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

Authors: AWAD, JESSICA - FLORIDA DEPARTMENT OF AGRICULTURE AND CONSUMER SERVICES; HODGES, AMANDA - UNIVERSITY OF FLORIDA; HIGHT, STEPHEN; SRIVASTAVA, MRITTUNJAI - FLORIDA DEPARTMENT OF AGRICULTURE AND CONSUMER SERVICES; HOWE, AMY - FLORIDA DEPARTMENT OF AGRICULTURE AND CONSUMER SERVICES; ROHIG, ERIC - FLORIDA DEPARTMENT OF AGRICULTURE AND CONSUMER SERVICES

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2018
Publication Date: 4/11/2019
Citation: Awad, J., Hodges, A., Hight, S.D., Srivastava, M., Howe, A., Rohig, E. 2019. Laboratory rearing and sex ratio of Apanteles opuntiarum (Hymenoptera: Braconidae), a potential biocontrol agent of Cactoblastis cactorum (Lepidoptera: Pyralidae). Florida Entomologist. 102(1):216-221. https://doi.org/10.1653/024.102.0135.
DOI: https://doi.org/10.1653/024.102.0135

Interpretive Summary: The Argentine cactus moth is an invasive pest spreading across the southern USA destroying prickly pear cactus. A parasitic wasp was brought from Argentina to a Florida quarantine for testing as a potential biological control agent against. The wasp is host specific in Argentina, meaning that it attacks only the target caterpillar and no other cactus feeding Argentine caterpillars. Before the wasp can be introduced into the USA environment, it must be shown to not attack native USA cactus feeding caterpillars. Scientists with USDA Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology, Tallahassee, Florida, and collaborators at the Florida Department of Agriculture and Consumer Services, Division of Plant Industry developed a reliable rearing method of the wasp so that host specificity tests could be conducted in the Florida quarantine. A laboratory rearing protocol was successful in producing multiple generations of parasitoids, with sufficient numbers of female offspring to maintain the colony and conduct host range testing. Studies are proceeding in the quarantine to determine if the wasp is safe for release into the natural USA environment as a major, environmental safe agent for control of the Argentine cactus moth.

Technical 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 six 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.