.B. Shew, R. Brandenburg,
    A. Herbert Jr., and P. Phipps. 2017. Development and Deployment of a Composite Pest Risk
    Assessment Decision Support System for Peanut (Arachis hypogaea L.) in the Virginia-Carolina Region. Crop Forage Turfgrass Manage. doi:10.2134/cftm2017.08.0054
  • A. M. Koehler, E. C. Lookabaugh, B. B. Shew, and H. D. Shew. 2017. First Report of Pythium Root Rot of Stevia Caused by Pythium myriotylumP. irregulare, and P. aphanidermatum in North Carolina. Plant Disease 101:1331.
  • Junsopa, C., Jogloy, S, Saksirirat, W, Songsri, P, Kesmala, T, and Shew, B.B. 2017. Genotypic diversity of Jerusalem artichoke for resistance to stem rot caused by Sclerotium rolfsii under field conditions. Euphytica 213:164.
  • Jordan, D.L., Corbett, T., Bogle, C., Shew, B., Brandenburg, R. and Ye, W. 2017.  Effect of previous rotation on plant parasitic nematode population in peanut and Crop Yield. Crop Management doi:10.2134/cftm2016.12.0086
  • Junsopa, C., Jogloy, S., Saksirirat, W., Songsri, P, Kesmala, T., Pathanothai, A., Shew, B.B. 2016.  Inoculation with Sclerotium rolfsii, cause of stem rot in Jerusalem artichoke, under field conditions. Eur. J. Plant Pathology Doi 10.1007/s/0658-016-089-1
  • Boudreau, M.A., B. B. Shew, and L.E. Duffie. 2015. Impact of intercropping on epidemics of groundnut leaf spots: defining constraints and opportunities through a 7-year field study. Plant Pathology Doi 10.1111/ppa.12440.
  • Lookabaugh, E.C., Ivors, K.M., Shew, B.B. 2015. Mefenoxam sensitivity, aggressiveness, and identification of Pythium species causing root rot on floriculture crops in North Carolina. Plant Disease 99:1550-1558.
  • Isleib, T.G., Milla-Lewis, S.R., Pattee, H.E., Copeland, S.C., Zuleta, M.C., Shew, B.B., Hollowell, Sanders, T.H., Dean, L.O. Hendrix, K.W., Balota, M., Chapin, J.W., and Monfort, W.S. 2015. Registration of ‘Sugg’ Peanut. J. Crop Regist. 9:44-52
  • Jordan, D.L., P. D. Johnson, T. Corbett, J. Schultheis, B. Shew, R. Brandenburg, W. Ye. 2014. Peanut response to crop rotations including clary sage, snap bean, and sweet potato. Crop Manag. doi:10.2134/CM-2014-0038-RS
  • Drake, W.L., D. L. Jordan, P. D. Johnson, B. B. Shew, R. L. Brandenburg, T. Corbett. 2014. Peanut response to planting date, tillage, and cultivar in North Carolina. Agronomy Journal 106: 486-490
  • Isleib, T.G., B.B. Shew, S.R. Milla-Lewis, W.B. Dong, S.C. Copeland, C. Arellano. 2013. Stability analysis of incidence of tomato spotted wilt in virginia-type peanut cultivars and breeding lines. Peanut Sci. 40:24-30.
  • Chahal, G.S., D.L. Jordan, B.B. Shew, R.L. Brandenburg, J.D. Burton, and D. Danehower. 2012. Interactions of Agrochemicals Applied to Peanut; Part 2: Effects on Fungicides. Crop Protection
  • Partridge-Telenko, D.E., J. Hu, D. M. Livingstone, B. B. Shew, P. M. Phipps, and E. A. Grabau. 2011. Sclerotinia Blight Resistance in Virginia-Type Peanut Transformed with a Barley Oxalate Oxidase Gene. Phytopathology 101: 786-793.
  • Ruark, S.J., and Shew, B.B. 2010. Evaluation of microbial, botanical, and organic treatments for control of peanut seedling diseases. Plant Dis. 84:445‐454.

Selected Technical Reports 

  • Shew, B.B. 2015. Response of peanut diseases in North Carolina to spray programs with labeled fungicides, 2014. Plant Dis. Mgt. Rep. 9
  • Shew, B.B. 2015. Response of peanut diseases in North Carolina to in-furrow inoculation and fungicide applications, 2014. Plant Dis. Mgt. Rep. 9
  • Shew, B.B.  2014. Evaluation of Abound, Convoy, and Folicur for stem rot control on stevia in North Carolina, 2014. Plant Dis. Mgt. Rep. 9
  • Shew, B.B. 2013.  Evaluation of experimental fungicides for peanut disease control in North Carolina, 2013. Plant Dis. Mgt. Rep. 8
  • Shew, B.B. 2011. Evaluation of Abound plus Alto for control of peanut diseases in North Carolina, 2011. Plant Dis. Mgt. Rep. 6
  • Shew, B.B. 2011. Evaluation of Fontelis and Topguard for control of peanut diseases in North Carolina, 2011. Plant Dis. Mgt. Rep. 6
  • Shew, B.B. 2011. Evaluation of spray programs with labeled fungicides for the control of peanut diseases in North Carolina, 2012.     Plant Dis. Mgt. Rep. 6
  • Shew, B.B., B.B. 2010. Evaluation of Topguard and other fungicides for the control of peanut diseases in North Carolina, 2009. Plant Dis. Mgt. Rep. 4
  • Shew, B.B., B.B. 2010. Evaluation of in-furrow and foliar fungicides for control of peanut diseases in North Carolina, 2009. Plant Dis. Mgt. Rep. 4


B.S, Plant Pathology, Colorado State University (1976)
M.S, Plant Pathology, North Carolina State University (1980)
Ph.D, Plant Pathology, North Carolina State University (1983)