Studies were carried out to evaluate the repellent properties of the seeds of alligator pepper, <i>Aframomum melegueta </i>and Black pepper, <i>Piper guineense, </i>and ginger, <i>Zingiber officinale </i>rhizomes against <i>S. zeamais</i>. In 4-way olfactometry bioassays, <i>S. zeamais</i> adults showed strong attraction to maize and wheat seed volatiles but were significantly repelled by odours emanating from the seeds of <i>A. melegueta</i>, <i>P. guineense</i> and <i>Z. officinale</i> rhizomes. In field trials crushed <i>A. melegueta </i>seeds and <i>Z. officinale </i>rhizomes, significantly repelled <i>S. zeamais</i> from traditional maize granaries with treated maize cobs giving higher germination than untreated cobs. Laboratory reproductive potential studies showed that <i>A. melegueta </i>and <i>Z. officinale </i>powders caused significant adult mortality and reproductive potential deterrence against <i>S. zeamais</i> resulting in a reduction in F<sub>1</sub> progeny emergence. Olfactometer bioassays also confirmed that vacuum distilled <i>A. melegueta</i> and <i>Z. officinale </i>extracts and oleoresins were repellent towards adult <i>S. zeamais</i> when tested alone, and in combination with maize grains. Bioassay-guided liquid chromatography of the distillates showed that fractions containing polar compounds accounted for the repellent activity. Coupled gas chromatography-mass spectrometry (GC-MS), followed by GC peak enhancement and enantioselective GC using authentic compounds, identified 3 major compounds in the behaviourally active <i><span style='text-transform:uppercase'>A. melegueta </i>fraction to be (<i>S)</i>-2-heptanol, (<i>S)</i>-2-heptyl acetate and (<i>R)</i>-linalool in the ratio 1:6:3. <i>Z. officinale</i> had 1,8-cineole, neral and geranial in the ratio of 5.48:1:2.13. The identification of these behaviourally active compounds provides a scientific basis for the observed repellent properties of <i><span style='text-transform:uppercase'>A. melegueta </i>and <i>Z. officinale </i>extracts, and demonstrates the potential for their development in stored-product protection at the small-scale level in Africa.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:499738 |
| Date | January 2008 |
| Creators | Ukeh, Donald A. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=25167 |
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