ABSTRACT
ABSTRACT Biological control of pathogens by introduced microorganisms has been studied since the mid-1940s, but has not been considered commercially feasible until recently. The surfaces of plant parts provide a habitat for epiphytic microorganisms, including pathogen and saprophytic organisms, as biological agents. The saprophytic organisms help to reduce the incidence of foliar disease. The activity of both saprophytes and pathogens on leaves is dependent on the microclimatological conditions at the plant surface as well as in the chemical environment. To be successful, the antagonist should be able to multiply on and colonize the plant surface. Biological agents act through various mechanisms, including substrate competition and niche exclusion, siderophores, antibiotics, and induced resistance, according to the relationship between biocontrol agents and pathogens or other microorganisms in the environment. Some studies have shown that biological agents such as Pseudomonas flourescens, Pseudomonas putida, and Bacillus subtilis reduced the severity of foliage bacterial diseases by 25%–92.5%.
