BackgroundPlants have been recognized as a good source of insecticidal agents, since they are able to produce their own defensives to insect attack. Moreover, there is a growing concern worldwide to develop pesticides with low impact to environment and non-target organisms. Hexane-soluble fraction from ethanolic crude extract from fruits of Manilkara subsericea and its triterpenes were considered active against a cotton pest (Dysdercus peruvianus). Several natural products with insecticidal activity have poor water solubility, including triterpenes, and nanotechnology has emerged as a good alternative to solve this main problem. On this context, the aim of the present study was to develop an insecticidal nanoemulsion containing apolar fraction from fruits of Manilkara subsericea.ResultsIt was obtained a formulation constituted by 5% of oil (octyldodecyl myristate), 5% of surfactants (sorbitan monooleate/polysorbate 80), 5% of apolar fraction from M. subsericea and 85% of water. Analysis of mean droplet diameter (155.2 ± 3.8 nm) confirmed this formulation as a nanoemulsion. It was able to induce mortality in D. peruvianus. It was observed no effect against acetylcholinesterase or mortality in mice induced by the formulation, suggesting the safety of this nanoemulsion for non-target organisms.ConclusionsThe present study suggests that the obtained O/A nanoemulsion may be useful to enhance water solubility of poor water soluble natural products with insecticidal activity, including the hexane-soluble fraction from ethanolic crude extract from fruits of Manilkara subsericea.
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.
The aim of this review is to explore the potentials existing in insecticides that are considered Insect Growth Regulators (IGR) for the control of insects considered crop pests, with an observation of the main mechanisms of neuroendocrine modifications, development and viability of the species used as study models. The data search on digital platforms, as well as the screening of materials about crop pests, resulted in 74 IGR references and their potentials. The analysis of the information found demonstrated a greater use in works of compounds belonging to chitin synthesis inhibitors class; and orders such as Hemiptera, Lepidoptera, Coleoptera, Orthoptera, Thysanoptera and Diptera were represented in the studies. The main types of activities reunited were morphological and anatomical modifications, reproductive modifications, alterations in developmental stage, alterations in developmental period, ovicidal activity, larvicidal/ninficidal activity and fagoinhibition. The congregated knowledge about the main pests used as study models, the main IGRs compounds and their biological potentials allow an evaluation of their use as an informative source for crop pest control methods.
Studies were carried out to evaluate the insecticidal activity of Pilocarpus spicatus Saint-Hilaire (Rutaceae) essential oil (EO) on the development of the Hemiptera Dysdercus peruvianus (Guérin-Méneville, 1831) and Oncopeltus fasciatus (Dallas, 1852). Gas Chromatography/Mass spectrometry analysis revealed a chemical composition with sabinene (32.27%) and sylvestrene (27.26%) as major constituents. Topical and continuous treatment with the pure EO induced 100% of mortality while serial dilutions of the EO induced different levels of lethality in a dose response manner. Median lethal dose (LD50) and lethal dose 90% (LD90) were determined. Malformations in insects and permanent or supernumerary nymphs were often observed after treatments, and the use of scanning electron microscopy allowed the analysis of morphological changes. The different biological effects of P. spicatus EO point out its potential as a rich source of bioactive molecules to be used as an alternative control method against agricultural pest insects.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.