Abstract
Essential oils (EOs) have gained increasing interest as a low-toxic, eco-friendly alternative to synthetic repellents and insecticides against insect pests. However, they have scarce practical application in the protection of stored grain because of their limited efficacy and their interference with the organoleptic properties of the grain. In this study, we evaluated the olfactory profile of the EOs of Foeniculum vulgare, Pistacia lentiscus, and Ocimum basilicum, and their toxicity against the main stored grain pest Sitophilus granarius. Trained assessors identified O. basilicum and F. vulgare, as more suitable than the P. lentiscus EO for the wheat treatment. In laboratory tests, the most toxic EO was the P. lentiscus (LC50 = 36.36 μL∙kg−1) while, the least toxic, was the F. vulgare one (LC50 = 77.59 μL∙kg−1). The EOs were also tested combined with diatomaceous earths (DEs) showing synergistic effects (co-toxicity coefficient values ranging from 1.36 to 3.35 for O. basilicum and F. vulgare EOs, respectively). Overall, O. basilicum resulted as the best EO for the wheat treatment, considering its insect toxicity and olfactory profile. In real storage conditions, the wheat co-treated with O. basilicum EO and DEs showed a significantly lower mean infestation (1.5 insect kg−1) than the non-treated wheat (7.0 insect kg−1).
Highlights
Insects represent a serious threat for the stored food
The essential oils (EOs) of F. vulgare was purchased from KOS srl (Carmignano, PO, Italy); the EO of O. basilicum, methyl chavicol type, was purchased from Sigma-Aldrich (Milan, MI, Italy); the EO of P. lentiscus was purchased from Efit srl (Terni, TR, Italy)
P. lentiscus EO was characterized by a less appealing smelling profile in comparison with O. basilicum and F. vulgare EOs, whose properties are widely exploited in aromatherapy [34]
Summary
In cereals and pulses, insect pests cause direct damage by feeding on the seeds, and indirect damage by causing “pockets” of heat and moisture, in the mass of the stored grain. The control of foodstuff pests is based on synthetic insecticides and fumigants and poses questions about the food and environmental safety, in addition to the insurgence of insecticide resistance among pest populations [2] Alternative treatments, such as modified atmospheres, low temperatures, microbial insecticides, plant extracts, and inert dusts are currently of interest for the control of stored product pests, in compliance with the principles of Integrated Pest Management [3,4,5,6].
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