Biological control of root knot nematode (Meloidogyne javanica) through Trichoderma viride was investigated in greenhouse conditions. In comparison with the control, different concentrations of the spore of fungus (as treatments) decreased the disease level, egg mass production per plant and mean number of eggs per egg mass (P<0.05). Different concentrations of spore of antagonist decreased the disease level (gall numbers), but in concentration of less than 104 spore/ml there were no significant differences observed among treatments in egg mass production per plant, and at the concentrations of 104-107 spore/ml of the antagonist there were significant differences observed among treatments. There were significant differences among treatments (Trichoderma + nematode) in egg number per egg mass only at 102 spore/ml of antagonist. Trichoderma viride decreased disease level (gall size means) and mean number of egg mass per plant even after plant inoculation by the nematode. There were significant differences in number of egg mass production per plant and the number of eggs per egg mass at giant cells production stage (4 days after nematode penetration into the roots), but at the formation of the young adult stage of nematode (15 days after nematode penetration into the roots), only the number of egg mass production per plant was decreased. Maximum level of egg hatching (in control) was observed to be three days after incubation, while in treatments (Trichoderma + nematode) it was six days after incubation.
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