Chairs’ Perspectives on Biological Control and Epidemiology

Abstract

The work presented here on biological control focuses primarily on the mechanisms by which effective control can be achieved. Thus, direct antagonism can be due to excretion of bactericidal thiophenes by roots of French marigolds (Terblanche and de Villiers), or of an irutin-related compound produced by Bacillus subtilis (Ciampi et al.). The presence of siderophore-like receptors may account for the efficiency of Pseudomonas fluoresceins spp at trapping any available soil iron to the detriment of pathogens (Ciampi et al). Competition for vascular colonisation of xylem vessels and induction of host resistance by Hrp^- mutant strains was also presented (Trigalet et al.; Saddler et al.). Whatever the mechanism(s) involved (direct and/or indirect antagonism) it now appears that survival of the antagonistic bacteria in field conditions may be greatly improved when the protective inoculum is inoculated in a carrier matrix (alginate beads, clay microgranules), and the greater the survival of the protective inoculum, the higher the protection achieved (Ciampi et al.; Trigalet et al.).