Hormesis in the brown citrus aphid, Toxoptera citricida (Kirkaldy) (Hemiptera: Aphididae) exposed to sublethal doses of imidacloprid

Authors

  • Xue Dong Chen Entomology and Nematology Department, University of Florida, Citrus Research and Education Center, 700 Experiment station Rd, Lake Alfred, Florida 33850, USA
  • Meeja Seo Department of Agro-food Safety and Crop Protection, National Institute of Agricultural Science, RDA, 166 Nongsaengmyeong-ro, Wanju-gun, Republic of Korea
  • Timothy A Ebert Horticulture Department, University of Florida, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, Florida 33850, USA
  • Muhamad Ashfaq Department of Entomology, University of Agriculture Faisalabad, University Main Road, Faisalabad 38000, Pakistan
  • Wenquan Qin South China Agricultural University, Guangzhou 510642, China
  • Lukasz L Stelinski Entomology and Nematology Department, University of Florida, Citrus Research and Education Center, 700 Experiment station Rd, Lake Alfred, Florida 33850, USA

Abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a major pest that transmits phloem-limited, gram negative bacteria including ‘Candidatus’ liberibacter asiaticus (Clas), causing huanglongbing. Management of this pest relies primarily on insecticides, such as the neonicotinoid imidacloprid, that may affect secondary pests including the brown citrus aphid, Toxoptera citricida (Kirkaldy) (Hemiptera: Aphididae). Here, we report on direct toxicity and sublethal dose effects of imidacloprid on T. citricida nymphs and adults following direct contact and ingestion. We also examined transgenerational dose-response and hormetic effects following exposure of T. citricida to a sublethal concentration of imidacloprid. Toxicity of imidacloprid was similar for nymphs (0.6 ng per µL) and adults (1 ng per µL) at 72 h. Fecundity and finite rate of increase were greater for populations exposed to systemic and foliar treatments at a sublethal concentration (0.1 ng per µL) compared with untreated controls. Development times of first instar nymphs in the F1 generation and third instar nymphs in the F2 generation were significantly greater for individuals treated with the sublethal dose than an untreated control. Survival of second instar T. citricida on plants treated with a sublethal concentration also was significantly greater than controls. There also was a significant increase in fecundity of F1 and F2 individuals after sublethal treatment compared with controls. Our results indicated that a sublethal concentration of imidacloprid increased the reproductive performance and induced possible physiologically stimulative (hormetic) effects in T. citricida. Hormesis in secondary pests should be considered when developing a management program for pathogen vectors such as D. citri.

 

Resumen

El psílido asiático de los cítricos, Diaphorina citri Kuwayama (Hemiptera: Liviidae), es una plaga importante que transmite bacterias gramnegativas limitadas por el floema, incluyendo Liberibacter asiaticus (Clas), Candidatus, causando la enfermedad huanglongbing. El manejo de esta plaga se basa principalmente en insecticidas, como el imidacloprid neonicotinoide, que puede afectar a las plagas secundarias, incluido el pulgón marrón de los cítricos, Toxoptera citricida (Kirkaldy) (Hemiptera: Aphididae). Aquí, informamos sobre la toxicidad directa y los efectos de la dosis subletal de imidacloprid en ninfas de T. citricida y adultos después del contacto directo y la ingestión. También examinamos la respuesta a la dosis transgeneracional y los efectos horméticos después de la exposición de T. citricida a una concentración subletal de imidacloprid. La toxicidad de imidacloprid fue similar para las ninfas (0.6 ng por µL) y adultos (1 ng por µL) a las 72 h. La fecundidad y la tasa finita de aumento fueron mayores para las poblaciones expuestas a tratamientos sistémicos y foliares a una concentración subletal (0.1 ng por µL) en comparación con los controles no tratados. Los tiempos de desarrollo de las ninfas de primer estadio en la generación F1 y las ninfas del tercer estadio en la generación F2 fueron significativamente mayores para los individuos tratados con la dosis subletal que un control no tratado. La sobrevivencia del segundo estadio de T. citricida en plantas tratadas con una concentración subletal también fue significativamente mayor que los controles. También hubo un aumento significativo en la fecundidad de los individuos F1 y F2 después del tratamiento subletal en comparación con los controles. Nuestros resultados indicaron que una concentración subletal de imidacloprid aumentó el rendimiento reproductivo e indujo posibles efectos fisiológicamente estimulantes (horméticos) en T. citricida. Se debe considerar la hormesis en plagas secundarias al desarrollar un programa de manejo para vectores de patógenos como D. citri.

Key Words: secondary pests; stimulated reproduction; stress conditioning; toxicity; huanglongbing

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Published

2020-09-25

Issue

Vol. 103, No. 3 (September 2020)

Section

Research Papers

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