Chemical composition, acaricidal and insecticidal effects of essential oil fromAchillea filipendulinaagainst two arthropod pests;Oryzaephilus surinamensisandTetranychus urticae

Exploration of Synergistic Pesticidal Activities, Control Effects and Toxicology Study of a Monoterpene Essential Oil with Two Natural Alkaloids

With the increasing development of pest resistances, it is not easy to achieve satisfactory control effects by using only one agrochemical. Additionally, although the alkaloid matrine (MT) isolated from Sophora flavescens is now utilized as a botanical pesticide in China, in fact, its pesticidal activities are much lower in magnitude than those of commercially agrochemicals. To improve its pesticidal activities, here, the joint pesticidal effects of MT with another alkaloid oxymatrine (OMT) (isolated from S. flavescens) and the monoterpene essential oil 1,8-cineole (CN) (isolated from the eucalyptus leaves) were investigated in the laboratory and greenhouse conditions. Moreover, their toxicological properties were also studied. Against Plutella xylostella, when the mass ratio of MT and OMT was 8/2, good larvicidal activity was obtained; against Tetranychus urticae, when the mass ratio of MT and OMT was 3/7, good acaricidal activity was obtained. Especially when MT and OMT were combined with CN, the significant synergistic effects were observed: against P. xylostella, the co-toxicity coefficient (CTC) of MT/OMT (8/2)/CN was 213; against T. urticae, the CTC of MT/OMT (3/7)/CN was 252. Moreover, the activity changes over time of two detoxification enzymes, carboxylesterase (CarE) and glutathione S-transferase (GST) of P. xylostella treated with MT/OMT (8/2)/CN, were observed. In addition, by scanning electron microscope (SEM), the toxicological study suggested that the acaricidal activity of MT/OMT (3/7)/CN may be related to the damage of the cuticle layer crest of T. urticae.

Chemical profile, characterization and acaricidal activity of essential oils of three plant species and their nanoemulsions against Tyrophagus putrescentiae, a stored-food mite

Essential oils of Ocimum basilicum (L.), Achillea fragrantissima (Forssk.) and Achillea santolina (L.) were obtained by hydrodistillation and analyzed using gas chromatography (GC) and GC/mass spectrometry (MS). Oil-in-water nanoemulsions (10% active ingredient) were prepared through a high-energy (ultrasonication) emulsification process. Nanoemulsions were characterized by viscosity, pH, thermodynamic stability, droplet size, polydispersity index (PDI) and scanning electron microscopy (SEM) measurements. The plant oils and their nanoemulsions showed considerable acaricidal activity against the mold mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae). In a contact toxicity bioassay and 48 h post treatment, O. basilicum oil was the most toxic, followed by A. fragrantissima and A. santolina, where LC₅₀ values were 8.4, 14.1 and 21.8 µl/cm², respectively. LC₅₀ for benzyl benzoate, a standard acaricide was 9.8 µl/cm². Upon fumigation, responses also varied according to the test oil. Based on the 48-h LC₅₀ values, the same manner of activity was also observed, where O. basilicum was the most toxic followed by A. fragrantissima and A. santolina. When prepared as nanoemulsions (particle size from 78.5 to 104.6) and tested as fumigants, toxicity of the oils was increased drastically with LC₅₀ values of 2.2, 4.7, and 9.6 µl/l air for O. basilicum, A. fragrantissima and A. santolina, respectively. The oils showed a moderate to strong residual acaricidal activity, where O. basilicum oil was the most effective. The results suggest that appropriate nanoemulsions containing the tested oils can be developed to control T. putrescentiae after the required toxicological assessments.

Artemisia magellanica. Chemical Composition of the Essential Oil from an Unexplored Endemic Species of Patagonia

The essential oil composition of the aerial parts of Artemisia magellanica Sch. Bip. (Asteraceae), native to Patagonia, was analyzed by GC-FID-MS. This is the first report on the essential oil composition of A. magellanica. A total of 113 components were identified accounting for 95.6-95.7 % of the oil. The essential oil was characterized by a high percentage of γ-costol (21.0-43.5 %), selina-4,11-diene, (Z)-β-ocimene, (E)-β-farnesene, (Z)-en-yn-dicycloether and 23 different esters (28.7 %). In turn, Artemisia biennis, a species native to North America, which is considered by some authors to be conspecific with A. magellanica, yielded an essential oil that was rich in (Z)-β-ocimene (34.7 %), (E)-β-farnesene (40.0 %) and the acetylenes (Z)- and (E)-en-yn-dicycloethers (11.0 %). Thus, as A. biennis lacks the three main components present in A. magellanica, namely γ-costol, 2-methylbutyl 2-methylbutyrate and selina-4,11-diene, these compounds could be considered as potential chemical markers for A. magellanica since they are absent or only found as minor constituents in other members of the genus. The data presented herein is also useful for genus taxonomy.