Andean Plants Essential Oils: A Scented Alternative to Synthetic Insecticides for the Control of Blowflies.

Blowflies are vectors of microorganisms and human pathogens, and their maggots cause myiasis in vertebrates and infest and spoil meat and fish products. Essential oils (EOs) from spices were proven to be a safer and more sustainable alternative to synthetic insecticides for the control of blowflies and are suitable for protecting food from such pests. However, some EOs are not acceptable for environmental or topical applications due to their strong, unpleasant odour. In this study, we measured the acute toxicity and the repellence of two EOs extracted from the Andean plants Palau and (Kunth) Triana and Planch., both known for their pleasant odour, against the blue blowfly (L.) (Diptera: Calliphoridae). We also compared their bioactivity with that of the L. EO, which is very effective but bad-smelling. The EO was mainly rich in oxygenated monoterpenes, the most abundant of which were geranial (26.8%) and neral (21.0%). The EO was chiefly composed of monoterpene hydrocarbons, mostly represented by limonene (46.2%). According to the sensory description, the best odour profile was associated with the EO, while the olfactory expression of the EO from was negatively affected by a strong odour of "mouldy lemon". The behavioural test showed that the EO was more repellent than that of and, on the contrary, that the EO was attractive. The toxicity tests showed that the EOs of both Andean plants have a clear toxic effect on the eggs and adults. In terms of ovicidal activity, there were no significant differences among the effects of the three tested EOs. On the adult flies, the toxicity of the two EOs of the Andean plants was much lower than that of (LC fumigation = 1.86 μL EO L air; LC ingestion = 8.10 μL EO mL gel) both by fumigation (LC = 23.66 and 25.30 μL EO L air for and respectively) and ingestion (LC = 36.65 and 44.97 μL EO mL gel for and respectively), while, by contact, the EO (LD = 0.27 μL EO insect) was more toxic than the EO (LD = 0.46 μL EO insect).