Behavioral and toxicological effects of monoterpenes on Triatoma infestans

MORETTI AN; ZERBA EN; ALZOGARAY RA

Huerta grande, Córdoba

Encuentro; Second Meeting of the Latin American Association of Chemical Ecology; 2012

Asociación Latinoamericana de Ecología Química

Some essential oils have been used against plagues since millennia. They are complex mixtures of monoterpenes, phenols and sesquiterpenes, both safe to non-invertebrate organisms and environment. Monoterpenes have a broad spectrum of insecticidal activity, in which triatomines are already included. This work belongs to a project focused in the development of new diagnostic and control tools for Chagas disease. First instar nymphs of Triatoma infestans, main vector of Chagas in Argentina, were exposed to: carvacrol, (-)carveol, citronellol, eugenol, geraniol, linalool, menthol, á-terpineol or thymol. To evaluate the effect on locomotor activity, groups of four nymphs were allowed to walk on filter papers impregnated with acetone solutions of each substance and recorded with a video camera connected to an image analyzer. Deltamethrin was used as a positive control (it produced hyperactivation from 0.39 µg/square cm). All monoterpenes produced hyperactivity from 390 or 3,900 ìg/ square cm. The knock-down effect was evaluated in plastic containers with lids. Groups of ten nymphs were exposed to filter papers impregnated with acetone solutions of the substances at 3,900 ìg/ square cm. The number of knocked-down insects was recorded every ten minutes. Replicates were interrupted when 90% of the insects were knocked-down or 7 hours after the start of the exposure. Values of Knock-down Times for 50% of the exposed insects (KT50) were calculated. Dichlorvos, a volatile organophosphate, was used as a positive control. Dichlorvos was significantly more toxic than any other substance and monoterpenes presented this order of toxicity: a-terpineol < eugenol < carvacrol < linalool < thymol. (-)-Carveol, citronellol, geraniol and menthol exceeded the 7 h of exposure with less of 50% of the insects knocked-down. In the immediate future we planned to assess the ability of these monoterpenes to produce flushing-out effect on semi-field and field conditions. Thymol and linalool are worthy of further study as potential active ingredients of triatomicides formulations.