Population dynamics of biocontrol agents and pathogens in soils and rhizospheres

Understanding the dynamics between a pathogen and a biocontrol agent (BCA) in soil or in an infection court such as the rhizosphere is crucial for pre dicting the success of biological control. This is especially true for biol ogical control using the strategy of reduction of initial inoculum prior to infection. By studying the population density fluxes over time, one can ob serve how the BCA and pathogen influence each other's population and life c ycles, and how the biological and physical environment influence this relat ionship. Methods for quantifying fungi and bacteria in soil, including clas sical (dilution plating, baiting, bioassays), immunological (ELISA, IFC, im munomagnetic) and molecular (DNA hybridization, PCR, marker and reporter ge nes) methods, are discussed and critiqued. Finally, the value of mathematic al modeling of population dynamics as a means of providing important inform ation about the tripartite relationship between the pathogen, BCA, and host plant is reviewed.