ABSTRACT

Soils where plant disease incidence is low, even when the pathogen is present in high numbers, or disease-suppressive soils, were ¤rst described in the late 1800s (Huber and Schneider 1982), and the biological nature of this phenomenon was documented in the 1950s (Menzies 1959). Since then, researchers have been working to understand the nature of this interaction between a host plant, a pathogen, and the surrounding microbial communities, so that agricultural soils can be managed in a way that encourages suppression of disease (Curl 1988; Whipps 2001; Mazolla 2002; Sánchez-Moreno and Ferris 2007). The original conceptual underpinnings of the modern organic agriculture movement include an emphasis on maintaining soil organic matter to support biologically-based soil and plant health (Howard 1943, 1945). Among the numerous available methods for managing soil organic matter are the practices of cover cropping and addition of organic materials from external sources, that is, compost or vermicompost amendments. In addition to increasing soil organic matter, the highly diverse micro¯ora of composts and vermicomposts can suppress plant diseases when used as soil amendments. Disease-suppressive

CONTENTS

I Introduction .................................................................................................. 165 II The Role of Earthworms in Suppression of Soilborne Plant Diseases ......... 167 III Suppression of Plant Pathogens with Vermicompost Amendments ............. 168 IV Conclusions and Directions for Future Research ......................................... 175 References .............................................................................................................. 177

composts and vermicomposts have been well documented in the scienti¤c literature (see reviews by Hoitink and Fahy 1986; Weltzien 1989; Hoitink et al. 1991; Litterick et  al. 2004); however, the use of compost for disease management is plagued by inconsistency in practice. Only relatively recently have earthworms and vermicomposts been investigated for their ability to suppress plant disease. This Chapter reviews the current state of knowledge on the roles of earthworms and vermicomposts in biologically based plant disease management and points out directions for future research efforts.