Encapsulation of sea fennel (Crithmum maritimum) essential oil in nanoemulsion and SiO2 nanoparticles for treatment of the crop pest Spodoptera litura and the dengue vector Aedes aegypti

Crithmum maritimum L. (Apiaceae), also known as sea fennel, is a halophythe plant colonizing cliffs and coastal dunes and pebble of the Mediterranean sea and Atlantic ocean. Based on previous reports, this herb produces an essential oil endowed with insecticidal effects against various pests and insect vectors. In the present work, we investigated the insecticidal effectiveness of the seed essential oil and its encapsulated forms (nanoemulsion and SiO2 nanoparticles, SiNPs) against larvae of the mosquito Aedes aegypti and cotton leafworm Spodoptera litura, in terms of larval contact toxicity and reduction of adult longevity and fecundity. The essential oil composition was characterized by the phenylpropanoids dillapiole and myristicin and oxygenated monoterpenes γ-terpinene and thymol methyl ether. Based on the insecticidal assays, we noticed that all developed products, namely sea fennel essential oil, nanoemulsion and encapsulated silica nanoparticles, showed significant toxicity against larvae and pupae of Ae. aegypti and S. litura. Notably, the SiNPs showed LC50 values ranging from 8.823 (I instar) to 17.911 μL/L (pupa) on Ae. aegypti (I instar-pupa) and from 24.610 (I instar) to 64.546 μL/L (pupa) on S. litura. Furthermore, all three selected bioinsecticides reduced longevity and fecundity in both targets. Overall the sea fennel essential oil and its encapsulated forms, i.e. nanoemulsion and SiNPs, are promising alternatives for the control of insects causing human diseases and damages in agriculture.