The Lee M. Hutchins Award is presented to the author or authors of published research on basic or applied aspects of diseases of perennial fruit plants (tree fruits, tree nuts, small fruits, and grapes, including tropical fruits, but excluding vegetables).
Dr. Walter (Walt) F. Mahaffee was born in South Carolina and received his Ph.D. in 1996 in plant pathology from Auburn University. He immediately joined the U.S. Department of Agriculture, Agricultural Research Service as a Research Plant Pathologist in the Horticultural Crops Research Unit with primary responsibilities for foliar diseases of small fruit and nursery crops. He is also a Courtesy Professor in the Department of Botany and Plant Pathology at Oregon State University.
Mahaffee has addressed some of the most difficult questions in Plant Disease epidemiology and ecology and has applied answers from those questions to improve management options for grape powdery mildew and other aerially dispersed pathogens. This is best exemplified in his multi-decade pursuit to understand and model pathogen dispersion at scales ranging from individual plants to entire landscapes, all of which has been published in APS journals. Mahaffee and colleagues were some of the first researchers to effectively couple spore trapping with PCR to detect and quantify airborne inoculum of Erysiphe necator (Phytopathology 97:1290-1297). Sampling air for inoculum of plant pathogens in fruit and other crops by PCR is now commonly employed in biosurveillance, as a part of early warning systems for disease onset, and as decision aid. Much of this expanding literature can be traced back to Mahaffee’s initial work in this space. In fact, many researchers across the U.S. make use of his custom, open-source spore traps where he pioneered 3D-printing and electronic design to produce simple, inexpensive devices (Plant Disease 108:1910-1922; 108:1923-1936). He has provided consultation on PCR-based inoculum detection and spore trapping to at least 26 laboratories and companies.
Mahaffee has pursued rigorous and precise answers to seemingly basic questions such as “Where should a spore trap be placed?”, “How many traps are needed to represent a given field?”, and “How does inoculum quantity translate into management for a given grower?” Mahaffee and his laboratory team members have developed pioneering methods for growers themselves to conduct point-of-care LAMP assays for detection of Erysiphe necator in their vineyards and derived action thresholds to turn PCR results into improved spray decisions (Phytopathology 101:1246-1252).
For the past decade, Mahaffee has been a driving force in interdisciplinary research that is at the forefront of aerobiology, pathogen detection, and biophysical modeling, culminating in a widely cited review article in Phytopathology (106:420-431) and a recent Plant Disease Feature Article (107:13-33). These two articles have each been downloaded more than 4600 times. He has described mechanisms underlying complex patterns of dispersal that were previously out- of-reach to phytopathologists and provides an outstanding and rare example of the merits of bringing physical sciences into plant pathology. His work in this area is nothing less than foundational for anyone interested in air sampling and pathogen dispersion. His dispersion research has also led to the development of crop growth models integrating spore dispersal with crop growth and management in collaborations with engineers.
Mahaffee and colleagues have extended their pathogen detection research to understand and mitigate fungicide resistance in the Erysiphe necator. His research has developed rapid, cost- effective monitoring methods for detecting QoI fungicide resistance in the pathogen from the gloves or vineyards workers (Plant Disease 107:3096-3105). This has enabled growers to make more informed decisions about fungicide selection in individual fields to improve disease control and avoid ineffective fungicides.
One of Mahaffee's most outstanding achievements is his ability to bridge the gap between basic research and practical application. He has productive and collegial working relationships with growers and other members of the winegrape industry, which grounded his work in addressing problems they face. He has been intentional about how he approaches research to ensure it remains relevant. His research has been instrumental in the commercialization of inoculum monitoring as a decision aid in viticulture in Oregon and elsewhere. He is also the go-to source for the western US winegrape industry for credible and trusted advice on fungicide resistance and resistance management. The cumulative impact of Mahaffee’s research is greatly improved understanding of when and where E. necator occurs and how best to manage the disease. Inoculum detection as a decision aid for E. necator is now commercially available in California and Oregon and was shown to reduce fungicide applications by 50% while saving on average $200 per acre, a potential savings of $1.5 to $2.3 million annually in Oregon alone. His successful efforts to transfer the research products to several commercial companies was recognized by the Outstanding Commercialization Success Award conferred by the Federal Laboratory Consortium for Technology Transfer Far-West Region. This award is one of the most prestigious honors in technology transfer that recognizes development and transfer of truly outstanding technologies.
His service to the next generation of plant pathologists is also evident. Mahaffee is active in the Department of Botany and Plant Pathology at Oregon State University. He has mentored over 20 graduate and undergraduate students at multiple institutions, where they continue to impact diseases of fruit and other areas. His advocacy for these students as well as his rigorous scientific standards and ethics are an enduring benefit to the next generation of plant pathologists working with perennial fruit plants.
Mahaffee’s significant and sustained contributions to original research on grape powdery mildew over the past decade, as documented in his series of papers in APS journals and tangible benefits to the winegrape industry, are unmatched. The value of these contributions make Walt Mahaffee a most deserving recipient of the Lee M. Hutchins Award.
