Abstract

Root-knot nematode, Meloidogyne incognita (Kofoid and White) Chit wood) is one of the major constraints for the successful cultivation of tomato (Lycopersicon esculentum Mill.) in Ethiopia. Among different management strategies, biological control is important in the light of increased awareness of environmental and human health hazards. Therefore, the present study was conducted to evaluate the effect of different locally available botanicals and an antagonistic fungus, Trichoderma harzianum to control root-knot nematode attacking tomato under in vitro condition. 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 two different concentrations (5 ml and 10 ml) and Trichoderma harzianum (5 ml) were tested. Plant extracts were more effective and significantly inhibited egg hatching and immobilizing the J₂ larval mortality of M. incognita than T. harzianum. Aqueous extracts of all the botanicals inhibited egg hatching of nematode and resulted in 84.67 - 100 % mortality of the second juveniles of M. incognita at the 10% concentration after 72 h of exposure time. Leaf extracts of T. erecta and A. indica exhibited 100% inhibition of egg hatch and larva mortality, while at similar concentration of B. napus and L. camara leaf extracts exhibited 92 and 93.2% inhibition of egg hatch and 62.1 and 73% larval mortality, respectively. Egg inhibition and larval mortality decreased with increase in the dilution (10 ml) of extracts. Juvenile mortality increased corresponding to an increased time of exposure. Aqueous seed extracts of A. indica more significantly inhibited egg hatching and larva mortality of the J₂ of M. incognita at 10% concentration and immobilized by 89, 93 and 100% after 24, 48 and 72 h of exposures, respectively, This study revealed that the test plants are readily available to farmers at no cost and able to reduce nematode population below economic threshold. There is a need for further studies in identifying new classes of bio-pesticides from natural plants to replace the synthetic chemicals used at present.

Key words: Botanical leaf extracts, egg hatching, larval mortality, root-knot nematode, Trichoderma harzianum.