National Program Leader For:

• National Plant Diseases Recovery System
  
  Accession Number: 409350
  
  
• Development of Novel Control Strategies for Diseases Caused by Cellular and Sub-cellular Pathogens
  
  Accession Number: 430593
  
  
• Emerging and Invasive Nematode and Virus Pathogens Affecting Potato
  
  Accession Number: 430676
  
  
• Management of Pathogens for Strawberry and Vegetable Production Systems
  
  Accession Number: 431470
  
  
• Mitigating High Consequence Domestic, Exotic, and Emerging Diseases of Fruits, Vegetables, and Ornamentals
  
  Accession Number: 431483
  
  
• Molecular Identification, Characterization, and Biology of Foreign and Emerging Viral and Bacterial Plant Pathogens
  
  Accession Number: 431767
  
  
• Integrated Management of Soybean Pathogens and Pests
  
  Accession Number: 432114
  
  
• Biology, Ecology, and Genomics of Pathogenic and Beneficial Microorganisms of Wheat, Barley, and Biofuel Brassicas
  
  Accession Number: 432145
  
  
• Epidemiology, Vector-Host Plant Interactions, and Biology of Vegetable and Cucurbit Viruses
  
  Accession Number: 432477
  
  
• Introgression of Novel Resistant Genes and Development of Integrated Production Systems for Managing Reniform Nematodes in Cotton
  
  Accession Number: 432508
  
  
• Biocontrol of Aflatoxin and Other Mycotoxins in Maize Using Non-toxigenic Strains of Aspergillus flavus
  
  Accession Number: 432515
  
  
• Characterization of Molecular Networks in Diseases Caused by Emerging and Persistent Bacterial Plant Pathogens
  
  Accession Number: 432528
  
  
• Utilization of the Rhizosphere Microbiome and Host Genetics to Manage Soil-borne Diseases
  
  Accession Number: 432541
  
  
• Enhancing Plant Protection through Fungal Systematics
  
  Accession Number: 432548
  
  
• Molecular and Genetic Approaches to Manage Cotton Diseases
  
  Accession Number: 432550
  
  
• Characterization and Management of Citrus Pathogens Transmitted by Phloem-Feeding Insect Vectors
  
  Accession Number: 432576
  
  
• Development of New Production Methodologies for Biocontrol Agents and Fastidious Microbes to Improve Plant Disease Management
  
  Accession Number: 432596
  
  
• Genetics and Integrated Management of Plant Parasitic Nematodes in Cotton and Peanut
  
  Accession Number: 432598
  
  
• Biologically Based Technologies for Control of Soil-Borne Pathogens of Vegetables and Ornamentals
  
  Accession Number: 432634
  
  
• Exotic Pathogens of Citrus: Curation, Diagnostics, and Interactions
  
  Accession Number: 432646
  
  
• Biology, Epidemiology, and Detection of Emerging Plant Pathogenic Oomycetes
  
  Accession Number: 432647
  
  
• Characterizing and Detecting Pathogens to Ensure Safe Exchange of Plant Germplasm
  
  Accession Number: 432649
  
  
• Development of Knowledge-based Approaches for Disease Management in Small Fruit and Nursery Crops
  
  Accession Number: 432677
  
  
• Identification, Biology, Epidemiology, and Control of Foreign and Emerging Fungal Plant Pathogens
  
  Accession Number: 432679
  
  
• Microscopy Applications for the Identification and Management of Agricultural Pests and Pathogens
  
  Accession Number: 432685
  
  
• Integrated Management of Fungal Pathogens in Peanut to Reduce Mycotoxin Contamination and Yield Losses
  
  Accession Number: 432690
  
  
• Developing Pathogen- and Plant-Based Genetic Tools for Breeding Disease Resistance in Theobroma cacao
  
  Accession Number: 432718
  
  
• Development of Novel Tools to Manage Fungal Plant Pathogens that Cause Postharvest Decay of Pome Fruit to Reduce Food Waste
  
  Accession Number: 432720
  
  
• Improvement of Genetic Resistance to Multiple Biotic and Abiotic Stresses in Peanut
  
  Accession Number: 434274
  
  
• Biological Control in Integrated Weed Management of Invasive Weeds from Europe, Asia, and Africa
  
  Accession Number: 437656
  
  
• National Predictive Modeling Tool Initiative
  
  Accession Number: 438041
  
  
• Discovery and Development of Biological Control Agents for Weeds that are Invasive in the U.S. and Native to Australia and Asia
  
  Accession Number: 439628
  
  
• Integrated Management of South American Pests and Weeds
  
  Accession Number: 439642
  
  

Publications (Clicking on the reprint icon will take you to the publication reprint.)

Compatibility of Trichoderma asperellum isolates to selected soil fungicides - (Peer Reviewed Journal)

Widmer, T.L. 2019. Compatibility of Trichoderma asperellum isolates to selected soil fungicides. Crop Protection. 120:91-96. https://doi.org/10.1016/j.cropro.2019.02.017.

Phytophthora stricta isolated from Rhododendron maximum in Pennsylvania - (Peer Reviewed Journal)

Widmer, T.L., Mcmahon, M.B., Frederick, R.D. 2018. Phytophthora stricta isolated from Rhododendron maximum in Pennsylvania. Plant Disease. 102:827.

Effects of temperature on germination of sporangia, infection and protein secretion by Phytophthora kernoviae - (Peer Reviewed Journal)

Shelley, B.A., Luster, D.G., Garrett, W.M., Mcmahon, M.B., Widmer, T.L. 2018. Temperature effects Phytophthora kernoviae infection, germination of sporangia and protein secretion. Plant Pathology. 67:719-728.

Recovery of Phytophthora ramorum in plant tissue with mixed infections - (Peer Reviewed Journal)

Widmer, T.L., Tooley, P.W., Camp, M.J. 2018. Recovery of Phytophthora ramorum in plant tissue with mixed infections. European Journal of Plant Pathology. 150:253-258.

The effect of salinity on the growth, sporulation and infection of Phytophthora ramorum - (Peer Reviewed Journal)

Preuett, J.A., Collins, D.J., Luster, D.G., Widmer, T.L. 2016. The effect of salinity on the growth, sporulation and infection of Phytophthora ramorum. Fungal Ecology. 23:123-130.

Bioassay conditions for infection of Pinus radiata seedlings with Phytophthora pinifolia zoospores - (Peer Reviewed Journal)

Widmer, T.L., Dodge, S.C. 2015. Bioassay conditions for infection of Pinus radiata seedlings with Phytophthora pinifolia zoospores. Plant Disease. 99:1204-1209.

Differences in virulence and sporulation of Phytophthora kernoviae isolates originating from two distinct geographical regions - (Peer Reviewed Journal)

Widmer, T.L. 2015. Differences in virulence and sporulation of Phytophthora kernoviae isolates originating from two distinct geographical regions. Plant Disease. 99:460-466.

Phytophthora megakarya - (Peer Reviewed Journal)

Widmer, T.L., Hebbar, P.K. 2013. Phytophthora megakarya. Forest Phytophthoras. doi: 10.5399/OSU/fp.3.1.3386.

Screening selected Gulf Coast forest species for susceptibility to Phytophthora ramorum - (Peer Reviewed Journal)

Preuett, J.A., Collins, D.J., Luster, D.G., Widmer, T.L. 2013. Screening selected Gulf Coast forest species for susceptibility to Phytophthora ramorum. Plant Health Progress. PHP 2013-0730-01-RS.

Can Epiphytes reduce disease symptoms caused by Phytophthora ramorum - (Peer Reviewed Journal)

Widmer, T.L., Dodge, S.C. 2013. Can Epiphytes reduce disease symptoms caused by Phytophthora ramorum. Biological Control. 65:135-141.

Root susceptibility and inoculum production from roots of Eastern United States oak species to Phytophthora ramorum - (Peer Reviewed Journal)

Widmer, T.L., Shishkoff, N., Dodge, S.C. 2012. Root susceptibility and inoculum production from roots of Eastern United States oak species to Phytophthora ramorum. Plant Disease. 96:1675-1682.

Survival of Phytophthora kernoviae oospores, sporangia, and mycelium - (Peer Reviewed Journal)

Widmer, T.L. 2011. Survival of Phytophthora kernoviae oospores, sporangia, and mycelium. New Zealand Journal of Forestry Science. 41S:S15-S23.

Field damage to yellow starthistle infected by Synchytrium solstitiale, and greenhouse maintenance and host range of the fungus - (Peer Reviewed Journal)

Eskandari, F., Bruckart, W.L., Widmer, T.L. 2011. Field damage to yellow starthistle infected by Synchytrium solstitiale, and greenhouse maintenance and host range of the fungus. Plant Disease. DOI: 10.1094/PDis-2-11-0139.

Synchytrium solstitiale: reclassification based on the function and role of resting spores - (Peer Reviewed Journal)

Bruckart, W.L., Eskandari, F., Widmer, T.L. 2011. Synchytrium solstitiale: reclassification based on the function and role of resting spores. Mycologia. DOI: 10.3852/10-286.

Whole plant inoculations of Viburnum species and cultivars testing for susceptibility to Phytophthora ramorum - (Peer Reviewed Journal)

Widmer, T.L. 2010. Whole plant inoculations of Viburnum species and cultivars testing for susceptibility to Phytophthora ramorum. Journal of Environmental Horticulture. 28:197-202.

Phytophthora kernoviae oospore maturity, germination, and infection - (Peer Reviewed Journal)

Widmer, T.L. 2010. Phytophthora kernoviae oospore maturity, germination, and infection. Fungal Biology. doi:10.1016/j.funbio.2010.06.001. 114:661-668.

Root susceptibility and inoculum production from roots of eastern oak species to Phytophthora ramorum - (Abstract Only)

Widmer, T.L., Shishkoff, N., Dodge, S.C. 2010. Root susceptibility and inoculum production from roots of eastern oak species to Phytophthora ramorum. Phytopathology. 100/S136.

Differentiating Phytophthora ramorum and P. kernoviae from other species isolated from foliage of rhododendrons - (Peer Reviewed Journal)

Widmer, T.L. 2010. Differentiating Phytophthora spp. isolated from leaves and stems of rhododendron plants. Plant Health Progress. doi: 10.1094/PHP-2010-0317-01-RS.

Long-term survival of Phytophthora kernoviae oospores - (Proceedings)

Screening Trichoderma asperellum as a Mycoparasite on Phytophthora ramorum - (Proceedings)

Susceptibility of sprouted oak acorns to Phytophthora ramorum zoospores - (Abstract Only)

Widmer, T.L., Dodge, S.C. 2009. Susceptibility of sprouted oak acorns to Phytophthora ramorum zoospores. Phytopathology. 99:5205.

Standardizing the Nomenclature for Clonal Lineages of the Sudden Oak Death Pathogen, Phytophthora ramorum - (Peer Reviewed Journal)

Grunwald, N.J., Goss, E.M., Ivors, K., Garbelotto, M., Martin, F.N., Prospero, S., Hansen, E., Bonants, P., Hamelin, R., Chastagner, G., Werres, S., Rizzo, D.M., Abad, G., Beales, P., Bilodeau, G.J., Blomquist, C., Brasier, C., Briere, S., Chandelier, A., Davidson, J.M., Denman, S., Elliott, M., Fichtner, E.J., Frankel, S.J., Goheen, E.M., De Gruyter, H., Heungens, K., James, D., Kanaskie, A., Mcwilliams, M., Moralejo, E., Osterbauer, N.K., Palm, M.E., Parke, J.L., Shamoun, S.F., Shishkoff, N., Tooley, P.W., Vettraino, A., Webber, J., Widmer, T.L. 2009. Standardizing the nomenclature for clonal lineages of the sudden oak death pathogen, Phytophthora ramorum. Phytopathology. 99:792-795.

Recovery Plan for Phytophthora kernoviae Causing Bleeding Trunk Cankers, Leaf Blight and Stem Dieback in Trees and Shrubs ()

Benson, M., Ivors, K., Koch, F., Fichtner, E., Garbelotto, M., Rizzo, D., Tjosvold, S., Hansen, E., Parke, J., Hong, C., Chastagner, G., Jeffers, S., Woodward-Williams, J., Kim, S., Britton, K., Denitto, G., Frankel, S., Micales, J., Grunwald, N.J., Martin, F.N., Shishkoff, N., Smith, K.L., Tooley, P.W., Widmer, T.L., Bulluck, R., Burnett, G., Ferguson, L., Fowler, G., Garrett, L., Jones, J., Magarey, R., Randall-Schadel, B., Cardwell, K., Draper, M., Chand-Goyal, T. 2009. Recovery Plan for Phytophthora kernoviae Causing Bleeding Trunk Cankers, Leaf Blight and Stem Dieback in Trees and Shrubs. Government Publication/Report. Available at: http://www.ars.usda.gov/SP2UserFiles/Place/00000000/opmp/P.%20kernoviae%2081100.pdf

Comparing necrosis of Rhododendron leaf tissue inoculated with Phytophthora ramorum sporangia or zoospores - (Peer Reviewed Journal)

Widmer, T.L. 2008. Comparing necrosis of Rhododendron leaf tissue inoculated with Phytophthora ramorum sporangia or zoospores. Plant Disease. 93:30-35.

Protocol for maintenance of Synchytrium solstitiale, cause of false rust on yellow starthistle, under greenhouse conditions - (Abstract Only)

Eskandari, F., Bruckart, W.L., Widmer, T.L. 2008. Protocol for maintenance of Synchytrium solstitiale, cause of false rust on yellow starthistle, under greenhouse conditions. Phytopathology. 98(6,Supplement)S214-215

Comparing New Zealand and United Kingdom isolates of Phytophthora kernoviae - (Abstract Only)

Widmer, T.L. 2008. Comparing New Zealand and United Kingdom isolates of Phytophthora kernoviae. Phytopathology. 98:S171

Isolation and identification of mycoparasitic isolates of Trichoderma asperellum with potential for suppression of black pod disease of cacao in Cameroon - (Peer Reviewed Journal)

Tondje, P., Roberts, D.P., Bon, M., Widmer, T.L., Samuels, G.J., Ismaiel, A.A., Begoude, A., Tchana, T., Nyemb-Tshomb, E., Ndoumbe-Nkeng, M., Bateman, D., Fontem, D., Hebbar, K. 2007. Isolation and identification of mycoparasitic isolates of Trichoderma asperellum with potential for suppression of black pod disease of cacao in Cameroon. Biocontrol.

Investigating the potential of biological control against Phytophthora ramorum - (Proceedings)

Widmer, T.L. 2008. Investigating the potential of biological control against Phytophthora ramorum. Sudden Oak Death Science Symposium. Frankel, S.J., Kliejunns, J.T. and Palmieri, K. M. (eds). USDA Forest Service Gen. Tech. Rep. PSW-GTR-214, Albany, CA. p. 491

AN IPM PROGRAM FOR THE MANAGEMENT OF FUNGAL LEAF BLIGHT DISEASES OF CARROT IN NEW YORK - (Peer Reviewed Journal)

Gugino, B.K., Carroll, J.E., Widmer, T.L., Chen, P., Abawi, G.S. 2007. An ipm program for the management of fungal leaf blight diseases of carrot in new york. Plant Disease 91:59-65

FIELD EVALUATION OF CARROT CULTIVARS FOR SUSCEPTIBILITY TO FUNGAL LEAF BLIGHT DISEASES IN NEW YORK - (Peer Reviewed Journal)

Gugino, B.K., Carroll, J.E., Widmer, T.L., Chen, P., Abawi, G.S. 2007. Field evaluation of carrot cultivars for susceptibility to fungal leaf blight diseases in new york. Crop Protection 26:709-714

IMPACT OF SYNCHYTRIUM SOLSTITIALE ON YELLOW STARTHISTLE SEEDLINGS AND MATURE PLANTS - (Abstract Only)

Widmer, T.L. 2006. Impact of synchytrium solstitiale on yellow starthistle seedlings and mature plants. Phytopathology 96:S122.

Prospects for Biological Control of Teasels, Dipsacus SPP, in the United States - (Peer Reviewed Journal)

Rector, B.G., Harizanova, V., Sforza, R., Widmer, T.L., Wiedenmann, R.N. 2006. PROSPECTS FOR BIOLOGICAL CONTROL OF TEASELS, DIPSACUS SPP., IN THE UNITED STATES. Biological Control. 1:1-14.

FACTORS AFFECTING INFECTION OF YELLOW STARTHISTLE (CENTAUREA SOLSTITIALIS) BY SYNCHYTRIUM SOLSTITIALE, CAUSAL AGENT OF FALSE RUST DISEASE - (Peer Reviewed Journal)

Widmer, T.L., Guermache, F. 2006. Factors affecting infection of yellow starthistle (centaurea solstitialis) by synchytrium solstitiale, causal agent of false rust disease. Plant Disease. 90:425-428

CRYOPRESERVATION OF SYNCHYTRIUM SOLSTITIALE IN PLANTA - (Peer Reviewed Journal)

Widmer, T.L. 2006. Cryopreservation of synchytrium solstitiale in planta. Plant Disease. 90:429-432

BIOLOGICAL CONTROL OF YELLOW STARTHISTLE: NEW PROSPECTS FOR AN OLD PROBLEM. - (Abstract Only)

Smith, L., Cristofaro, M., Pitcairn, M., Bruckart, W.L., Woods, D., Widmer, T.L., Berner, D.K., Drew, A.E. 2004. Biological control of yellow starthistle: new prospects for an old problem.. Ecological Society of America Proceedings.

CENTAUREA SOLSTITIALIS : ROOT EXTRACT INHIBITION OF PLANT PATHOGENIC FUNGI - (Proceedings)

Guermache, F., Widmer, T.L. 2004. Centaurea solstitialis : root extract inhibition of plant pathogenic fungi. 12th International Conference on Weed Biology, Dijon, France pp. 427-431. INRA, Dijon, France.

FORMULATION OF PHOMA EXIGUA, POTENTIAL BIOCONTROL AGENT AGAINST CENTAUREA SOLSTITIALIS - (Proceedings)

Laurent, N., Gras, S., Quimby Jr, P.C., Widmer, T.L. 2004. Formulation of phoma exigua, potential biocontrol agent against centaurea solstitialis. 12th International Conference on Weed Biology, Dijon, France pp.399-406. INRA, Dijon, France.

FORMULATION OF SCLEROTINIA SCLEROTIORUM FOR USE AGAINST CIRSIUM ARVENSE - (Peer Reviewed Journal)

Quimby Jr, P.C., Gras, S., Widmer, T.L., Meikle, W.G., Sands, D. 2004. Formulation of sclerotinia sclerotiorum for use against cirsium arvense. Journal of Plant Diseases and Protection. Special Issue XIX:491-495

FILTRATES OF RHIZOSPHERE BACTERIA SUPPRESSIVE TO CENTAUREA SOLSTITIALIS SEED GERMINATION - (Peer Reviewed Journal)

Widmer, T.L., Guermache, F. 2004. Filtrates of rhizosphere bacteria suppressive to Centaurea solstitialis seed germination. Journal of Plant Diseases and Protection. Special Issue XIX:497-502

EXPLORATION FOR PLANT PATHOGENS AGAINST TAENIATHERUM CAPUT-MEDUSAE (MEDUSAHEAD) - (Proceedings)

Widmer, T.L., Sforza, R. 2004. Exploration for plant pathogens against taeniatherum caput-medusae (medusahead). XI Symposium on Biological Control of Weeds (eds Cullen, J.M., Briese, D.T., Kriticos, D.J., Londsdale, W.M., Morin, L. and Scott, J.K.) pp. 193-197. CSIRO Entomology, Canberra, Australia.

MOLECULAR IDENTIFICATION OF A NEW MEMBER OF THE CLOVER PROLIFERATION PHYTOPLASMA GROUP (16SRVI) ASSOCIATED WITH CENTAUREAE SOLSTITIALIS VIRESCENCE IN ITALY. - (Peer Reviewed Journal)

Faggioli, F., Pasquini, G., Campobasso, G., Widmer, T.L., Quimby Jr, P.C. 2004. Molecular identification of a new member of the clover proliferation phytoplasma group (16srvi) associated with centaureae solstitialis virescence in italy.. European Journal Of Plant Pathology. 110:353-360

In Vitro Culturing of Yellow Starthistle (Centaurea solstitialis) for Screening Biological Control Agents. - (Peer Reviewed Journal)

Guermache, F., Vidal, K., Widmer, T.L. 2004. In Vitro Culturing of Yellow Starthistle (Centaurea solstitialis) for Screening Biological Control Agents. Biological Control 30:330-335.

PLANT PATHOLOGY AND BIOLOGICAL CONTROL OF INVASIVE WEEDS ()

BRUCKART, W.L., BERNER, D.K., CAESAR, A.J., WIDMER, T.L. PLANT PATHOLOGY AND BIOLOGICAL CONTROL OF INVASIVE WEEDS. Biological Control of Invasive Plants in the United States. In Plant Pathology and Biological Control of Invasive Weeds. E.M. Combs, J.K. Clark, G.L. Piper, and A.F. Cofrancesco (EDS). Oregon State University Press, Corvallis, OR. 2004.

SYNCHYTRIUM SOLSTITIALE SP. NOV. CAUSING A FALSE RUST ON CENTAUREA SOLSTITIALIS IN FRANCE - (Peer Reviewed Journal)

Widmer, T.L. 2004. Synchytrium solstitiale sp. nov. causing a false rust on centaurea solstitialis in france. Mycologia. 96(2):407-410

THE POTENTIAL CONTRIBUTION OF NATURAL ENEMIES FROM MEDITERRANEAN EUROPE TO THE MANAGEMENT OF THE INVASIVE WEED ARUNDO DONAX (GRAMINAE:ARUNIDINAE) IN THE USA - (Proceedings)

Kirk, A.A., Widmer, T.L., Campobasso, G., Carruthers, R.I., Dudley, T. 2003. The potential contribution of natural enemies from Mediterranean Europe to the management of the invasive weed arundo donax (graminae:arunidinae) in the usa. In: Proceedings of the California Invasive Plant Council Symposium, Vol. 7 (ed. Pirosko, C.) pp. 62-68. California Invasive Plant Council, Berkley, CA, USA.

FIRST REPORT OF FUSARIUM ARTHROSPORIOIDES ON MEDUSAHEAD (TAENIATHERUM CAPUT-MEDUSAE) AND PRELIMINARY TESTS FOR HOST-SPECIFICITY - (Peer Reviewed Journal)

SEIGWART, M., BON, M., WIDMER, T.L., CRESPY, N., SFORZA, R. FIRST REPORT OF FUSARIUM ARTHROSPORIOIDES ON MEDUSAHEAD (TAENIATHERUM CAPUT-MEDUSAE) AND PRELIMINARY TESTS FOR HOST-SPECIFICITY. PLANT PATHOLOGY. 2003.

FIRST REPORT OF PHOMA EXIGUA ON CENTAUREA SOLSTITIALIS [ASTERACEAE] IN RUSSIA - (Peer Reviewed Journal)

Widmer, T.L., Castlebury, L.A., Rossman, A.Y. 2002. First report of phoma exigua on centaurea solstitialis [asteraceae] in russia. Plant Disease 86:922

IMPACT OF ORGANIC MATTER MANAGEMENT ON PLANT-PARASITIC NEMATODES, THEIR DAMAGE TO HOST CROPS AND SOIL HEALTH - (Peer Reviewed Journal)

RELATIONSHIP BETWEEN LEVELS OF CYANIDE IN SUDANGRASS HYBRIDS INCORPORATED INTO SOIL AND SUPPRESSION OF MELOIDOGYNE HAPLA - (Peer Reviewed Journal)

Widmer, T.L., Abawi, G.S. 2002. Relationship between levels of cyanide in sudangrass hybrids incorporated into soil and suppression of Meloidogyne hapla. Journal of Nematology. 34:16-22.

IMPACT OF SOIL HEALTH MANAGEMENT PRACTICES ON SOILBORNE PATHOGENS AND ROOT DISEASES OF VEGETABLES. ()

Widmer, T.L., Abawi, G.S. 2000. Impact of soil health management practices on soilborne pathogens and root diseases of vegetables. Applied Soil Ecology. 15:37-47.

MECHANISM OF SUPPRESSION OF MELOIDOGYNE HAPLA AND ITS DAMAGE BY A GREEN MANURE OF SUDAN GRASS - (Peer Reviewed Journal)

Widmer, T.L., Abawi, G.S. 2000. Mechanism of suppression of meloidogyne hapla and its damage by a green manure of sudan grass. Plant Disease. 84:562-568.