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BACKGROUND The application of film seed coating with some plant extracts against stored insect pests was an alternative approach for insect protection instead of using chemical insecticides. The overuse of insecticides has contributed to both human health and environmental problems. The hexane extracts of Illicium verum (HS) and Syzygium aromaticum (HC) were evaluated against bruchid beetles (Callosobruchus maculatus and Callosobruchus chinensis). The insecticidal activities and enhancing seed germination after being coated by various concentrations of extracts, purified fraction (PF) of extracts, standard chemicals of PF, fipronil insecticide (FI), and coating agent groups were evaluated after stored. RESULTS Both HS and HC at 3% concentrations were more effective against C. maculatus than C. chinensis with LT50 values of 1.60–1.90 and 3.44–3.62 h, respectively. They could also kill those insects with a higher number than that of standards. The HS and HC could inhibit the progeny population of those insects over 95.6% with no significant difference compared to the FI group. The eugenol standard was the most effective and completely inhibited the emergence compared with trans‐anethol standard and PFs. The seed that was coated with 1% of HS and stored at 4 °C for 6 months showed no effect on seed germination with no significant difference between FI and control groups. CONCLUSION The application of 1% of HS incorporated in the film seed coating against bruchid beetles and did not affect seed germination quality after 6 months. © 2021 Society of Chemical Industry

The African red mite (Eutetranychus africanus [Tucker]) is an important pest species of some economic plants.The objective of the present study was to evaluate the effectiveness of nanoemulsions consisting of citronella grass, lemongrass, clove, and cinnamon essential oils and their main chemical compounds against the African red mite; their toxicity, egg-laying inhibition, and repellent effect on the mite were determined. Essential oil nanoemulsions (nEOs) were prepared by mixing the essential oils with different surfactants and co-surfactants. Approximately 10 to 15 female mites were transferred to treated leaves placed on soaked cotton and kept in a Petri dish. Mite mortality and number of eggs laid were checked after 24 h. As for the repellency test, the selected test consisted of dipping a half leaf into the nEOs, while the other half leaf was dipped in a control (water). The repellency rate was evaluated after 24 h. Results revealed that citronella grass nEOs exhibited a highly toxic effect on the mite and only a 0.6% concentration caused 100% mite mortality. Geraniol, one of the main chemical compounds of citronella grass, represented the highest egg-laying inhibition at a 0.2% concentration with a mean of 0.1 egg compared with 4.7 eggs in the control. Furthermore, nEOs from citronella grass at a 0.1% concentration were extremely repellent against the mite with 95% repellency after 24 h. Therefore, the citronella grass essential oil nanoemulsion is appropriate for use to effectively control the African red mite.

Essential oils obtained from three medicinal plant species, namely, cinnamon (Cinnamomum bejolghota [Buch.-Ham.] Sweet), citronella grass (Cymbopogon nardus Rendle), and clove (Syzygium aromaticum [L.] Merr. & L. M. Perry), were sprayed on allergenic materials (house dust plus spent mite medium produced by the European house dust mite, Dermatophagoides pteronyssinus [Trouessart]) to evaluate the effects of the oils on allergen levels. A 1% solution of each essential oil in 95% ethanol was sprayed on the allergenic materials (which contained about 50 µg of allergen per gram of material), and 95% ethanol, water, and untreated allergenic materials were used as controls. The sprayed materials were allowed to stand for 48 h, and then allergen levels were analyzed by means of an enzyme-linked immunosorbent assay method. The results showed that the essential oil from C. bejolghota reduced the amount of allergen 99.4%, and the essential oils from C. nardus and S. aromaticum reduced the amounts by 77.1% and 74.0%, respectively. In contrast, the 95% ethanol control reduced the amount of allergen by only 9.8%.

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