Mark Mazzola grew up in the greater Boston area. He earned his B.S. degree in forestry in 1982 and M.S. degree in forest pathology in 1985 from the University of Vermont and his Ph.D. degree in plant pathology from Washington State University in 1990. He conducted work as a post-doctoral research associate at Kansas State University from 1990 to 1993 and at the USDA-ARS Root Disease & Biological Control Research Unit from 1993 to 1995. He was appointed as an adjunct faculty in the Washington State University Department of Plant Pathology in 1996 and in the Department of Crop & Soil Sciences in 2007 and has served as adjunct professor in the Department of Horticulture at Oregon State University and as extraordinary professor in the Department of Plant Pathology at Stellenbosch University, South Africa.
Mazzola has established himself as a distinguished scientist of both national and international renown in the field of plant pathology. He has made noteworthy contributions to the field through his efforts to develop environmentally sustainable practices for the control of diseases incited by soilborne plant pathogens and parasites. While Mazzola has worked within the context of applied plant pathology and extending solutions to the community of agricultural producers, the broader vision encompassed by his studies have addressed both functional mechanisms involved in disease control and the effect of plant genotype on the efficacy of such practices.
Mazzola’s research program has focused on the function of microbial ecology in both the cause and control of soilborne diseases in tree fruit production systems. He is a world authority on tree fruit replant diseases and the development of nonfumigant, ecologically sustainable measures for their control. He is recognized for his contributions in resolving the etiology of apple replant disease and for pioneering multiple means for control of this disease that reduce dependence on soil fumigants. He used a simple, but elegant, approach to definitively establish that soilborne microorganisms are the dominant incitants of disease and to identify the responsible pathogen complex. These studies demonstrated that elements comprising the causal pathogen complex are consistent among divergent orchard sites, arguing against the assumption that the cause of replant disease varies even among orchards within close proximity. Mazzola garnered convincing evidence refuting reports that the disease was restricted to old orchard sites, demonstrating that a microbial community capable of inciting replant disease could develop within 3 years of orchard establishment and could be a significant impediment to productive nursery operations. The same approach has been adopted by various investigators to examine the etiology of replant disease in other hosts and regions of the world. These studies provided the long-elusive knowledge required to formulate and assess specific nonfumigant measures for control of replant disease in apple.
Mazzola is recognized for originating novel studies on the development of biologically based disease-control methods and for elucidating the underlying mechanism(s) responsible for disease suppression. His work on active manipulation of microbial communities through crop cultivation for soilborne disease suppression and the plant-genotype dependent nature in elicitation of this response was the basis for receiving the APS Lee M. Hutchins Award.
Mazzola completed definitive studies that challenged the broadly held presumption of a primary or exclusive role for glucosinolate hydrolysis products in pathogen and weed suppression attained in response to soil incorporation of Brassicaceae plant residues, commonly referred to as “biofumigation”. His studies demonstrated the necessity of an active soil microbial community to attain control of specific pests in response to Brassicaceae seed meal amendments and that the operative microbial entity and the functional mechanism(s) conferring suppression differed in a pest- and time-dependent manner. These findings have stimulated the study of non-glucosinolate-derived mechanisms of pest suppression by other scientific groups worldwide. Mazzola developed Brassicaceae seed meal formulations that demonstrate the ability to control the apple replant disease causal pathogen complex and improve tree growth and yield in a manner equivalent or superior to that attained in response to fumigation. He also demonstrated in large-scale commercial trials that, unlike preplant soil fumigation, the seed meal formulations stimulated the development of a microbial community that suppresses reinfestation of orchard soil by root pathogens, including Pythium spp. and Pratylenchus penetrans. The tree fruit industry, including organic apple growers, recognizes and has benefited from the advances Mazzola has made in solving the chronic apple replant disease problem.
Mazzola and associates conducted studies that documented, for the first time, existence of a sensing-signaling mechanism in bacteria–protozoa interactions that result in activation of an antipredator response in prey populations. It was found that cyclic lipopeptide (CLP) production by certain Pseudomonas fluorescens strains enhanced their survival in soil and the rhizosphere when challenged with the bacterivorous protozoan Naegleria americana. These studies demonstrated that altered bacterial gene regulation, including the up-regulation of CLP biosynthesis genes, did not require intimate contact with the amoeba predator.
During his career, Mazzola’s research achievements have been documented in 71 authored or coauthored peer-reviewed research articles and 12 book chapters, including three contributions to the Annual Review of Phytopathology. Because of his excellent research productivity and service to growers, Mazzola has received a USDA-ARS award annually since 1996 for outstanding or superior performance. Mazzola is most proud of his role in mentoring graduate students in multiple disciplines and institutions, including Washington State University, University of Idaho, Oregon State University, Sonoma State University, and Stellenbosch University. He has directed seven students to M.S. or Ph.D. degrees, served on the committees of 17 other graduate students, directed six post-doctoral scientists, and served as external examiner for Ph.D. students in Australia, Pakistan, and South Africa.
Mazzola has been active in service to professional societies. In addition to APS, he is a member of the American Society for Microbiology, the International Society for Microbial Ecology, and the Soil Ecology Society. He served on the APS Soil Microbiology and Root Disease Committee (1995–1998; chair, 1997). Mazzola served as an associate editor (1997–1999) and a senior editor (2000) for Phytopathology and on the Editorial Board of the journal Biological Control (2005–2010).
