In this study, the inhibitory effect of medicinal plant extracts viz., marigold (Tagetes spp.), rosemary (Rosmarinus
officinalis L.) and nigella (Nigella sativa L.) on root-knot nematode, Meloidogyne javanica @ 1500, 2500 and 5000
juveniles were studied on susceptible tomato cv. Karoon under greenhouse condition. Although all the treatments
reduced root infections rate and significantly effect on root weight (P ≤ 0.05). It was observed that when the
nematode inoculum increased, reproduction factor also increased while extract treatments effect decreased. In
between treatments, rosemary extract has the greatest impact on the reduction of nematode populations @ 40%
concentration as compared to control.