Root-knot nematode disease caused by Meloidogyne incognita (Kofoid and White) Chit wood) is one of the major
constraints for successful cultivation of tomato (Lycopersicon esculentum Mill.) in Ethiopia. Hence, the present study
was conducted to evaluate the effect of leaf and seed extracts of four botanicals viz., Rape seed (Brassica napus
L.), Lantana (Lantana camara L.), African marigold (Tagetes erecta L.) and Neem (Azadirachta indica L.) at 5% and
10% concentrations and T. harzianum at 5% plus control were tested on root-knot nematode under in vitro and also
to evaluate their against root-knot nematode development and their role on plant growth parameters of tomato under
in vivo condition. Plant extracts were more effective and significantly inhibited egg hatching and immobilizing the J2
larval mortality of M. incognita than T. harzianum. Aqueous extract of all the tested plants inhibited egg hatching of
nematode and resulted 84.67-100% mortality of the J2
juveniles of M. incognita in vitro at the 10% concentration after
72 h of exposure time. There were no significant differences among the treatments of rape seed leaf (84.7%) at 10%
concentration and Lantana camara (87%), African marigold (86.3%) and Neem leaf (85%) at 5% concentration after
72 h. Aqueous seed extracts of A. indica more significantly inhibited egg hatching and larva mortality of the J2
of M.
incognita in vitro at the 10% concentration and immobilized by 89, 93 and 100% after 24, 48 and 72 h of exposures,
respectively, while at similar concentration of T. erecta, B. napus and L. camara leaf extracts exhibited 92, 89 and
93.2% inhibition of egg hatching and 75, 62.1 and 73% larval mortality, respectively. The effect of different botanicals
and T. harzianum singly and in combination were studied for the management of tomato root-knot nematode under
greenhouse condition. There was a significant difference in the reduction of root-knot nematode incidence, root-knot
nematode population, nematode reproduction rate (NRR), number of galls and egg masses per plant were recorded.
In pot culture condition, the application of leaf extract of individual plant in the presence of the nematode significantly
enhanced the growth of tomato seedlings in comparison to the control. A significant increase in plant height, shoot
weight and root weight of the seedlings were observed at the 10% concentration of leaf extracts in comparison to
control. There was a significant difference in the reduction of root-knot nematode population, nematode reduction
rate, number of galls and egg masses per plant of L. camara combined with T. harzianum. The mean fruit weight
and total yield were observed highest in the combination treatment of L. camara combined with T. harzianum. This
study results revealed that the test plants are readily available to farmers at no cost and able to reduce nematode
population below economic threshold.