The Dysdercus peruvianus Guérin-Méneville is commonly known as the cotton stainer bug. In this study, it was evaluated the insecticide activity and mode of action of the essential oil from leaves of Ocotea elegans Mez and its nanoemulsion against D. peruvianus. Leaves of O. elegans were extracted by hydrodistillation. The essential oil obtained was analyzed by gas chromatography coupled with electron impact mass spectrometry and flame ionization detector. The essential oil toxicity measured by lethal dose 50 (LD50) and survival rate of insects were recorded. Lastly, an assay was carried out to assess the inhibition of the enzyme acetylcholinesterase to determine a possible mechanism of action of insecticidal activity. The sesquiterpene sesquirosefuran was the major compound detected and corresponds to 92% of the components of the essential oil. The nanoemulsion more stable showed hydrophilic lipophilic balance (HLB 11.74), droplet size 92±1.80 nm, and polydispersity index (PDI of 0.215±0.015). After the topical application of the O. elegans essential oil, significant decreases in the survival of D. peruvianus occurred in a dose-response manner with LD50 = 162.18 μg and the survival rate of the nanoemulsion in D. peruvianus was 10.0±5.47, a better value than in pure essential oil. The acetylcholinesterase inhibition presented inhibition concentration (IC50 = 1.37mg/mL) and mixed type of inhibition. This indicates that the essential oil of leaves from O. elegans and its nanoemulsion are promising candidates for use in integrated pest management programs.

As the second most common infectious parasitic disease in the world, schistosomiasis is present in Brazil, mainly in the Northeast and Southeast regions. Currently, the recommended form of prevention is controlling this disease’s intermediate host, mollusks of the Biomphalaria genus, using the chemical molluscicide Bayluscide WP 70^®. This synthetic molluscicide is expensive, has low selectivity for Biomphalaria glabrata species, and is toxic to the environment. In this context, the use of natural products such as molluscicides represents a sustainable control method. The objective of this study was to evaluate the molluscicidal effects of a crude ethanolic extract of the leaves and stems and fractions of the species Myrsine parvifolia on the mollusk Biomphalaria glabrata. Methods: The methodology was adapted from standards defined by the World Health Organization (WHO), where the molluscicidal activity of Myrsine parvifolia was investigated as an alternative for the population control of Biomphalaria glabrata and That’s right. environmental toxicity was evaluated using the Physella sp. The results revealed that the stem ethanolic crude extract exhibited activity after 24 h of exposure, with an LC₅₀ of 207.4 mg/L and an LC₉₀ of 256.2 mg/L. Conclusions: Myrsine parvifolia can be used as a sustainable biological alternative for the population control of Biomphalaria glabrata snails, especially for poor populations and inaccessible regions.