Eucalyptus essential oils in pest control: a review of chemical composition and applications against insects and mites

The genus Eucalyptus (Myrtaceae) is native from Australia and includes about 900 species. Eucalyptus plantations are nowadays extended worldwide, particularly in the tropical and temperate regions. Plants, giving large biomasses rich in essential oils (EOs), are a great source of bioactive natural compounds that can be used in sectors other than medical. EOs can act as insecticides and acaricides, and represent valuable alternatives to the synthetic pest controllers, being biodegradable and human-environmental safe products. Botanical insecticides/ acaricides can be applied as a strategy in pests management programs, and laboratory investigations represent an important preliminary step that provide an understanding of insect/mite-plant interactions. In this review, 117 articles were analysed regarding 71 Eucalyptus species and 5 hybrids, among which E. globulus and E. camaldulensis result the most investigated species. The major constituents of most Eucalyptus EOs are monoterpenes and sesquiterpenes including 1.8-cineole, alpha-pinene, p-cymene, alpha-terpineol, limonene, gamma-terpinene, alpha-phellandrene, beta-pinene, globulol, aromadendrene, beta-phellandrene. The EOs reviewed were tested on 50 insects and 13 mites species. Aedes aegypti, Musca domestica, Tribolium castaneum, Callosobruchus maculatus, Sitophilus oryzae, Pediculus humanus are the most studied target species. Several developmental stages of the tested animal have been investigated: eggs, larvae, pupae/nymphae and adults. Several parameters have been monitored using different methods to study the repellent, insecticidal and acaricidal activities. Contact and topical toxicity, fumigant toxicity, fecundity, ovicidal, repellent, antifeedant activities, acetylcholinesterase inhibition and antennal response have been evaluated. Results were expressed as lethal concentrations/doses, lethal times, percentages, etc. Furthermore, the phytochemical profiles of the Eucalyptus species EOs analysed, and the spectrum of insects and mites on which the Eucalyptus EOs have been tested as repellent, insecticidal and acaricidal were summarized, to promote their applications in the areas of food storage, plant protection and human/animal health.