This study developed and evaluated the toxicological effects of new stable nanoemulsions (NEs) of peppermint essential oils (EOs) and palmarosa EO + linalyl acetate (LA) using ultrasound cavitation. Moreover, the study analyzed the effect of LA in the stabilization process of palmarosa NEs. Peppermint NEs had sizes of 34 nm and polydispersity index (PDI) values of 0.424, whereas palmarosa NEs showed sizes of 15 nm and a PDI of 0.078. Peppermint NEs were stable for 30 days and palmarosa NEs for 120 days. The insecticidal effect of NEs was also evaluated against Cx p. pipiens and Plodia interpunctella larvae. In Culex pipiens pipiens, the LC 50 values were 31.24 ppm for peppermint NEs and 32.30 ppm for palmarosa + LA NEs. In P. interpunctella, the NEs were combined with βcypermethrin and the LC 50 values were 0.12 μg larvae −1 for peppermint NEs and 0.23 μg larvae −1 palmarosa + LA NEs. In addition, the NEs showed no toxicity effect in nontarget organisms such as Artemia salina and Tenebrio molitor. Finally, viability on mammalian cell culture models was evaluated and it was also observed that NEs did not affect the cell viability after 3 and 7 days of exposure.

Mosquitoes (Diptera: Culicidae) are vectors of important parasites and pathogens causing death, poverty and social disability worldwide. The overuse of synthetic insecticides to control mosquito vectors lead to resistance, adverse environmental effects and high operational costs. Therefore, the development of eco-friendly control tools is an important public health challenge. In this study, two different essential oils (EO) (geranium, Geranium maculatum, and bergamot, Citrus bergamia) loaded polymeric nanoparticle (PN) were elaborated using polyethylene glycol (PEG) and chitosan (Qx) as the polymeric matrix/coating. In addition, the mosquito larvicidal acute and residual activity of the PN was evaluated on Culex pipiens pipiens. The physicochemical characterization of PN revealed that PEG-PN had sizes <255 nm and encapsulation efficiency between 68 and 77%; Qx-PN showed sizes <535 nm and encapsulation efficiency between 22 and 38%. From the toxicological test, it was observed that Qx-PN produced higher acute and residual activity than PEG-PN. Overall, this study highlights that polymer nanoparticles containing essential oil are a promising source of eco-friendly mosquito larvicidal products.

Essential oils (EOs) have been recognized as an important source of biopesticides. This work investigated the chemical constituents and bioactivity of six essential oils namely lavender (Lavandula angustifolia Mill.), peppermint (Mentha piperita L.), geranium (Geranium maculatum L.), palmarosa (Cymbopogon martinii (Roxb.) Wats), eucalyptus (Eucalyptus globulus Labill.) and bergamot (Citrus bergamia Risso) against adults of the Indian meal moth, Plodia interpunctella, a cosmopolitan pest that infests a wide range of stored products. Analysis by gas chromatography coupled to mass spectrometry (GC-MS) revealed the presence of several compounds, mainly mono-and sesquiterpenes. The contact toxicity assay showed that the EO from palmarosa was the most toxic with a LD50 value of 22.8 µg cm-2. The toxicity order was palmarosa > geranium > peppermint > lavender > bergamot >eucalyptus. In fumigant toxicity assay, the greatest effect was found with the EO from eucalyptus with a KT50 value of 8.34 min. The toxicity order was eucalyptus > peppermint >geranium = lavender > bergamot > palmarosa. The EO from palmarosa showed the highest residual activity when the insects were exposure to its volatiles constituents. Finally, all EOs produce sublethal activity promoting effects in the fecundity. In conclusion, the EOs could be used as potential biopesticides for P. interpunctella control.

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One of the most common insect pests is Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae), which affects different food commodities. A new effective approach for the management of insect pests is the development of new formulations based on essential oils (EO). However, few works informed about the relationship between insecticidal activity of EO or essential oils loaded polymeric nanoparticles (EOPN) and post-application temperature. In our work, palmarosa [Cymbopogon martinii (Roxb.) Watson], geranium (Geranium maculatum L.), and peppermint (Mentha piperita L.) oils were formulated in a polyethylene glycol 6000 matrix to obtain EOPN. Geranium and palmarosa EOPN had sizes of 259 and 191 nm, respectively; the encapsulation efficiency (EE) was close to 90%, and the samples were monodisperse. The sizes from peppermint EOPN were around 380 nm, with an EE of 72%, and were polidisperse. In a contact toxicity bioassay, the insecticidal effect of the oils was increased by all EOPN, with palmarosa oil being the most toxic. In addition, the oils and their nanoparticles showed a significantly negative temperature coefficient when applied by contact. In a fumigant bioassay, just palmarosa and peppermint EOPN enhanced the oil activity and palmarosa EO and EOPN showed the highest toxic effect. In this case, the EO and EOPN insecticidal activity was unaffected by environmental temperature variation.

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