The study examined the repellency of Gardenia jasminoides ethanol-extracted oil against the German cockroach, Blattella germanica, and the pharaoh ant, Monomorium pharaonis, which are serious pests in areas of public health hygiene. For the repellency tests, 31.4 μg of the oil was applied per cm2 on one half of filter paper discs (9 or 15 cm diameter for the ant and cockroach, respectively), whereas the other half was treated as control (DMSO + Tween). Repellency effects were observed 1, 2, 3 and 4 h after the insect release. The oil showed high repellency against all life stages of cockroaches and worker ants. The maximum repellency was observed for the cockroach adults (81.7 ± 3.1%) followed by the fourth, third and second nymphal stages (76.7 ± 4.2, 75.0 ± 3.4, and 56.7 ± 8.4%, respectively), after 1h exposure. The repellence effect was strong against worker ants (78.3 ± 4.8%) after 1 h exposure. The repellence effect can last at least four hours for both species. Analysis of Gardenia oil with Gas chromatography-mass spectrometry identified 14 major chemical components.
