Professor of Plant Pathology
Research and Extension Vegetable Pathologist
Horticulture Program Team, Plant and Environmental Sciences Department, Coastal Research and Education Center
Office: Coastal REC, Charleston, SC
Ph.D. Plant Pathology
Cornell University 1988
M.S. Plant Pathology
Cornell University 1985
Michigan State University 1982
I am the state vegetable pathologist for South Carolina with a faculty appointment of 80% research and 20% Extension. The focus of my program is sustainable disease management for vegetable crops. My area of expertise is diseases of cucurbits. Six M.Sc. and four Ph.D. students have graduated under my direction. I was the lead editor of the Compendium of Cucurbit Diseases and Pests, 2nd edition, APS Press, published 2017. In 2018 I received the Godley-Snell Award for Excellence in Agricultural Research from Clemson University. In 2020 I received the Outstanding Plant Pathologist Award from the American Phytopathological Society--Southern Division. In 2023 I received one of the inaugural Outstanding Specialist awards from the South Carolina Association of County Agricultural Agents.
My research focuses on sustainable disease management for vegetables, including the management, ecology, and epidemiology of fungi, oomycetes (water molds), and other plant pathogens. My area of expertise is Stagonosporopsis citrulli (formerly Didymella bryoniae), the fungus that causes gummy stem blight on cucurbits. Crops studied include the cucurbits watermelon, muskmelon, cucumber, and zucchini; the fruiting vegetables eggplant, pepper, and tomato; the leafy brassicas kale, collard, and mustard; and beets. Successful management strategies should be effective, economical, and environmentally responsible.
Current research projects include resistance to fungicides in fungal pathogens; fungicide efficacy against gummy stem blight on watermelon and downy mildew on cucumber and squash; ecology and management of Pythium spp. on vegetables; management of Cercospora leaf spot on beet; management of anthracnose fruit rot on peppers; management of Phomopsis fruit rot on eggplant.
Extension and Outreach
The goal of my Extension program is to help people solve problems with their plants. The primary audience is small and large vegetable growers in South Carolina. Urban plant problems in the greater Charleston area also are addressed.
My Extension outreach includes grower, agent, Master Gardener, and home gardener education; vegetable disease management recommendations for conventional and organic growers; and vegetable disease diagnosis. I contribute yearly to the Southeastern U.S. Vegetable Crop Handbook. Since 2014 I am a tri-weekly gardening columnist for The Post and Courier newspaper, Charleston, SC.
1. Keinath, A. P., Rennberger, G., and Wechter, W. P. 2023. Widespread resistance to tebuconazole and cross-resistance to other DMI fungicides in Stagonosporopsis citrulli Isolated from watermelon in South Carolina. Plant Dis. 107: (published online 06/13/2023).
2. Keinath, A. P. 2023. Congruent and differential responses of Pseudoperonospora cubensis clades 1 and 2 to downy mildew fungicides. Plant Health Progress 24: (published online 04/05/2023).
3. Keinath, A. P., and Hajihassani, A. 2023. Grafting tomato to manage southern blight, prevent yield loss, and increase crop value. Plant Dis. 107: (published online 03/14/2023).
4. Keinath, A. P., Colburn, G. C., and Yang, X. 2023. Differential susceptibility of two Citrullus amarus pollenizer watermelons to five species of Pythium and Globisporangium. Plant Dis. 107: (published online 02/12/2023).
5. Keinath, A. P. 2023. Eggplant fruit periderm firmness correlated with resistance to Phytophthora nicotianae. Plant Health Prog. 24: (published online 12/05/2022).
6. Toporek, S. M., Branham, S. E., Keinath, A. P., and Wechter, W. P. 2023. QTL mapping of resistance to Pseudoperonospora cubensis Clade 2, mating type A1, in Cucumis melo and dual-clade marker development. Theoret. Appl. Genet. 136:91.
7. Kikway, I., Keinath, A. P., and Ojiambo, P. S. 2023. Within-season shift in fungicide sensitivity profiles of Pseudoperonospora cubensis populations in response to chemical control. Plant Dis. 107:1377-1385.
8. Keinath, A. P. 2022. Reduced sensitivity of Pseudoperonospora cubensis clades 1 and 2 to oxathiapiprolin in South Carolina. Plant Health Prog. 23(3):256-259.
9. Kikway, I., Keinath, A. P., and Ojiambo, P. S. 2022. Field occurrence and overwintering of oospores of Pseudoperonospora cubensis in the Southeastern United States. Phytopathology 112(9):1946-1955.
10. Toporek, S. M., and Keinath, A. P. 2022. Efficacy of fungicides used to manage downy mildew in cucumber assessed with multiple meta-analysis techniques. Phytopathology 112(8):1651-1658.
11. Kikway, I., Keinath, A. P., and Ojiambo, P. S. 2022. Temporal dynamics and severity of cucurbit downy mildew epidemics as affected by chemical control and cucurbit host type. Plant Dis. 106(3):1009-1019.
12. Keinath, A. P., and Silva, F. 2022. Economic impacts of reduced fungicide efficacy against downy mildew on slicing cucumber. Crop Protection 155:105934.
13. Keinath, A. P. 2022. Differences in susceptibility to Phomopsis blight of seven eggplant cultivars with different fruit types. Plant Health Progress 23(1):57-64.
14. Rennberger, G., Turechek, W. W., and Keinath, A. P. 2021. Dynamics of the ascospore dispersal of Stagonosporopsis citrulli, a causal agent of gummy stem blight of cucurbits. Plant Pathol. 70:1908-1919.
15. Toporek, S. M., Branham, S. E., Katawczik, M. M., Keinath, A. P., and Wechter, W. P. 2021. QTL mapping of resistance to Pseudoperonospora cubensis clade 1, mating type A2, in Cucumis melo. Theoret. Appl. Genet. 134:2577-2586.
16. Keinath, A. P. 2021. Premix fungicides that reduce development of fruiting bodies but not leaf lesions by Stagonosporopsis citrulli on watermelon leaves in the field. Plant Dis. 105(5):1415-1421.
17. Hudson, O., Waliullah, S., Fulton, J. C., Ji, P., Dufault, N. S., Keinath, A., and Ali, M. E. 2021. Marker development for differentiation of Fusarium oxysporum f. sp. niveum race 3 from races 1 and 2. Int. J. Molec. Sci. 22:822.
18. Toporek, S. M., and Keinath, A. P. 2020. Evaluating cucurbit rootstocks to prevent disease caused by Pythium aphanidermatum and P. myriotylum on watermelon. Plant Dis. 104(11):3019-3025.
19. Toporek, S. M., and Keinath, A. P. 2020. Characterization of Pythium species collected from a multiple time-point sampling of cucurbits in South Carolina. Plant Dis. 104(11):2832-2842.
20. Keinath, A. P., DuBose, V. B., Katawczik, M. M., and Wechter, W. P. 2020. Identifying races of Fusarium oxysporum f. sp. niveum in South Carolina recovered from watermelon seedlings, plants, and field soil. Plant Dis. 104(9):2481-2488.
21. Rennberger, G., and Keinath, A. P. 2020. Stachybotriaceae on cucurbits demystified: Genetic diversity and pathogenicity of ink spot pathogens. Plant Dis. 104:2242-2251.
22. Keinath, A. P. 2019. Integrated management of downy mildew on slicing cucumber with fungicides and host resistance but not trellising. Plant Dis. 103:2592-2598.
23. Keinath, A. P., Miller, S. A., and Smart, C. D. 2019. Response of Pseudoperonospora cubensis to preventative fungicide applications varies by state and year. Plant Health Prog. 20:142-146.
24. Keinath, A. P., Wechter, W. P., Rutter, W. B., and Agudelo, P. A. 2019. Cucurbit rootstocks resistant to Fusarium oxysporum f. sp. niveum remain resistant when co-infected by Meloidogyne incognita in the field. Plant Dis. 103:1383-1390.
25. Rennberger, G., Gerard, P., and Keinath, A. P. 2019. Factors influencing the occurrence of foliar pathogens in commercial watermelon fields in South Carolina based on stratified cluster sampling. Plant Dis. 103:484-494.
26. Keinath, A. P., Coolong, T. W., Lanier, J. D., and Ji, P. 2019. Managing Fusarium wilt of watermelon with delayed transplanting and cultivar resistance. Plant Dis. 103:44-50.
27. Rennberger, G., Gerard, P., and Keinath, A. P. 2018. Occurrence of foliar pathogens of watermelon on commercial farms in South Carolina estimated with stratified cluster sampling. Plant Dis. 102:2285-2295.
28. Keinath, A. P., and Agudelo, P. A. 2018. Retention of resistance to Fusarium oxysporum f. sp. niveum in cucurbit rootstocks infected by Meloidogyne incognita. Plant Dis. 102:1820-1827.
29. Rennberger, G., and Keinath, A. P. 2018. Susceptibility of fourteen new cucurbit species to gummy stem blight caused by Stagonosporopsis citrulli under field conditions. Plant Dis. 102:1365-1375.
30. Neufeld, K. N., Keinath, A. P., and Ojiambo, P. S. 2018. Evaluation of a model for predicting the daily infection risk of squash and cantaloupe by Pseudoperonospora cubensis. Plant Dis. 102:855-862.
31. Keinath, A. P. 2018. Minimizing yield and quality losses in watermelon with multi-site and strobilurin fungicides effective against foliar and fruit anthracnose. Crop Prot. 106:72-78.
32. Neufeld, K. N., Keinath, A. P., Gugino, B. K., McGrath, M. T., Sikora, E. J., Miller, S. A., Ivey, M. L., Langston, D. B., Dutta, B., Keever, T., Sims, A., and Ojiambo, P. S. 2018. Predicting the risk of cucurbit downy mildew in the eastern United States using an integrated aerobiological model. Int. J. Biometeorol. 62:655-668.
33. Keinath, A. P., and DuBose, V. B. 2017. Disinfectant treatments that reduce transmission of Stagonosporopsis citrulli during cucurbit grafting. Plant Dis. 101:1895-1902.
34. Keinath, A. P., and DuBose, V. B. 2017. Management of southern blight on tomato with SDHI fungicides. Crop Prot. 101:29-34.
35. Neufeld, K. N., Keinath, A. P., and Ojiambo, P. S. 2017. A model to predict the risk of infection of cucumber by Pseudoperonospora cubensis. Microb. Risk Anal. 6:21-30.
36. Rennberger, G., Keinath, A. P., and Hess, M. 2017. Correlation of trichome density and length and polyphenol fluorescence with susceptibility of five cucurbits to Didymella bryoniae. J. Plant Dis. Prot. 124:313-318.
37. Sui, X., Zheng, Y., Li, R., Padmanabhan, C., Tian, T., Groth-Helms, D., Keinath, A. P., Fei, Z., Wu, Z., and Ling, K.-S. 2017. Molecular and biological characterization of Tomato mottle mosaic virus and development of RT-PCR detection. Plant Dis. 101:704-711.
38. Wechter, W. P., McMillan, M. M., Keinath, A. P., Smith, J. P., and Farnham, M. W. 2016. ‘Carolina Broadleaf’ mustard green (Brassica juncea) resistant to the bacterial leaf blight pathogen Pseudomonas cannabina pv. alisalensis. HortScience 51:1062-1064.
39. Keinath, A. P., Wechter, W. P., and Farnham, M. W. 2016. Suppression of bacterial blight on mustard greens with host plant resistance and acibenzolar-S-methyl. Plant Dis. 100:1921-1926.
40. Keinath, A. P. 2016. Polyoxin D and other biopesticides reduce gummy stem blight but not anthracnose on melon seedlings. Plant Health Prog. 17:177-181.
41. Keinath, A. P. 2016. Utility of a cucumber plant bioassay to assess fungicide efficacy in Pseudoperonospora cubensis. Plant Dis. 100:490-499.
42. Keinath, A. P. 2015. Efficacy of fungicides against powdery mildew on watermelon caused by Podosphaera xanthii. Crop Prot. 75:70-76.
43. Keinath, A. P. 2015. Baseline sensitivity of Didymella bryoniae to cyprodinil and fludioxonil and field efficacy of these fungicides against isolates resistant to pyraclostrobin and boscalid. Plant Dis. 99:815-822.
44. Keinath, A. P. 2014. Reproduction of Didymella bryoniae on nine species of cucurbits under field conditions. Plant Dis. 98:1379-1386.
45. Keinath, A. P., and Hassell, R. L. 2014. Suppression of Fusarium wilt caused by Fusarium oxysporum f. sp. niveum race 2 on grafted triploid watermelon. Plant Dis. 98:1326-1332.
46. Keinath, A. P., and Hassell, R. L. 2014. Control of Fusarium wilt of watermelon by grafting onto bottlegourd or interspecific hybrid squash despite colonization of rootstocks by Fusarium. Plant Dis. 98:255-266.
47. Keinath, A. P. 2014. Differential susceptibility of nine cucurbit species to the foliar blight and crown canker phases of gummy stem blight. Plant Dis. 98:247-254.
48. Ling, K.-S., Levi, A., Adkins, S., Kousik, C. S., Miller, G., Hassell, R., and Keinath, A. 2013. Development and field evaluation of multiple virus-resistant bottle gourd (Lagenaria siceraria). Plant Dis. 97:1057-1062.
49. Keinath, A. P. 2013. Susceptibility of cucurbit rootstocks to Didymella bryoniae and control of gummy stem blight on grafted watermelon seedlings with fungicides. Plant Dis. 97:1018-1024.
50. Keinath, A. P., and Hansen, Z. R. 2013. Isolates of Didymella bryoniae from South Carolina remain sensitive to DMI fungicides despite multi-year exposure. J. Phytopathol. 161:315-323.
51. Hansen, Z. R., and Keinath, A. P. 2013. Increased pepper yields following incorporation of biofumigation cover crops and the effects on soilborne pathogen populations and pepper diseases. Appl. Soil Ecol. 63:67-77.
52. Wechter, W. P., Keinath, A. P., McMillan, M., Smith, J. P., and Farnham, M. W. 2013. Expression of bacterial blight resistance in Brassica leafy greens under field conditions and inheritance of resistance in a Brassica juncea source. Plant Dis. 97:131-137.
53. Keinath, A. P., and DuBose, V. B. 2012. Controlling powdery mildew on cucurbit rootstock seedlings in the greenhouse with fungicides and biofungicides. Crop Prot. 42:338-344.
54. Keinath, A. P. 2012. Differential sensitivity to boscalid in conidia and ascospores of Didymella bryoniae and frequency of boscalid-insensitive isolates in South Carolina. Plant Dis. 96:228-234.
55. Keinath, A. P., and Kousik, C.S. 2011. Sensitivity of isolates of Phytophthora capsici from the eastern United States to fluopicolide. Plant Dis. 95:1414-1419.
56. Farnham, M. W., Keinath, A. P., and Grusak, M. A. 2011. Mineral concentration of broccoli florets in relation to year of cultivar release. Crop Sci. 51:2721-2727.
57. Ling, K.-S., Wechter, W. P., Walcott, R. R., and Keinath, A. P. 2011. Development of a real-time RT-PCR assay for Squash mosaic virus useful for broad spectrum detection of various serotypes and its incorporation into a multiplex seed health assay. J. Phytopathol. 159:649-656.
58. Levi, A., Thies, J. A., Simmons, A. M., Harrison, H., Hassell, R., and Keinath, A. 2011. USVL-220, a novel watermelon breeding line. HortScience 46:135–138.
59. Ling, K.-S., Wechter, W. P., Somai, B. M., Walcott, R. R., and Keinath, A. P. 2010. An improved real-time PCR system for broad-spectrum detection of Didymella bryoniae, the causal agent of gummy stem blight of cucurbits. Seed Sci. Technol. 38:692-703.
60. Keinath, A. P., Hassell, R. L., Everts, K. L., and Zhou, X.-G. 2010. Cover crops of hybrid common vetch reduce Fusarium wilt of seedless watermelon in the eastern United States. Plant Health Progress.
61. Keinath, A. P. 2010. Potassium phosphite mixed with other fungicides reduces yield loss to downy mildew on collard. Plant Health Progress.
62. Njoroge, S. M.C., Toler, J.E. and Keinath, A.P. 2010. Soil solarization on populations of Pythium spp., fluorescent Pseudomonas, and damping-off of broccoli and cucumber. Int. J. Veg. Sci. 16:15-31.
63. Keinath, A. P. 2009. Sensitivity to azoxystrobin in Didymella bryoniae isolates collected before and after field use of strobilurin fungicides. Pest Manag. Sci. 65:1090–1096.
64. Ha, Y., Fessehaie, A., Ling, K. S., Wechter, W. P., Keinath, A. P., and Walcott R. R. 2009. Simultaneous detection of Acidovorax avenae subsp. citrulli and Didymella bryoniae in cucurbit seedlots using magnetic capture hybridization and real-time polymerase chain reaction. Phytopathology 99:666-678.
65. Keinath, A. P. 2008. Survival of Didymella bryoniae in infested muskmelon crowns in South Carolina. Plant Dis. 92:1223-1228.
66. Njoroge, S. M. C., Riley, M. B., and Keinath, A. P. 2008. Effect of incorporation of Brassica spp. residues on population densities of soilborne microorganisms and on damping-off and Fusarium wilt of watermelon. Plant Dis. 92: 287-294.
Compendium of Cucurbit Diseases and Pests, Second Edition
Gummy Stem Blight on Watermelon (video)
Watermelon Fungicide Guide
The Post and Courier gardening columns