Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 36: 2346 - 2352. Published December 7, 2010.
Effect of botanical extracts on root-knot nematode (Meloidogyne incognita) infection and growth of cacao seedlings
Okeniyi, M. O1., Fademi O. A1., Orisajo, S. B1., Adio S.O1 .,Otunoye, H. A1. and Adekunle, O. V2.
1Crop Protection Division, Cocoa Research Institute of Nigeria, Ibadan, Oyo State, Nigeria.
2Olabisi Onabanjo University, Ago-Iwoye, Ogun State, Nigeria
Corresponding author e-mail: michael_okeniyi@yahoo.co.uk
ABSTRACT
Objectives: To determine the effects of Bridelia micrantha, Mallotus oppositifolius, Hunteria umbellata and Citrus medica leaf extracts on growth and root-knot infection caused by M. incognita on cacao.
Methodology and results: The effect of four rates (0, 10, 25, 50 and 100%) of leaf extracts was tested. Water extract of all the test plants significantly inhibited egg hatching of nematode and caused 100% mortality of the second juveniles of M. incognita in vitro after 12h of exposure. Undiluted crude leaf extracts of H. umbellata and M. oppositifolius exhibited 100% inhibition of egg hatch and larva mortality, while undiluted leaf extracts of B. micrantha and C. medica 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 dilution of all the extracts. Juvenile mortality increased corresponding to an increased time of exposure. The leaf extracts of individual plant significantly enhanced the growth of cacao seedlings in the presence of the nematode in the nursery when compared to the control (p<0.05). There was a significant increase in plant height (68.2, 70.2, 65.9 and 65.7 for Bridelia micrantha, Mallotus oppositifolius, Hunteria umbellata and Citrus medica respectively), shoot weight and root weight of the seedlings treated with all the leaf extracts even at the lowest concentration of 10% compared to the rest.
Conclusion and application of results: This study showed that the test plants which are readily available to farmers at no cost have the ability to reduce nematode below economic threshold, thus this finding is important from the point of view of controlling root-knot nematodes affecting cacao seedling without the use of nematicides in view of the environmental pollution likely to cause. Farmers are therefore advised to apply the undiluted crude extract of the plants to cacao plants after transplanting to field as plant-parasitic nematodes have been implicated for poor seedling establishment. There is need for further studies in identifying new classes of pesticides from natural plants to replace the synthetic dangerous and expensive chemicals used at present.
Key words: Cacao seedlings, leaf extracts, Meloidogyne incognita, egg hatching, larval mortality
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