To fully evaluate the potential of a biological control agent, a dose–response relationship between the concentration of the applied antagonist applied and the reduction of plant damage needs to be established. However, the inoculum density of the antagonist is difficult to determine in the kind and amount necessary for optimal activities. Different studies on antagonist dose–plant disease response relationships in biological control systems have been reported (Montesinos and Bonaterra, 1996 and Smith et al., 1997). Some studies on the effects of different inoculum densities of Trichoderma against Meloidogyne spp. have demonstrated an increase in their efficacy at increasing inoculum density but up to certain levels ( Jindapunnapat et al., 2013 and Sahebani and Hadavi, 2008).
The purpose of this study was to evaluate the effects of four inoculum densities of two local (Saudi) isolates Trichoderma harzianum (isolate-27) and Trichoderma viride (isolate-08) on their biocontrol efficacy against Meloidogyne javanica on tomato.