Addition of cinnamon oil improves toxicity of rotenone to Spodoptera litura (Lepidoptera: Noctuidae) larvae

  • Zihao Li Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou, China
  • Rilin Huang Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou, China
  • Weisheng Li Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou, China
  • Dongmei Cheng Department of Plant Protection, Zhongkai University of Agriculture and Engineering, Guangzhou, China
  • Runqian Mao Guangdong Entomological Institute/Guangdong Provincial Public Laboratory on Wild Animal Conservation and Management, Guangzhou, China
  • Zhixiang Zhang Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou, China State Key Laboratory for Conservation and Utilization of SuBtropical Agro-Bioresources, Guangzhou, China
Keywords: midgut penetration, botanical insecticide, synergism, paraffin section

Abstract

Abstract

Although rotenone is widely used as a pesticide, it has a low level of insecticidal activity on Spodoptera litura (F.) (Lepidoptera: Noctuidae). To gain a better understanding of the high tolerance to rotenone, a synergist (cinnamon oil) was added, and the comparative physiological impacts were assessed. After rotenone treatment, a considerable amount of rotenone was discharged in excreta, but extremely low levels were found in the ventral nerve cord and brain. By contrast, the rotenone + cinnamon oil treatment group showed an increased amount of rotenone in the ventral nerve cord and brain. The co-toxicity coefficient for rotenone + cinnamon was 213, indicating synergism. The midgut cells from insects treated with rotenone alone, and the controls, exhibited no significant differences, whereas those of the rotenone + cinnamon oil group had larger intercellular spaces. These findings suggest that rotenone alone could not effectively penetrate the midgut, perhaps accounting for its low toxicity to S. litura. The rotenone + cinnamon oil mixture apparently affected midgut cell spacing and membrane permeability, thus effectively increasing rotenone toxicity.

 

Resumen

Aunque la rotenona es ampliamente utilizada como pesticida, tiene un bajo nivel de actividad insecticida sobre Spodoptera litura (F.) (Lepidoptera: Noctuidae). Para obtener una mejor comprensión de la alta tolerancia a la rotenona, se añadió un sinergista (aceite de canela) y se evaluaron los impactos fisiológicos comparativos. Después del tratamiento con rotenona, se descargó una cantidad considerable de rotenona en el excremento, pero se encontraron niveles extremadamente bajos en el cordón nervioso ventral y en el cerebro. Por el contrario, el grupo de tratamiento con aceite de rotenona + canela mostró una mayor cantidad de rotenona en el cordón nervioso ventral y en el cerebro. El coeficiente de co-toxicidad para rotenona + canela fue de 213, lo que indica sinergismo. Las células del intestino medio de los insectos tratados con la rotenona sola, y los controles, no mostraron diferencias significativas, mientras que las del grupo de rotenona + aceite de canela tenían mayores espacios intercelulares. Estos hallazgos sugieren que la rotenona por sí sola no podría penetrar eficazmente en el intestino medio, tal vez debido a su baja toxicidad para S. litura. La mezcla de rotenona + aceite de canela aparentemente afectó el espaciamiento de las células del intestino medio y la permeabilidad de la membrana, aumentando así efectivamente la toxicidad de la rotenona.

 

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Published
2017-10-10
Section
Research Papers