Studies were carried out to determine the microorganisms associated with Jatropha curcas and the effect of selected botanicals crude extracts (bitter leaf: Vernonia amygdalina and Uziza leaf: Piper guineensis) on the inhibition of these microorganisms. The experiment comprised three extract concentrations 20, 30 and 50% and was carried out in a completely randomized design with six replications. Results show that only Rhizoctonia sp., Fusarium oxysporum, Septoria apii and Aspergillus sp. were isolated from seeds and leaves of J. curcas. P. guineensis leaf extract, at 50% concentration, inhibited the growth of these organisms (94%) more than the bitter leaf (V. amygdalina) extract (80%) and similar trend was observed at all levels of concentrations. The high level of microbial inhibition obtained from the P. guineensis on J. curcas would be very useful information in the production of pesticides or fungicides combinations as their effectiveness is higher when combined than when singly applied. It was observed that higher percentage germination was recorded on healthier Jatropha seeds than diseased ones and only Fusarium solani and S. apii were isolated from leaf samples of J. curcas while Rhizoctonia spp. and Aspergillus spp. were isolated from the seed samples that showed characteristic rot appearance. However, few organisms observed in J. curcas showed that the crop does not provide conducive environment for the growth of many microorganisms, and as such possess fungicidal properties.
Key words: Micro-organisms, inhibition, selected, natural plants, Jatropha curcas.
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