Essential oils (EOs) and individual compounds act as fumigants against insects found in stored products. In fumigant assays, Sitophilus zeamais Motschulsky adults were treated with essential oils derived from Aphyllocladus decussatus Hieron, Aloysia polystachya Griseb, Minthostachys verticillata Griseb Epling and Tagetes minuta L , which are rich in ketones and their major components: α-thujone, R-carvone, S-carvone, (-) menthone, R (+) pulegone and E-Z-ocimenone. M. verticillata oil was the most toxic ( LC 50 : 116.6 µl /L air) characterized by a high percentage of menthone (40.1%) and pulegone (43.7%). All ketones showed insecticidal activity against S. zeamais. However, pulegone (LC 50 : 11.8 µl/L air), R-carvone (LC 50 : 17.5 µl/L air), S-carvone (LC 50 : 28.1 µl/L air) and E-Z-ocimenone (LC 50 : 42.3 µl/L air) were the most toxic. These ketones are α,b-unsaturated carbonyl. This feature could play a fundamental role in the increase of insecticidal activity against S. zeamais.

In Argentina, oregano (Origanum spp.) is one of the most important aromatic species. Leaves and flowering tops are used as seasoning, targeting the retail consumer, industrial and less to export. Local production has low-average yields due to the variability of cultivated material, the vegetative propagation methods used, and the lack of knowledge and adaptive experimentation on advanced cultivation practices. Clones of oregano grown in the country were collected in order to characterize the germplasm used in Argentina. Twelve oregano clones, sanitized by meristems culture and micropropagated in vitro, were field evaluated in three different growing locations. Regardless of growing site, the quantitative variables with more discriminating value were essential oils yield, internode length, length of the longest branch, fresh weight, dry weight of leaf and stem, leaf/stem ratio, and leaf area. Based on the quantitative traits, oregano clones can be classified into four groups. From the observations based on botanical characteristics, it was determined that the evaluated clones belong to three different taxa: Origanum vulgare ssp. vulgare, Origanum vulgare ssp. hirtum, and Origanum x majoricum (hybrid). Within each group, the clones belong to the same taxon.

Essential oils composition of three Tagetes minuta varieties and a wild population (WP) from Argentina and their in vitro and in vivo nematicidal activity against root-knot nematode, Meloidogyne javanica, are described. All T. minuta EOs tested were very active against nematode juveniles (J2), but the strongest nematicidal effects were exhibited by the TmV3 variety oil, characterized by a high content of (E)-ocimenone. High nematode egg hatching suppression (> 90%) was induced by TmV3 EO after five days of incubation. In vivo tests on tomato seedlings showed a significant reduction of infection rate of M. javanica J2 treated with TmV3 and WP oils at sub lethal dose. Therefore, EOs from chemically stable new varieties of T. minuta could be environmentally friendly nematicidal agents.

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