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Insecticidal activity evaluation of Persea venosa Nees & Mart. essential oil and its nanoemulsion against the cotton stainer bug Dysdercus peruvianus (Hemiptera: Pyrrhocoridae) and pollinator bees

Abstract:

Cotton is one of the most significant commodities in the whole world, so the protection of this kind of crop against pest insect infestations is essential. This work aims to evaluate the insecticidal potential of the essential oil of the leaves of Persea venosa Nees & Mart. and its nanoemulsion against the cotton stainer bug. Fresh leaves of P. venosa were submitted to hydrodistillation and analyzed by gas chromatography (GC) coupled to a mass spectrometer (MS). The plant species presented the substance β-caryophyllene, Caryophyllene oxide, α-humulene, and α-copaene as the major compounds, comprising 43.78 %, 8.92 %, 8.27 % and 5.90 % of the essential oil, respectively. The nanoemulsion was obtained by low energy input, using the phase inversion method, generating a nanoemulsion with a particle size of 68.41 nm. The insecticidal assays were conducted to evaluate the lethality and sub-lethal damages at the cotton-stainer-bug. The essential oil and nanoemulsion presented LD50 of 24.45 μg/µL and 28.73 μg/µL respectively. Pure oil and the dilution at a concentration of 450 μg/µL caused 100 % mortality of the insects on the first day. An assay was performed with β-caryophyllene, which also showed 100 % mortality on the first day of treatment, indicating that the major substance could be responsible for insect mortality. The nanoemulsion showed 55 % of mortality after 20 days. Delays in insect development were observed in all samples tested. The essential oil showed selectivity to D. peruvianus by not causing significant harm to Apis mellifera and Partamona helleri. This research shows promising feasibility results for producing a nanoemulsified essential oil with selective insecticidal activity to control a pest of agricultural importance.