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<p>Fungi of the genus <i>Metarhizium</i> and their associated volatile organic compounds (VOCs) are natural allies, offering promising new alternatives for agricultural pest management. This study investigates the susceptibility and response of <i>Tetranychus urticae</i> Koch (Acari: Tetranychidae) to <i>Metarhizium anisopliae</i> AUMC 3262 and <i>Metarhizium brunneum</i> ARSEF 4556, and their associated VOCs. <i>M. brunneum</i> ARSEF 4556 displayed greater effectiveness and a lower median lethal time (LT<sub>50</sub>) than <i>M. anisopliae</i>&#xa0;AUMC 3262 against <i>T. urticae</i> adult females. Conidial concentrations of 1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ conidia&#xa0;ml<sup>-1</sup> resulted in mortality percentages of 56.00 ± 3.71%, 65.00 ± 4.28%, and 78.00 ± 4.89% for <i>M. anisopliae</i> AUMC 3262, and 68.00 ± 2.00%, 79.00 ± 5.25%, and 88.00 ± 2.49% for <i>M. brunneum</i> ARSEF 4556, five days post-treatment. The dual&#xa0;choice assay indicated that dry conidia of <i>M. brunneum</i> ARSEF 4556 and&#xa0;<i>M. anisopliae</i> AUMC 3262 exhibited high repellent properties toward <i>T. urticae</i> adult females. The repellent properties of isoamyl alcohol, a common volatile produced by&#xa0;<i>M. brunneum</i>&#xa0;ARSEF 4556 and&#xa0;<i>M. anisopliae</i>&#xa0;AUMC 3262, were subsequently assessed and compared to the promising ketone 3-octanone. The findings indicated that adult female&#xa0;<i>T. urticae</i>&#xa0;were repelled by isoamyl alcohol in a concentration-dependent manner, regardless of the exposure time. In contrast, the repellent activity of 3-octanone was not affected by either concentration or time. However, it is worth noting that 3-octanone has higher acaricidal activity than isoamyl alcohol, with lower median lethal concentration (LC<sub>50</sub>) and lethal time (LT<sub>50</sub>) values. This study concluded that <i>T. urticae</i> could interact with <i>M. brunneum</i>&#xa0;ARSEF 4556 and <i>M. anisopliae</i> AUMC 3262, resulting in either direct mortality by fungal conidia or repulsion by VOCs emitted by them. The study also suggested that fungal volatiles, such as isoamyl alcohol and 3-octanone, could be developed as promising semiochemicals in <i>T. urticae</i> management programs.</p>

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Metarhizium species and their volatile organic compounds: promising alternatives for the two-spotted spider mite, Tetranychus urticae management

  • 期刊论文

  • 发表日期：

    2025年4月17日

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  • Rana H. M. Hussien,
  • Shimaa Ghareeb,
  • Fatma Sh. Kalmosh

摘要

Fungi of the genus Metarhizium and their associated volatile organic compounds (VOCs) are natural allies, offering promising new alternatives for agricultural pest management. This study investigates the susceptibility and response of Tetranychus urticae Koch (Acari: Tetranychidae) to Metarhizium anisopliae AUMC 3262 and Metarhizium brunneum ARSEF 4556, and their associated VOCs. M. brunneum ARSEF 4556 displayed greater effectiveness and a lower median lethal time (LT50) than M. anisopliae AUMC 3262 against T. urticae adult females. Conidial concentrations of 1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ conidia ml-1 resulted in mortality percentages of 56.00 ± 3.71%, 65.00 ± 4.28%, and 78.00 ± 4.89% for M. anisopliae AUMC 3262, and 68.00 ± 2.00%, 79.00 ± 5.25%, and 88.00 ± 2.49% for M. brunneum ARSEF 4556, five days post-treatment. The dual choice assay indicated that dry conidia of M. brunneum ARSEF 4556 and M. anisopliae AUMC 3262 exhibited high repellent properties toward T. urticae adult females. The repellent properties of isoamyl alcohol, a common volatile produced by M. brunneum ARSEF 4556 and M. anisopliae AUMC 3262, were subsequently assessed and compared to the promising ketone 3-octanone. The findings indicated that adult female T. urticae were repelled by isoamyl alcohol in a concentration-dependent manner, regardless of the exposure time. In contrast, the repellent activity of 3-octanone was not affected by either concentration or time. However, it is worth noting that 3-octanone has higher acaricidal activity than isoamyl alcohol, with lower median lethal concentration (LC50) and lethal time (LT50) values. This study concluded that T. urticae could interact with M. brunneum ARSEF 4556 and M. anisopliae AUMC 3262, resulting in either direct mortality by fungal conidia or repulsion by VOCs emitted by them. The study also suggested that fungal volatiles, such as isoamyl alcohol and 3-octanone, could be developed as promising semiochemicals in T. urticae management programs.