Bioactivity of the Andean aromatic plants Aloysia citriodora and Bursera graveolens essential oils against the blowfly Calliphora vomitoria

Tropical Andes is a biodiversity hot spot rich in aromatic plant species, whose potential as a source of active compounds for insect pests’ control is still largely underexploited. Here, the Essential Oils (EOs) extracted from two Ecuadorian plants, the shrub Aloysia citriodora (Verbenaceae) and the tree Bursera graveolens (Burseraceae), were chemically analysed and tested for their bioactivity against the blue blowfly Calliphora vomitoria (Linnaeus, 1758) (Diptera: Calliphoridae). This fly is a vector of pathogenic microorganisms, dangerous in factories and stores where fresh meat is processed, stored, and sold. The main components of the A. citriodora EO are geranial and limonene, while in the B. graveolens EO they are limonene and α-terpineol. The effects of the two EOs were evaluated against C. vomitoria by a behavioural assay in a two-choice olfactometer (concentrations range 0.07-2.8 μL L-1 air). Besides, the insecticidal properties of the two EOs were tested by fumigation (EOs concentrations from 6.06 to 36.36 μL L-1 air), by contact with topical applications using a Burkard micro dispenser (EOs dose from 0.10 to 0.60 μl EO/fly), and by ingestion of a mucilage containing EOs (from 15 to 75 μl EO mL-1 mucilage), sucrose, and agarose. Furthermore, the ovicidal activity was assessed (concentrations from 0.006 to 0.075 μL EO cm-2 of filter paper). The results of the behavioural assay showed a stronger repellent effect exerted by the A. citriodora EO, while all the toxicity tests revealed dose-dependent mortality of the blowflies and eggs.