Due to the concern for the environment and human health, agriculture is increasingly focusing on the development of new methods of plant protection, which could decrease or replace the use of synthetic insecticides. The accelerated transition is also encouraged by the observed resistance of several harmful insects to chemical substances; e.g. the resistance of the red flour beetle (Tribolium castaneum Herbst) to the widespread fumigant phosphine. Essential oils are mixtures of biologically active chemical compounds, consisting of 20-60 components, of which 2-3 main components represent a majority and the remaining components are present in traces. They are known for their high volatility, since they can transition into gaseous state already at room temperature or at a slightly higher temperature, and are most suitable for use in the form of a fumigants, but are also quite successful in the form of repellents and as contact substances. In addition to insects, they effectively suppress bacteria, fungi, viruses and nematodes, but the use of individual types of essential oils differs in regard of the type of the pest. They do not represent danger for people, animals and fish, since they are not toxic for these groups or are toxic for them in a significantly lower extent, because of their high volatility it would be even harder for these groups to get in contact with them. All of the 4 presented essential oils, Sweet orange (Citrus x sinensis (L.) Osbeck); species Citrus), Basil (Ocimum basilicum L.), Rosemary (Rosmarinus officinalis L.) and Garlic (Allium sativum L.) show high fumigant activity against the warehouse pests such as maize weevil (Sitphilus zeamays Motschulsky), red flour beetle (Tribolium castaneum Herbst) and lesser grain borer (Rhyzopertha dominica Fabricius), while the successfulness of Rosemary was also observed in the group of phosphine resistant adult specimens of the red flour beetle. The essential oil of garlic and its main component dialyl trisulfide were with their application on grain samples successful in the complete discontinuance of further reproduction of the red flour beetle, without simultaneously causing poorer corn grain sprouting ability.
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