ABSTRACT
Inoculation of soil with a single strain of biocontrol agent only rarely leads to a level of protection obtained with chemicals and a positive effect is often inconsistent. The way to improve plant bioprotection may be the use of mixtures or combinations of biological agents, especially when they exhibit different or complementary modes of action. Pierson and Weller showed that combining strains of fluorescent pseudomonads increased control of wheat take-all compared to the same strains applied individually. There was a general trend in all experiments toward greater suppression and enhanced consistency against the pathogens using strain mixtures. Negative interactions between introduced agents and between agents and indigenous microflora can influence their performance in soil. Competition for nutrients or a detrimental effect of secondary metabolites produced by one organism on the growth of the other was reported as the cause of the mutual suppression.
