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The secret chemical arsenal of plants in the fight against rodents

Some Mediterranean plants that are found in nature, in green spaces or even on our balcony, offer much more than a good aesthetic result. They hide within them, through their biology, a natural arsenal of chemical warfare. This arsenal constitutes the natural defense of plants, otherwise known as inductive defense, against a multitude of enemies. These substances, found in the leaves, roots or other parts of plants, can also act as natural repellants or even as poison against animal enemies that are a nuisance to plants and humans.

There are many examples. Essential oils extracted from bergamot (Citrus bergamia), which contain components such as limonene, linalool and linalyl acetate, have a rodent-repellent effect either alone or in combination with essential oils from thyme (Thymus vulgaris) and lavender (Lavandula angustifolia). In addition, essential oils extracted from peppermint (Mentha piperita L.) in combination with essential oils from gaultheria (Gaultheria procumbens) and bergamot (Citrus bergamia), prevent rodents from approaching the application sites. Similar results have been observed with extracts from Alexandrian clover (Trifolium alexandrium), which can be sprayed on food and other materials that we want to protect.

However, there are even more drastic substances. For example, chives (Urginea martima), contain the toxic substance scilliroside which exhibits rodenticidal properties in the form of an extract or powder from the bulb of the plant. Nerium oleander contains the toxic substances oleandrin and nerine, which are cardiac glycosides (organic compounds that help the heart function properly). The consumption of leaves of the plant causes damage to vital organs of rodents, while their extract has adverse effects on hematological and histopathological parameters. Finally, wild calendula (Calendula aegyptiaka) flower extract contains amounts of cardiac glycosides flavonoids, saponins, tannins and triterpenes, which can be lethal to rodents.

Mediterranean plants and their repellent and toxic properties against rodents were the subject of the research entitled “A review of endemic plant species of Greece for managing rodent damages in agriculture” presented as part of the MED4PEST research project by researchers of the Hellenic Mediterranean University at the Conference “RETASTE: Rethink Food Resources, Losses and Waste” in Athens on September 27-29, 2023. The MED4PEST project aims to reduce the economic damage caused by rodents to the outdoor and greenhouse crops of the Mediterranean and of course Greece. Reducing the loss caused by rodents has physical and economic benefits, in addition to the ecological objective of the project.

MED4PEST is funded by the PRIMA foundation and is a collaboration of 6 partners: the Hellenic Mediterranean University (HMU) form Greece, the Mohammed V University of Rabat (MVUR) from Morocco, the National Institute for Agricultural Research of Rabat (INRA) also from Morocco, the CYENS Center of Excellence (CYENS) from Cyprus, as well as two branches of the social enterprise MetaMeta, one based in the Netherlands (Meta-Meta Research – MMR) and one based in Turkey (Meta-Meta Anatolia – MMA). The lead partner of MED4PEST is Meta-Meta Anatolia (MMA).

Greece is represented in the project by the Department of Agriculture of the Hellenic Mediterranean University, with Prof. Dr. Thrasyvoulos Manios and Asst. Prof. Dr. Ioannis Daliakopoulos and scientific collaborators Ioannis Marakis, Agronomist MSc and Ioannis Louloudakis, Technologist Agronomist MSc. According to the Greek researchers, “the results of this research will be used to develop alternative methods of repelling rodents in order to reduce as much as possible the use of chemical rodenticides that burden the environment as well as non-target animals such as predators”.

The PRIMA Program (Partnership for Research and Innovation in the Mediterranean Area) is a European Union funding body with the main objective of developing research and innovation capacities and devising innovative solutions for addressing critical problems in the areas of water management and agri-food systems in the Mediterranean.

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