Guido Schnabel

Plant and Environmental Sciences Department, Public Service Activities

Office: 105 Collings St./220 BRC
Phone: 864-656-6705
Personal Website:


 Educational Background

Univ of Stuttgart, Hohenheim 1997

Justus Liebig Univ Giessen 1993

 Courses Taught

Plant Disease Diagnostics and Management Summer Course


Dr. Guido Schnabel is a plant pathologist at Clemson University with over 25 years of experience working with pathogens of fruit crops. He has an active research and extension program focused on management of diseases of small fruits and stone fruits. Together with his technician Karen, MS students, PhD students, and postdocs he publishes in highly ranked, peer-reviewed journals. Since 2019 he has been Associate Editor of the international journal 'Pesticide Biochemistry and Physiology' and in charge of all fungicide-related submissions. His research and extension activities were recognized with the APS Lee Hutchins Award for Excellence in Tree Fruit Research in 2011, The APS Excellence in Extension Award in 2015, the Clemson University Godley Snell Award for Excellence in Research and the Clemson University Centennial Professorship Award for years 2017/2018. His outreach efforts are best known for his regional fungicide resistance monitoring as well as the development of the MyIPM smartphone app.

 Research Interests

Integrated management of diseases affecting peach and strawberry. Dr. Schnabel studies molecular mechanisms of fungicide resistance in Colletotrichum, Monilinia, and Botrytis; monitors resistance in the field; and determines the efficacy of fungicides both in vitro and in field trials. He identifies and characterizes tree fruit pathogens and has also developed cultural management strategies of root diseases.

 Extension and Outreach

Extension programs include commercial grower education, county agent support, extension presentations, publications, on-farm visits, using technology for information transfer, identification of pathogen resistance, and farm-specific consultation to improve disease and resistance management.


Publications since 2014
Chechi, A., Stahlecker, J., Dowling, M. E. and G. Schnabel 2019. Diversity in species composition and fungicide resistance profiles in Colletotrichum isolates from apple. Pestic. Biochem Physiol. 158:18-24.

Hu, M-J., S. D. Cosseboom, and G. Schnabel 2019. AtrB-Associated Fludioxonil Resistance in Botrytis fragariae Not Linked to Mutations in Transcription Factor Mrr1. Phytopathology 109:839-846.

Froelich, M. and G. Schnabel. 2019. Investigation of fungi causing twig blight diseases on peach trees in South Carolina. Plant Dis. 103:705-710.

Dowling, ME, Bridges, WC, Cox, BM, Sroka, T, Wilson, JR, and Schnabel, G. 2019. Preservation of Monilinia fructicola genotype diversity within fungal cankers. Plant Dis. 103:526-530.

Allran, J., G. Schnabel, and J. C. Melgar 2019. Peach bagging in the southeastern U.S., J. AM. POMOL. SOC. 73:38-46.

Cheng, S., G. Schnabel, H. Yuan, C. Luo 2019. LAMP detection of the genetic element ‘Mona’ associated with DMI resistance in Monilinia fructicola. Pest Manag. Sci., 75: 779-786.

Cosseboom, S. D., K. L. Ivors, G. Schnabel, P. K. Bryson, and G. J. Holmes 2019. Within-season shift in fungicide resistance profiles of Botrytis cinerea in California strawberry fields. Plant Dis. 103:59-64.

Chen, S. Y. Wang, G. Schnabel, C. A. Peng, S. Lagishetty, K. Smith, C. X. Luo, and H. Yuan 2018. Inherent Resistance to 14?-Demethylation Inhibitor Fungicides in Colletotrichum truncatum Is Likely Linked to CYP51A and/or CYP51B Gene Variants. Phytopathology, 108:1263-1275.

Rivera, Y., K. Zeller, S. Srivastrava, J. Sutherland, M. Galvez, M. Nakhla, A. Poniatowska, G. Schnabel, G. Sundin, and Z. G. Abad 2018. Draft genome resources for the phytopathogenic fungi Monilinia fructicola, M. fructigena, M. polystroma and M. laxa, the causal agents of brown rot. Phytopathology 108:1141-1142.

Dowling, M. E., Hu, M-J., and G. Schnabel 2018. Fungicide resistance in Botrytis fragariae and species prevalence in the Mid-Atlantic United States. Plant Dis. 102:964-969.

Chen, F., Q Zhou, J. Xi, D.L. Li, G. Schnabel, and J. Zhan 2018. Analysis of RPA190 revealed multiple positively selected mutations associated with metalaxyl resistance in Phytophthora infestans. Pest Manag. Sci. 74:1916-1924.

Cosseboom, S.D., K. Ivors, G. Schnabel, and G. Holmes 2017. First Report of Botrytis mali causing gray mold on strawberry in California. Plant Dis. 102:679.

Rupp, S., C. Plesken, S. Rumsey, M. Dowling, G. Schnabel, R. Weber and M. Hahn 2017. Botrytis fragariae, a new species causing gray mold on strawberries, shows high frequencies of specific and efflux-based fungicide resistance. Applied and Environmental Microbiology. 83: 83:e00269- 17.

Cordova, L. G., L. V. Madden, A. Amiri, G. Schnabel, and N.A. Peres 2017. Meta-analysis of a web-based disease forecast system for control of anthracnose and botrytis fruit rots of strawberry in southeastern United States. Plant Dis. 101:1910-1917.

Hu, M.-J., M. E. Dowling, and G. Schnabel 2017. Genotypic and phenotypic variations in Botrytis spp. isolates from single strawberry flowers. Plant Dis. 102:179-184.

Dowling, M.E., M.-J. Hu, and G. Schnabel 2017. Identification and characterization of Botrytis fragariae isolates on strawberry in the United States. Plant Dis. 101:1769-1773.

Samarakoon, S. C., G. Schnabel, J. E. Faust, K. Bennett, J. Jent, M. J. Hu, S. Basnagala, and M. Williamson 2017. First report of resistance to multiple chemical classes of fungicides in Botrytis cinerea, the causal agent of gray mold from greenhouse-grown petunia in Florida. Plant Dis. 101:1052.

Hu, M-J., C. Peng, J.C. Melgar and G. Schnabel 2017. Investigation of potential causes of peach skin streaking. Plant Dis. 101:1601-1605.

Dowling, M.E., Schnabel, G., Boatwright, H.G., and S. Everhart 2017. Novel gene-sequence markers for isolate tracking within Monilinia fructicola lesions. Pest Manag. Sci. 73:1822-1829.

Dowling, M. E. and G. Schnabel 2017. First report of Botrytis mali causing gray mold on strawberry in the United States. Plant Dis. 101:1034.

Hao, X.J., Hu, M.J., Chen, S.N., and G. Schnabel 2017. Challenges in assessing efficacy of polyoxin-D zinc salt against Colletotrichum species. J. Plant Pathol. 99:513-516.

Rennberger, G., M. Dowling, A.P. Keinath and G. Schnabel 2017. First Report of Root Rot Caused by Pythium ultimum on Acanthosicyos horridus (Cucurbitaceae). Plant Dis. 101:258.

Chen, S. N., N. Yuan, G. Schnabel and C. X. Luo 2017. Function of the genetic element ‘Mona’ associated with fungicide resistance in Monilinia fructicola. Mol. Plant Pathol. 18:90-97.

Jie?Hui Song, Wei Wei, Bo Lv, Yang Lin, Wei?Xiao Yin, You?Liang Peng, Guido Schnabel, Jun?Bin Huang, Dao?Hong Jiang, Chao?Xi Luo 2016. Rice false smut fungus hijacks the rice nutrients supply by blocking and mimicking the fertilization of rice ovary. Environmental Microbiology 18:3840-3849.

Schnabel, G. 2016. Evolution, mechanisms and management of fungicide resistance in Botrytis cinerea. Acta Horticulturae, DOI 10.17660/ActaHortic.2016.1117.15.

Chen, S. N., C.X. Luo, M.J. Hu, and G. Schnabel 2016. Sensitivity of Colletotrichum species, including C. fioriniae and C. numphaeae, from peach to demethylation inhibitor fungicides. Plant Dis. 100:2434-2441.

Hu, M.J., K. D. Cox, and G. Schnabel 2016. Resistance to increasing chemical classes of fungicides by virtue of ‘Selection by Association’ in Botrytis cinerea. Phytopathology 106:1513-1520.

Dowling, M. E., P. K. Bryson, H. G. Boatwright, J. R. Wilson, Z. Fan, S. E. Everhart, P. M. Brannen, and G. Schnabel 2016. Effect of fungicide applications on Monilinia fructicola population diversity and transposon movement. Phytopathology 106:1504-1512.

Dowling, M. E., Hu, M. J., Schmitz, L. T., Wilson, J. R., and G. Schnabel 2016. Characterization of Botrytis cinerea isolates from strawberry with reduced sensitivity to polyoxin D Zinc Salt. Plant Dis. 100:2057-2061.

Chen, S. N., C. X. Luo, M. J. Hu, and G. Schnabel 2016. Fitness and competitive ability of Botrytis cinerea isolates with resistance to multiple chemical classes of fungicides. Phytopathology 106:997-1005.

Dowling, M. E, G. Schnabel, M. Williamson, R. S. Sekhon and K. J. Zielinski 2016. First report of sorghum anthracnose caused by Colletotrichum sublineola in South Carolina. Plant Dis. 100:1236.

Ishii, H., F. Zhen, M. Hu, X. Li, and G. Schnabel 2016. Efficacy of SDHI fungicides, including benzovindi?upyr, against Colletotrichum species. Pest Manag. Sci. 72:1844-1853.

Mair, W., Lopez-Ruiz, F., Stammler, G., Clark, W., Burnett, F., Hollomon, D., Ishii, H., Thind, T. S., Brown, J., Fraaije, B., Cools, H., Shaw, M., Fillinger, S., Walker, A. S., Mellado, E., Schnabel, G., Mehl, A., and R. P. Olivera 2016. Proposal for a unified nomenclature for target-site mutations associated with resistance to fungicides. Pest Manag. Sci. 72:1449-1459.

Montone, V. O., C. W. Fraisse, N. A. Peres, P. C. Sentelhas, M. Gleason, M. Ellis, and G. Schnabel 2016. Evaluation of leaf wetness duration models for operational use in strawberry disease-warning systems in four US states. Int. J. Biometeorol. DOI 10.1007/s00484-016-1165-4.

Hu, M., Fernández-Ortuño, D., and G. Schnabel 2016. Monitoring resistance to SDHI fungicides in Botrytis cinerea from strawberry fields. Plant Dis. 100:959-965.

Chen, F., Everhart, S. E., Bryson, P. K., Luo, C. L., Song, X., Liu, X., and G. Schnabel 2015. Fungicide-induced transposon movement in Monilinia fructicola. Fung. Genet. Biol. 85:38-44.

Dowling, M. E., Schnabel, G., and M. Williamson 2015. First Report of Powdery Mildew Caused by Golovinomyces orontii (Erisyphe orontii) on Vinca major in South Carolina. Plant Dis. 100:218.

Yin, L. F., Chen, S. N., Chen, G. K., Schnabel, G., Du, S. F., Chen, C., Li, G. Q., and C. X. Luo 2015. Identification and characterization of three Monilinia species from plum in China. Plant Dis. 99:1775-1783.

Fan, Z., J. H. Yang, F. Fan, C. X. Luo, and G. Schnabel 2015. Fitness and competitive ability of Alternaria alternata field isolates with resistance to SDHI, QoI, and MBC fungicides. Plant Dis. 99:1744-1750.

Lehner, M. S., Paula Junior, T. J., Silva, R. A., Vieira, R. F., Carneiro, J. E. S., Schnabel, G., and E. S. G. Mizubuti 2015. Fungicide sensitivity of Sclerotinia sclerotiorum: A thorough assessment using discriminatory dose, EC50, high-resolution melting analysis, and description of new point mutation associated with thiophanate-methyl resistance. Plant Dis. 99:1537-1543.

Hu, M. J., A. Grabke, and G. Schnabel 2015. Investigation of the Colletotrichum species complex causing peach anthracnose in South Carolina. Plant Dis. 99:797-805.

Hu, M. J., A. Grabke, M. E. Dowling, H. Holstein, and G. Schnabel 2015. Resistance in Colletotrichum siamense from peach and blueberry to thiophanate-methyl and azoxystrobin. Plant Dis. 99:806-814.

Fernández-Ortuño, D., A. Grabke, X. Li and G. Schnabel 2014. Independent emergence of resistance to seven chemical classes of fungicides in Botrytis cinerea. Phytopathology 105:424-432.

Yang, J. H., P. M. Brannen, and G. Schnabel 2015. Resistance in Alternaria alternata to SDHI fungicides causes rare disease outbreak in peach orchards. Plant Dis. 99:65-70.

Chen, S. N., Y. Shang, Y. Wang, G. Schnabel, Y. Lin, L. F. Yin, and C. X. Luo 2014. Sensitivity of Monilinia fructicola from Peach Farms in China to Four Fungicides and Characterization of Isolates Resistant to Carbendazim and Azoxystrobin. Plant Dis. 98:1555-1560.-80

Grabke, A., D. Fernández-Ortuño, A. Amiri, X. Li, N. Peres, P. Smith and G. Schnabel 2014. Characterization of iprodione resistance in Botrytis cinerea from strawberry and blackberry. Phytopathology. 104:396-402.

Li, X.P., Fernández-Ortuño, D., S. Chen, A. Grabke, C. X. Luo, W. C. Bridges, and G. Schnabel 2014. Location-specific fungicide resistance profiles and evidence for stepwise accumulation of resistance in Botrytis cinerea. Plant Dis. 98:1066-1074. EDITORS PICK, APS, September, 2014

Fernández-Ortuño, D., P. K. Bryson, G. Schnabel 2014. First report of Pilidium concavum causing tan-brown rot on strawberry nursery stock in South Carolina. Plant Dis. 98:1010.

Grabke, A., M. Williamson, G. W. Henderson, and G. Schnabel 2014. First report of anthracnose on peach fruit caused by Colletotrichum truncatum in South Carolina. Plant Dis. 98:1154.

Li, X.P., Fernández-Ortuño, D., Grabke, and G. Schnabel 2014. Resistance to fludioxonil in Botrytis cinerea isolates from blackberry and strawberry. Phytopathology. 104:724-732.

Fernández-Ortuño, D., A. Grabke, P. K. Bryson, E. D. Beasley, L. A. Fall, P. M. Brannen and G. Schnabel 2014. First report of fludioxonil resistance in Botrytis cinerea from a blackberry field in Georgia. Plant Dis. 98:848.

Fernández-Ortuño, D., A. Grabke, P. K. Bryson, A. Amiri, X. Li, N. Peres, and G. Schnabel 2014. Fungicide resistance profiles in Botrytis cinerea from strawberry fields of seven southern U.S. States. Plant Dis. 98:825-833.

Fernández-Ortuño, D., A. Grabke, P. K. Bryson, R. J. Rouse, P. Rollins and G. Schnabel 2014. First report of fludioxonil resistance in Botrytis cinerea, the causal organism of gray mold, from strawberry fields in Maryland and South Carolina. Plant Dis. 98:692.

Yin, L.F., Wang, F., Zhang, Y., Kuang, H., Schnabel, G., Li, G.Q., and C. X. Luo 2014. Evolutionary analysis revealed the horizontal transfer of the Cyt b gene from fungi to chromista. Molecular Phylogenetics and Evolution. 76:155-161.


Professional Website