Securidaca longepedunculata Fers (Polygalaceae) is commonly used as a traditional medicine in many parts of Africa as well as against a number of invertebrate pests, including insects infesting stored grain. The present study showed that S. longepedunculata root powder, its methanol extract, and the main volatile component, methyl salicylate, exhibit repellent and toxic properties to Sitophilus zeamais adults. Adult S. zeamais that were given a choice between untreated maize and maize treated with root powder, extract, or synthetic methyl salicylate in a four-way choice olfactometer significantly preferred the control maize. Methyl salicylate vapor also had a dose-dependant fumigant effect against S. zeamais, Rhyzopertha dominica, and Prostephanus truncates, with a LD100 achieved with a 60microl dose in a 1-l container against all three insect species after 24 hr of exposure. Probit analyses estimated LD50 values between 34 and 36 microl (95% CI) for all insect species. Furthermore, prolonged exposure for 6 days showed that lower amounts (30 microl) of methyl salicylate vapor were able to induce 100% adult mortality of the three insect species. The implications are discussed in the context of improving stored product pest control by small-scale subsistence farmers in Africa.

Securidaca longepedunculata Fers (Polygalaceae) is commonly used as a medicine in many parts of Africa and shows promise for protecting stored grain against insect pests. Analysis of a methanol extract of the root bark by gas chromatography linked to mass spectrometry (GC/MS) showed a major component accounting for over 90% of the volatile material. This was identified as methyl 2-hydroxybenzoate (methyl salicylate) by comparison of the GC retention times and mass spectrum with those of synthetic standards. This conflicts with an earlier report that the major component is methyl 4-hydroxybenzoate. Two minor components had mass spectra characteristic of 2-hydroxybenzoate esters and were identified as methyl 2-hydroxy-6-methoxybenzoate and its benzyl analogue, again conflicting with an earlier report.

The plant Securidaca longipedunculata is known to have various ethnopharmacological and pesticidal properties, including its indigenous use by small-scale African farmers for stored product pest control. This paper reports the results of a study involving 4 stored-grain insect pest species, Sitophilus zeamais, Rhyzopertha dominica, Callosobruchus maculatus, and Prostephanus truncatus, which showed that the powdered root of Securidaca longipedunculata (collected from Tamale, Ghana) admixed with commodity at 0.5% w/w was effective at reducing the F1 emergence of all 4 species when compared with untreated commodity trials. A methanol extract of Securidaca longipedunculata roots sprayed on commodity at 0.1% w/w was equally effective at reducing F1 emergence compared with the control. Bioassay-guided fractionation of the methanol extract showed that the most polar compounds in the roots were responsible for the reduction of live adults in the F1 generation. The implications of these results are discussed in the context of isolating and characterizing biologically active compounds with a view to improving stored-product pest control by small-scale farmers in developing countries.