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​2024 Fellow: Guido Schnabel​

Guido Schnabel was born in Marburg, Germany and received his B.S. and M.S. degrees in agricultural sciences from the Justus Liebig University in Giessen, Germany. He studied approaches to reduce fungal disease on fruits, vegetables, and grape vine through early pathogen diagnosis and fungicides for his Ph.D. dissertation at the University of Bonn and the Kompetenzzentrum–Bodensee before obtaining his degree in plant pathology from the University of Hohenheim in Stuttgart in 1997. He was a postdoctoral research associate in the Department of Botany and Plant Pathology at Michigan State University from 1997 to 2000, where he investigated genetic diversity and fungicide resistance in Venturia species. Schnabel began his position as fruit pathologist with research and Extension responsibilities at Clemson University in 2000, where he is now a professor in the Department of Plant and Environmental Sciences.

Schnabel was honored with the 2011 APS Lee M. Hutchins Award for the molecular characterization and management of fungicide resistance in Monilinia fructicola. He also was honored with the 2015 APS Excellence in Extension Award for the development of resistance screening tools and subsequent Extension programs that allowed effective monitoring of resistance in M. fructicola and Botrytis cinerea. Since then, he has helped scientists worldwide characterize Monilinia species of stone fruits and Botrytis species of small fruits and used his collection of isolates to 1) understand the process by which multifungicide-resistant isolates are selected; 2) identify the genetic basis of fungicide resistance; and 3) refine resistance management strategies for producers. Some of the most noticeable accomplishments include the discovery of point mutations in transcription factor mrr1 in U.S. B. cinerea isolates leading to fludioxonil resistance due to overexpression of the ATP-binding cassette transporter gene AtrB. He has also described key point mutations in multiple fungicide target genes leading to qualitative resistance. He discovered that B. cinerea isolates accumulate resistance to different chemical classes in succession over time and that many field isolates have become simultaneously resistant to up to seven different classes of fungicides. He showed that selection of these multifungicide-resistant isolates not only occurs by direct selection but also by association (“selection by association"), where fungicide resistance traits are often linked to the trait being selected rather than the selectable trait itself. Schnabel helped develop LiDAR-guided spray systems for peach growers in collaboration with USDA scientists that reduce pesticide use, and he is actively researching in lab and field studies alternatives (e.g., polyoxin-D, essential oils, calcium salts, and other biorationals) to traditional fungicides. He developed a new horticultural method involving root collar excavation for peach producers that delays mortality of peach trees on Armillaria root rot-infested replant sites by about 2 years. This system is now being used for new plantings by most large-acreage farms in South Carolina to extend the productive life of peach orchards.

A major strength in Schnabel's program is the integration of research and Extension. His 2015 APS Excellence in Extension Award was based on his excellence in generating highly relevant knowledge, communicating that knowledge to farmers, and documenting its impact. Schnabel's most impactful Extension accomplishments have occurred after the 2015 award, in which he has truly pushed Extension to new levels. Together with a computer science student, he created the MyIPM smartphone app, which is now being used by thousands of agricultural professionals. The value of the app for producers has been recognized by other Extension professionals, and consequently, its content has been voluntarily updated by Extension specialists from NCSU, VT, UGA, PSU, UMass, UMD, MissSU, USDA-ARS, CU, and UF through workshops Schnabel organizes on an annual basis. The app is used by Extension agents and specialists, teachers, and thousands of fruit growers in the United States and elsewhere. Recent spinoffs include MyIPM Row Crop, MyIPM Hawaii, and MyIPM Vegetables. Together with his former graduate student, Madeline Dowling, he produced high-quality disease cycle animations in English and Spanish and movies on MyIPM and brown rot blossom blight and fruit rot management that growers and agents are using for educational purposes.

Schnabel is also an active leader in his home department at Clemson. He has chaired multiple faculty searches and has been the graduate program coordinator for the Department of Plant and Environmental Sciences at Clemson University since 2019. He also has served APS in several ways, including as Plant Disease associate editor (2007–2010) and senior editor (2010–2013). He is also the past chair of the APS Chemical Control Committee (2017) and the APS Fungicide Resistance Management Committee (2015).

Schnabel's reach goes far beyond South Carolina and the United States. Between 2009 and 2014 he traveled three times to Indonesia, the Philippines, and Cambodia as part of a USAID IPM-CRSP and USAID IPM-Innovation Lab-funded project for Southeast Asia. He presented at workshops and field days and consulted scientists, field specialists, and crop consultants on matters of controlling diseases of vegetables and fruits. His commitment to sustainability of disease and fungicide resistance management strategies is apparent based on his long list of accomplishments, including about 200 peer-reviewed papers and book chapters and more than 40 technical publications. His accomplishments in Extension have changed growers' behavior and ensured sustainable production of high-quality fruit. Schnabel has been a mentor to many students, postdocs, and visiting scientists during his career, nearly all of whom have moved on to fulfilling careers in plant pathology. Schnabel's lasting impact on fruit crop pathology, influential mentoring, and innate talents in Extension qualify him for the honor of APS Fellow.