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    Item type:Publication,
    Synergistic Larvicidal and Pupicidal Effects of Monoterpene Mixtures Against Aedes aegypti with Low Toxicity to Guppies and Honeybees
    (2025-07-01)
    Sittichok, Sirawut
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    Passara, Hataichanok
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    Moungthipmalai, Tanapoom
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    Sinthusiri, Jirisuda
    ;
    Murata, Kouhei
    The present study evaluated the larvicidal and pupicidal activities of pure and mixed monoterpene formulations—eucalyptol, geranial, trans-anethole, and trans-cinnamaldehyde—against Aedes aegypti and compared them with 1% (w/w) temephos. Safety bioassays of all formulations on non-target species confirmed their safety. The combined mixture of eucalyptol + trans-anethole at 400 µg/mL exhibited stronger larvicidal activity, with an LC<inf>50</inf> of 176 µg/mL, while the combination of trans-anethole + geranial at 400 µg/mL exhibited stronger pupicidal activity with an LC<inf>50</inf> of 167 µg/mL. Both formulations were more effective than a 1% temephos. All the mixture formulations were more strongly synergistic compared to pure formulations, with an increased mortality value (IMV) of 25% to 95%. External morphological aberrations observed at death included swelling of the respiratory system. Importantly, all the formulations were safe for two non-target species: guppies (Poecilia reticulata) and honeybees (Apis mellifera). The combination formulations are strong larvicides and pupicides for controlling Ae. Aegypti, which will help reduce the spread of viruses carried by this vector.
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    Item type:Publication,
    Synergistic Larvicidal and Pupicidal Toxicity and the Morphological Impact of the Dengue Vector (Aedes aegypti) Induced by Geranial and trans-Cinnamaldehyde
    (2024-09-01)
    Sittichok, Sirawut
    ;
    Passara, Hataichanok
    ;
    Sinthusiri, Jirisuda
    ;
    Moungthipmalai, Tanapoom
    ;
    Puwanard, Cheepchanok
    Monoterpenes are effective and eco-friendly alternatives to conventional chemical larvicides. We tested single and binary mixtures of monoterpenes—geranial and trans-cinnamaldehyde—for their larvicidal and pupicidal activities against Aedes aegypti L. and for non-target toxicity on guppies (Poecilia reticulata Peters), using 1% (w/w) temephos as a reference. Geranial and trans-cinnamaldehyde at 250 ppm showed stronger larvicidal and pupicidal activities with a 100% mortality rate and an LT<inf>50</inf> ranging from 0.3 to 0.6 h. All combinations were strongly synergistic against larvae and pupae compared to single formulations, with an increased mortality value (IMV) of 6% to 93%. The combination of geranial + trans-cinnamaldehyde (1:1) at 200 ppm showed the highest impact, with an IMV of 93%. The strongest larvicidal and pupicidal activities, a 100% mortality rate, and an LT<inf>50</inf> of 0.2 h were achieved by geranial + trans-cinnamaldehyde (1:1) 500 ppm. They were thirty times more effective than a 1% temephos solution (LT<inf>50</inf> ranging from 6.7 to 96 h) and caused obviously shriveled cuticles and a swollen respiratory system. All single and binary mixtures were not toxic to the guppies. Thus, the combination of geranial + trans-cinnamaldehyde has great potential as a safe insecticide for controlling mosquito larvae and pupae.
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    Item type:Publication,
    Combinations of plant essential oils and their major compositions inducing mortality and morphological abnormality of Aedes aegypti and Aedes albopictus
    (2022-05-01)
    Soonwera, Mayura
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    Moungthipmalai, Tanapoom
    ;
    Aungtikun, Jirapon
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    Sittichok, Sirawut
    Extensive uses of synthetic insecticides to control mosquito's populations have induced the insects to develop resistance against them, rendering them ineffective today. Moreover, they cause serious impacts on human health and the ecosystem. Therefore, safe and effective natural alternatives are needed. This study evaluated the larvicidal and pupicidal activities of essential oils (EOs) from Illicium verum and Zanthoxylum limonella and the major constituents against Aedes aegypti and Aedes albopictus mosquitoes as well as recorded their morphological aberrations at death. The GC-MS analysis showed that trans-anethole was the major constituent of I. verum EO, and limonene was the major constituent of Z. limonella EO. Both were more effective against the larvae and pupae of Ae. aegypti than those of Ae. albopictus. A 2.5% I. verum EO + 2.5% trans-anethole combination showed the highest larvicidal and pupicidal effects against Ae. aegypti and Ae. albopictus with an LT<inf>50</inf> ranging from 0.2-6.9 h. Between the two tested constituents, trans-anethole exhibited stronger larvicidal and pupicidal activities (LC<inf>50</inf> ranging 2.4–3.4%) against the two tested mosquito species than d-limonene (LC<inf>50</inf> ranging 2.5–3.7%). Most importantly, 5% trans-anethole, 5% d-limonene, and 2.5% I. verum EO + 2.5% trans-anethole were more effective (LT<inf>50</inf> ranging 0.1–0.3 h) than 1% (w/w) temephos (LT<inf>50</inf> ranging 2.9–3.1 h). Morphological aberrations at death observed were such as color pigment and thorax shape abnormalities. To conclude, trans-anethole, d-limonene, and a combination of I. verum EO + trans-anethole, are natural compounds that not only are as effective as temephos at the time of this study, but should be also be much safer to human health.