Laboratory rearing and sex ratio of Apanteles opuntiarum (Hymenoptera: Braconidae), a potential biocontrol agent of Cactoblastis cactorum (Lepidoptera: Pyralidae)

Authors

  • Jessica Awad Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, Florida 32608, USA;
  • Amanda Hodges University of Florida, Department of Entomology and Nematology, Gainesville, Florida 32611, USA;
  • Stephen D Hight USDA, Agricultural Research Service, Tallahassee, Florida 32308, USA;
  • Mrittunjai Srivastava Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, Florida 32608, USA;
  • Amy C Howe Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, Florida 32608, USA;
  • Eric Rohrig Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, Florida 32608, USA;

Keywords:

local mate competition, inbreeding, Opuntia, invasive species

Abstract

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), is an invasive species in North America, where it poses a threat to species of Opuntia Mill. of economic and ecological importance. The parasitoid Apanteles opuntiarum Martinez & Berta (Hymenoptera: Braconidae) is currently under evaluation as a potential biological control agent. This study was conducted to develop a parasitoid rearing protocol, with special attention to laboratory sex ratio and the effects of inbreeding. The parasitoid rearing method used a natural cactus host diet for culture of the moths. Female wasps were mated with siblings, non-siblings, or a combination. Clutch size, clutch number, and offspring sex ratios were recorded. The effects of sibling mating on these factors were analyzed. Offspring of sibling-mated parasitoids exhibited a significant increase in female sex ratio. The rearing method produced 6 successive generations in captivity with no additional introductions of genetic material. Hence, the protocol appears suitable for long-term maintenance of quarantine colonies. The effects of inbreeding suggest that natural populations of A. opuntiarum are subject to local mate competition. Therefore, some amount of inbreeding is recommended for maintenance of an optimal sex ratio of A. opuntiarum in laboratory colonies.


 

Resumen

La polilla del cactus, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), es una especie invasora en América del Norte, donde representa una amenaza para las especies de importancia económica y ecológica de Opuntia Mill. El parasitoide Apanteles opuntiarum Martinez & Berta (Hymenoptera: Braconidae) está actualmente bajo evaluación como un agente potencial de control biológico. Este se realizó estudio para desarrollar un protocol de cria para el parasitoide, con atención especial a la proporción de hembras a machos en el laboratorio y los efectos de la endogamia. El método de crianza del parasitoide utiliza una dieta de cactus para criar las polillas. Las avispas hembras se aparearon con sus hermanos, con otros que no fueron hermanos o una combinación de los dos. Se registraron el tamaño del nido de huevos, el número de huevos en el nido y la proporción de hembras a machos de la descendencia. Se analizaron los efectos del apareamiento entre hermanos en estos factores. La descendencia de parasitoides apareados con sus hermanos mostró un aumento significativo en la proporción de hembras. El método de crianza produjo 6 generaciones sucesivas en cautiverio sin introducciones adicionales de material genético. Por lo tanto, el protocolo parece adecuado para el mantenimiento a largo plazo de las colonias de cuarentena. Los efectos de la endogamia sugieren que las poblaciones naturales de A. opuntiarum están sujetas a la competencia local de parejas. Por lo tanto, se recomienda cierta cantidad de endogamia para mantener una proporción de sexos óptima de A. opuntiarum en colonias de laboratorio.

 

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Published

2019-04-27

Issue

Vol 102, No. 1 (March 2019)

Section

Research Papers

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