Associated microorganisms significantly influence plant diseases regarding inhibition and acceleration of the infection process. The root-knot nematode (N), Meloidogyne incognita complex with the root-rot fungal disease is an example of a disease complex that requires the collaboration of multiple pathogens to induce epidemic infection [(Pythium debaryanum (P), Fusarium solani (F) and Rhizoctonia solani (R)]. The disease complex is a significant problem due to the various interwoven diseases and the difficulties of using conventional approaches to control. Therefore, the study intended to introduce Virkon S as a nontraditional, non-selective, and non-persistent chemical sterilant agent for concurrent application with the multifunctional Trichoderma viride (T) bioagent. Based LC₅₀ values tested by the poisonous medium technique after three days of incubation showed T bioagent had the highest tolerance to Virkon S (0.491 % w/v), while the R pathogen was the most sensitive to Virkon S (0.385 % w/v), followed by F (0.457 % w/v), and finally P (0.487 % w/v). Diseases caused by P, F, and R are ranked from most incidence to most severe on tomatoes. Applying T bioagent decreased disease significantly varied with pathogen accompanied by enhancing tomato growth parameters infected with whether nematode or pathogenic fungi. Conversely, the bioagent T successfully reduced fungal disease incidence and severity and the final nematode population in tomato roots and soils resulting from the complex infection of the nematode and fungi and varied considerably according to tested fungi with the least efficiency in PNT treatment. Moreover, applying Virkon S with T bioagent against the nematode-fungi disease complex enhanced plant growth parameters enhancement exceeded healthy plants to reach a maximum increase with NTR treatment supplemented with 1.5 % (w/v) Virkon S. While 1.5 and 3 % (w/v) Virkon S concentrations completely suppressed nematode parameters except for PNT treatment. 
Our findings indicate that combining the Virkon S with T. viride results in preliminary control of the root-knot nematode-root rot fungi complex. Virkon S effectively suppresses the nematode population. Then, T. viride bioagent completes the march after the Virkon S's success in its mission and degrades in the soil. So that the Trichoderma parasite on the root rot fungi can colonize the rhizosphere region, enhancing tomato growth parameters significantly. This combination represents a new strategy against root-knot nematodes and the soil-borne fungus disease complex.