Abstract
The association between the use of synthetic insecticides and the appearance of resistant insects, human poisoning and the environment contamination generated the need to develop new forms to pest control, and essential oils stand out as an alternative. However, due to their volatility and instability, their use in native form is unfeasible. It is possible to circumvent these problems by their encapsulation, and the use of polymeric nanoparticles for this purpose has many advantages, since these systems prevent the oil degradation, and control its release. The first in vivo trials of chitosan nanoparticles containing essential oils with insecticidal activity were published in the late 2010s. Considering the growing interest in this subject, as can be seen from the increase in the number of publications, this review aimed to gather all the papers that presented biological assays using essential oils encapsulated in chitosan nanoparticles against insects. Further, the techniques used to prepare these nanoparticles are also discussed. It was possible to note that the technique called complex coacervation led to smaller particles and most articles describing in vivo tests of chitosan nanoparticles containing essential oils assess their larvicidal activity. Among the tested nanoparticles, the one that had the best larvicidal activity in acute toxicity tests were those obtained by complexing of chitosan with cashew gum and those with the best residual activity were the cross-linked with glutaraldehyde. Chitosan nanoparticles containing essential oils also increased their insecticidal activity in toxicity tests against adult beetles.
Highlights
Insects are a class of highly specialized animals (Engel, 2015) and most of them are beneficial to mankind, whether by participating in pollination of plants, providing products of commercial interest, such as silk and honey or by their participation in the environmental balance (You et al, 2005; Rader et al, 2016)
These results indicate a great need for the development of new strategies to combat insects that act as pests, and several researches have been developed with the aim of finding substitutes for synthetic insecticides, such as the application of suppression and replacement of the insect population (Leftwich et al, 2016) or the use of biopesticides, e.g. products of microbiological origin and botanical insecticides (Glare et al, 2012; Miresmailli e Isman, 2014)
They observed that, in the time interval analyzed, the L. sidoides essential oil encapsulated inside the nanoparticles maintains the larvicide effect and reaches mortality rates from 52% to 92% and comments that this result is compatible with that obtained with pure oil, the authors do not show any result with the oil alone, so that one can’t verify which increase in the half-life of the oil in solution is obtained with the nanoparticles
Summary
Insects are a class of highly specialized animals (Engel, 2015) and most of them are beneficial to mankind, whether by participating in pollination of plants, providing products of commercial interest, such as silk and honey or by their participation in the environmental balance (You et al, 2005; Rader et al, 2016). The use of these pesticides is associated with several problems, including the selection of pesticide resistant insects (Sparks et al, 2019), making it difficult to control vectors of pathogenic organisms and leading to the emergence or re-emergence of mosquito-borne diseases (Dahmana, Mediannikov, 2020); effects on nontarget species, negatively affecting parameters such as survival, reproduction and growth (Gustone et al, 2021); and cases of humans’ intoxication, for example, it is estimated that poisoning by organophosphate insecticides causes two million hospitalizations per year (Eddleston, 2020) These results indicate a great need for the development of new strategies to combat insects that act as pests, and several researches have been developed with the aim of finding substitutes for synthetic insecticides, such as the application of suppression and replacement of the insect population (Leftwich et al, 2016) or the use of biopesticides, e.g. products of microbiological origin and botanical insecticides (Glare et al, 2012; Miresmailli e Isman, 2014). The discussion of the results extracted from the selected articles was preceded by a brief comment on essential oils and chitosan
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