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United States Department of Agriculture

Agricultural Research Service

Walter F. Mahaffee (Walt)

Research Plant Pathologist


Publications (Clicking on the reprint icon Reprint Icon will take you to the publication reprint.)
A scalable plant-resolving radiative transfer model based on optimized GPU ray tracing - (Peer Reviewed Journal) - (24-Aug-14)
Effect of vegetative canopy architecture on vertical transport of massless particles - (Peer Reviewed Journal)
Bailey, B.N., Stoll, R., Pardyjak, E.R., Mahaffee, W.F. 2014. Effect of vegetative canopy architecture on vertical transport of massless particles. Atmospheric Environment. 95:480-489.
The use and role of predictive systems in disease management - (Peer Reviewed Journal)
Gent, D.H., Mahaffee, W.F., Mcroberts, N., Pfender, W.F. 2013. The use and role of predictive systems in disease management. Annual Review of Phytopathology. 51:267-89.
Invaded range of the blackberry pathogen Phragmidium violaceum in the Pacific Northwest of the USA and the search for its provenance - (Peer Reviewed Journal)
Morin, L., Gomez, D., Evans, K., Neill, T.M., Mahaffee, W.F., Linde, C. 2013. Invaded range of the blackberry pathogen Phragmidium violaceum in the Pacific Northwest of the USA and the search for its provenance. Biological Invasions. 15(8):1847-1861.
Powdery mildew - (Book / Chapter)
Mahaffee, W.F., Glawe, D. 2014. Powdery mildew. Compendium of Rhododendron and Azalea Diseases and Pests. Pp 41-44.
Association of spring pruning practices with severity of powdery 1 mildew and downy mildew on hop - (Peer Reviewed Journal) - (09-Apr-12)
Sensitivity of disease management decision aids to temperature input errors associated with out-of-canopy and reduced time-resolution measurements - (Peer Reviewed Journal)
Pfender, W.F., Gent, D.H., Mahaffee, W.F. 2012. Sensitivity of disease management decision aids to temperature input errors associated with out-of-canopy and reduced time-resolution measurements. Plant Disease. 96:726-736.
Inoculum detection for managing grape powdery mildew - (Popular Publication)
Mahaffee, W.F., Grove, G., Stoll, R. 2011. Inoculum detection for managing grape powdery mildew. Practical Winery and Vineyards. Spring. p. 26-32.
Subsurface examination of a foliar biofilm using scanning electron- and focused-ion-beam microscopy - (Peer Reviewed Journal)
Wallace, P., Arey, B., Mahaffee, W.F. 2011. Subsurface examination of a foliar biofilm using scanning electron- and focused-ion-beam microscopy. Micron. 42:579-585.
Decision Aids for Multiple-Decision Disease Management as Affected by Weather Input Errors - (Peer Reviewed Journal)
Pfender, W.F., Gent, D.H., Mahaffee, W.F., Coop, L.B., Fox, A. 2011. Decision Aids for Multiple-Decision Disease Management as Affected by Weather Input Errors. Phytopathology. 101:644-653.
The impact of canopy geometry on particle dispersion gradients in sparse agricultural canopies - (Proceedings)
Bailey, B., Stoll, R., Mahaffee, W.F., Pardyjak, E. 2010. The impact of canopy geometry on particle dispersion gradients in sparse agricultural canopies. Agricultural and Forest Meteorology Conference Proceedings. Available: http://ams.confex.com/ams/19Ag19BLT9Urban/techprogram/MEETING.HTM.
Permanent Genetic Resources added to Molecular Ecology Resources Database 1 December 2009–31 January 2010 - (Peer Reviewed Journal)
C., Gomez, D., Morin, L., Evans, K., Mahaffee, W.F., Neill, T.M., Grunwald, N.J.,Molecular Ecology Resources Primer Development Consortium. 2010. Permanent genetic resources added to molecular ecology resources database 1 December 2009–31 January 2010. Molecular Ecology Resources. 10:576-579.
Development of 11 polymorphic microsatellite markers for the blackberry rust fungus Phragmidium violaceum - (Peer Reviewed Journal)
Gomez, D., Morin, L., Evans, K., Mahaffee, W.F., Neill, T.M., Grunwald, N.J. 2010. Development of 11 polymorphic microsatellite markers for the blackberry rust fungus Phragmidium violaceum. Molecular Ecology Resources. 10:576-579.
Factors Influencing Epidemiology and Management of Blackberry Rust in Cultivated Rubus laciniatus - (Peer Reviewed Journal)
Johnson, K., Mahaffee, W.F. 2010. Factors influencing epidemiology and management of blackberry rust in cultivated Rubus laciniatus. Plant Disease. 94:581-588.
Development and Use of Fluorescent Antibody and qPCR Protocols for the Electrostatic Spore Trap - (Abstract Only)
Schneider, R.W., Haudenshield, J.S., Hartman, G.L., Mahaffee, W.F. 2010. Development and Use of Fluorescent Antibody and qPCR Protocols for the Electrostatic Spore Trap [abstract]. American Phytopathological Society National Meeting, August 1-5, 2009, Portland, Oregon. 99:S115.
The relationship of biofilm production to biocontrol activity of Burkholderia pyrrocinia FP62 - (Abstract Only)
Wallace, P., Mahaffee, W.F., Press, C.M., Larsen, M.M., Neill, T.M. 2009. The relationship of biofilm production to biocontrol activity of Burkholderia pyrrocinia FP62. American Phytopathological Society Abstracts. p. 569.
Foliar biofilms of Burkholderia pyrrocinia FP62 on geraniums - (Abstract Only)
Wallace, P., Mahaffee, W.F., Neill, T.M. 2009. Foliar biofilms of Burkholderia pyrrocinia FP62 on geraniums. American Phytopathological Society Abstracts. p. 568.
Forecast and virtual weather driven plant disease risk modeling system - (Abstract Only)
Coop, L., Fox, A., Mahaffee, W.F., Gent, D.H., Pfender, W.F., Thomas, C. 2009. Forecast and virtual weather driven plant disease risk modeling system. American Phytopathological Society Abstracts. p. 873.
Effect of Temperature on the Sporulation and Infectivity of Podosphaera macularis on Humulus lupulus - (Peer Reviewed Journal)
Peetz, A., Mahaffee, W.F., Gent, D.H. 2009. Effect of temperature on the sporulation and infectivity of Podosphaera macularis on Humulus lupulus. Plant Disease. 93:281-286.
Spatial and Temporal Stability of the Estimated Parameters of the Binary Power Law - (Peer Reviewed Journal)
Gent, D.H., Turechek, W., Mahaffee, W.F. 2008. Spatial and Temporal Stability of the Estimated Parameters of the Binary Power Law. Phytopathology. 98:1107-1117.
Powdery Mildew Resistant Hop Germplasm Release: 'Kazak 2000' - (Abstract Only)
Hummer, K.E., Gent, D.H., Henning, J.A., Mahaffee, W.F., Ocamb, C. 2008. Powdery Mildew Resistant Hop Germplasm Release: 'Kazak 2000' [abstract]. Acta Horticulturae. p.59
Powdery Mildew - (Book / Chapter)
Mahaffee, W.F., Englhard, B., Gent, D.H. 2009. Powdery mildew. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 25-31.
The Genus Humulus - (Book / Chapter)
Mahaffee, W.F., Pethybridge, S. 2009. The genus Humulus. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 1-5.
Gray Mold - (Book / Chapter)
Mahaffee, W.F., Englhard, B. 2009. Gray mold. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 24-25.
Compendium of Hop Diseases and Pests - (Book / Chapter)
Mahaffee, W.F., Pethybridge, S.J.,Gent, D.H. editors. 2009. Compendium of hop diseases and pests. St. Paul, MN: APS Press. 93 p.
Nutrient Imbalances - (Book / Chapter)
Mahaffee, W.F., Pethybridge, S., Gent, D.H. 2009. Nutrient imbalances. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 75-77.
Cone Early Maturity - (Book / Chapter) - (05-Apr-08)
Cone Early Maturity - (Book / Chapter)
Mahaffee, W.F. 2009. Cone early maturity. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 73-74.
Injuries Caused by Environmental Factors - (Book / Chapter)
Mahaffee, W.F., Pethybridge, S., Gent, D.H. 2009. Injuries caused by environmental factors. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p.77-78.
Chemical Injury - (Book / Chapter)
Gent, D.H., Pethybridge, S., Mahaffee, W.F. 2009. Chemical injury. In: Mahaffee, W.F., Pethybridge, S.J., and Gent, D.H. editors. Compendium of Hop Diseases and Pests. St. Paul, MN: APS Press. p. 78-80.
A Decade of Hop Powdery Mildew in the Pacific Northwest - (Peer Reviewed Journal)
Gent, D. H., Nelson, M. E., George, A. E., Grove, G. G., Mahaffee, W. F., Ocamb, C. M., Barbour, J. D., Peetz, A., and Turechek, W. W. 2008. A decade of hop powdery mildew in the pacific northwest. Online. Plant Health Progress doi:10.1094/PHP-2008-0314-01-RV.
Sequential sampling for estimation and classification of the incidence of hop powdery mildew II: Cone sampling - (Peer Reviewed Journal)
Gent, D.H., Turechek, W., Mahaffee, W.F. 2007. Sequential sampling for estimation and classification of the incidence of hop powdery mildew II: Cone sampling. Plant Disease. 91:1013-1020.
Sequential sampling for estimation and classification of the incidence of hop powdery mildew I: Leaf sampling - (Peer Reviewed Journal)
Gent, D.H., Turechek, W., Mahaffee, W.F. 2007. Sequential sampling for estimation and classification of the incidence of hop powdery mildew I: Leaf sampling. Plant Disease. 91:1002-1012.
Spatial Heterogeneity of the Incidence of Powdery Mildew on Hop Cones - (Peer Reviewed Journal)
Gent, D.H., Mahaffee, W.F., Turechek, W. 2006. Spatial Heterogeneity of the Incidence of Powdery Mildew on Hop Cones. Plant Disease.
Detection of Erysiphe (Uncinula) Necator Using the Polymerase Chain Reaction and Species-Specific Primers - (Peer Reviewed Journal)
Falacy, J. S., Grove, G. G., Mahaffee, W. F., Galloway, H., Glawe, D. A., Larsen, R. C., and Vandermark, G. J. 2007. Detection of Erysiphe necator in air samples using the polymerase chain reaction and species-specific primers. Phytopathology 97:1290-1297.
Variability Associated with Suppression of Gray Mold (Botrytis cinerea) on Geranium (Pelargonium x hortorum) by Foliar Applications of Non-Aerated and Aerated Compost Teas - (Peer Reviewed Journal)
Scheuerell, S., Mahaffee, W.F. 2006. Variability associated with suppression of gray mold (Botrytis cinerea) on geranium (Pelargonium x hortorum) by foliar applications of non-aerated and aerated compost teas. Plant Disease. 90:1201-1208.
Compost Teas: Alternatives to Traditional Biological Control Agents - (Book / Chapter)
Mahaffee, W.F. and Scheuerell, S. 2006. Compost teas: Alternatives to traditional biological control agents. In: Baily, M.J., Lilley, A.K., Timms-Wilson, T.M., and Spencer-Phillips, P.T.N. editors. Microbial Ecology of Aerial Plant Surfaces. Oxford, England: CABI. p.165-179.
Atypical Disease Response to Hop Powdery Mildew - (Abstract Only)
Smith, J.M., Hummer, K.E., Mahaffee, W.F. 2005. Atypical disease response to hop powdery mildew [abstract]. Hortscience. 40(4):1034.
The Rise and Fall of Hop Powdery Mildew in the Pacific Northwest - (Abstract Only)
Mahaffee, W.F., Turechek, W., Thomas, C.S., Grove, G.G., Galloway, H., Nelson, M., Ocamb, C.M. The rise and fall of hop powdery mildew in the pacific northwest. Phytopathology.
Quantification of Airborne Hop Powdery Mildew Inoculum, a Molecular Approach. - (Abstract Only)
Peetz, A.B., Mahaffee, W.F., Grove, G.G. 2005. Quantification of airborne hop powdery mildew inoculum, a molecular approach.. Phytopathology.
Detection of Podosphaera Clandestine in the Air of Cherry Orchards Using Pcr and Species-Specific Primers - (Abstract Only)
Grove, G.G., Galloway, H., Lunden, J., Spotts, R.A., Mahaffee, W.F. 2005. Detection of podosphaera clandestine in the air of cherry orchards using pcr and species-specific primers. Phytopathology.
Rapid Detection and Quantification of Airborne Hop Powdery Mildew Inoculum - (Abstract Only)
Peetz, A.B., Mahaffee, W.F., Jackson, J., Grove, G.G., Galloway, H. 2005. Rapid detection and quantification of airborne hop powdery mildew inoculum. Phytopathology. 95:S81.
Detection of Erysiphe Necator in the Air of Grape Vineyards in Eastern Washington - (Abstract Only)
Grove, G.G., Falacy, J., Galloway, H., Mahaffee, W.F., Turechek, W., Peetz, A.B. 2005. Detection of erysiphe necator in the air of grape vineyards in eastern washington. Phytopathology. 95:S36.
Suppression of Seedling Damping-off Caused by Pythium Ultimum, Pythium Irregulare, and Rhizoctonia Solani in Container Media Amended with a Diverse Range of Pacific Northwest Compost Sources - (Peer Reviewed Journal)
Scheuerell, S.J., Sullivan, D.M., Mahaffee, W.F., 2005. Suppression of seedling damping-off caused by pythium ultimum, pythium irregulare, and rhizoctonia solani in container media amended with a diverse range of pacific northwest compost sources. Phytopathology.95(3):306-315.
High Temperature-Dependent Resistance to Powdery Mildew in Hops - (Abstract Only)
Jackson, J., Hummer, K.E., Mahaffee, W.F. 2004. High temperature-dependent resistance to powdery mildew in hops [abstract]. Acta Horticulturae. p. 26.
Compost Tea As a Container Media Drench for Supressing Seedling Damping-off Caused by Pythium Ultimum - (Peer Reviewed Journal)
Scheurell, S., Mahaffee, W.F. 2004. Compost tea as a container media drench for supressing seedling damping-off caused by pythium ultimum. Phytopathology. 94(11)1156-1163.
Spatial Pattern Analysis of Hop Powdery Mildew in the Pacific Northwest: Implication for Sampling - (Peer Reviewed Journal)
Turechek, W., Mahaffee, W.F. 2004. Spatial pattern analysis of hop powdery mildew in the pacific northwest: implication for sampling. Phytopathology. 94(10):1116-1128.
Microbial Recolonization of Compost after Peak Heating Needed for the Rapid Development of Damping-off Suppression Caused by Pythium Ultimum - (Peer Reviewed Journal)
Scheuerell, S., Mahaffee, W.F. 2005. Microbial recolonization of compost after peak heating needed for the rapid development of damping-off suppression caused by pythium ultimum. Compost Science and Utilization. 13:65-71.
Registration of Newport Hop - (Peer Reviewed Journal)
Henning, J.A., Townsend, M.S., Mahaffee, W.F., Kenny, S., Haunold, A. 2004. Registration of newport hop. Crop Science.44:1018-1019.
Plant Growth Regulator Effects of Fungicides Applied to Hop for Control of Powdery Mildew - (Proceedings)
Nelson, M.E., Eastwell, K.C., Ocamb, C.M., Mahaffee, W.F., Kenny, S.T., Grove,G. G. Plant Growth Regulator Effects Of Fungicides Applied To Hop For Control Of Powdery Mildew.
Responding to An Introduced Pathogen: Podsphaera Macularis (Hop Powdery Mildew) in the Pacific Northwest - (Peer Reviewed Journal)
Mahaffe, W.F., Thomas, C.S., Turechek, W.W., Ocamb, C.M., Nelson, M.E., Fox, A., Gubler, W.D. Responding to an Introduced Pathogen: Podosphaera macularis (Hop Powdery Mildew) in the Pacific Northwest. Online. Plant Health Progress doi:10.1094/PHP-2003-1113-07-RV.
Effect of Variable Temperature on the Infection Frequency of Sphaerotheca Macularis on Humulus Lupulus. - (Peer Reviewed Journal)
Mahaffee, W.F., Turechek, W., Ocamb, C. Effect of variable temperature on the infection frequency of Podosphaera macularis on Humulus lupulus. Phytopathology. 2003. v93 p. 1587-1592.
Effect of Variable Temperature on the Infection Frequency of Sphaerotheca Macularis on Humulus Lupulus. - (Peer Reviewed Journal)
Mahaffee, W.F., Turechek, W., Ocamb, C. Effect of variable temperature on the infection frequency of Podosphaera macularis on Humulus lupulus. Phytopathology. 2003. v93 p. 1587-1592.
Effect of Variable Temperature on the Infection Frequency of Sphaerotheca Macularis on Humulus Lupulus. - (Peer Reviewed Journal)
Mahaffee, W.F., Turechek, W., Ocamb, C. Effect of variable temperature on the infection frequency of Podosphaera macularis on Humulus lupulus. Phytopathology. 2003. v93 p. 1587-1592.
Effect of Variable Temperature on the Infection Frequency of Sphaerotheca Macularis on Humulus Lupulus. - (Peer Reviewed Journal)
Mahaffee, W.F., Turechek, W., Ocamb, C. Effect of variable temperature on the infection frequency of Podosphaera macularis on Humulus lupulus. Phytopathology. 2003. v93 p. 1587-1592.
Role of Biofilms in Biocontrol of Botrytis Cinerea - (Abstract Only)
Press, C.M., Mahaffee, W.F., Roche, M.M., Sechler, T.M., Davis, A.L. Role Of Biofilms In Biocontrol Of Botrytis Cinerea.
Microscopic Evaluation of Phyllosphere Colonization by a Biofilm-Forming Biocontrol Agent - (Abstract Only)
Sechler, T.M., Mahaffee, W.F., Press, C.M., Roche, M.M., Dileone, J., Soeldner, A.H. Microscopic Evaluation Of Phyllosphere Colonization By A Biofilm-Forming Biocontrol Agent.
Characterization of the Biofilm Phenotype of Burkholderia SP., Fp62 and Its Role in Biocontrol - (Abstract Only)
Roche, M.M., Mahaffee, W.F., Press, C.M., Sechler, T.M., Davis, A.L. Characterization Of The Biofilm Phenotype OF Burkholderia SP., FP62 And Its Role In Biocontrol.
The Impact of Vine Shelter Use on the Development of Grape Powdery Mildew - (Peer Reviewed Journal) - (02-May-01)
Control of Botrytis During Plant Propagation - (Proceedings) - (01-May-00)
Comparative Evaluation of Endophytic Bacteria from Chinese and U.S. Cotton Cultivars - (Proceedings) - (01-Nov-97)
Recent Studies on the Microbial Ecology of Bacterial Endophytes in Plants - (Proceedings) - (01-Sep-97)
Bacterial Endophytes in Agricultural Crops - (Review Article) - (15-Jul-97)
Biocontrol Procucts for Plant Disease Control - (Book / Chapter) - (01-Apr-97)
Biological Control Agents for Plant Diseases Registered in Oregon - (Other) - (01-Apr-97)
Comparative Analysis of Antibiotic Resistance, Immunofluorescent Colony Staining, and a Transgenic Marker (Bioluminescence) for Monitoring the Environmental Fate of a Rhizobacterium - (Peer Reviewed Journal) - (19-Jan-97)
Temporal Changes in the Bacterial Communities of Soil, Rhizosphere, and Endoriza Associated with Field Grown Cucumber (Cucumis Sativus L.) - (Peer Reviewed Journal) - (20-Dec-96)
Bacterial Communities of the Rhizosphere and Endorhiza Associated with Field-Grown Cucumber Plants Inoculated with a Plant Growth-Promoting Rhizobacterium Or Its Genetically Modified Derivative - (Peer Reviewed Journal) - (18-Nov-96)
Last Modified: 10/26/2011
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