Tolerances of apple maggot (Diptera: Tephritidae) larvae and different age puparia to water flotation and immersion

Authors: Yee, Wee

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2021
Publication Date: 10/6/2021
Citation: Yee, W.L. 2021. Tolerances of apple maggot (Diptera: Tephritidae) larvae and different age puparia to water flotation and immersion. Environmental Entomology. 50(6):1407-1415. https://doi.org/10.1093/ee/nvab102.
DOI: https://doi.org/10.1093/ee/nvab102

Interpretive Summary: In the Pacific Northwest of the USA, apple maggot fly is a quarantine pest of apple. Immature stages of the fly may tolerate immersion in water and could potentially be dispersed in waterways to new habitats. However, whether immatures can survive in water and for how long to make this a possibility is unknown. Personnel at the USDA laboratory in Wapato, WA, determined survival of apple maggot larvae and pupae after water immersion for 2-12 days in the laboratory. It was found that larvae and newly-formed pupae were susceptible to water while older pupae were more tolerant and survived in water as long as controls. Results are important in that they suggest older apple maggot pupae can be dispersed in waterways to establish in new habitats, such as currently fly-free areas

Technical Abstract: Tolerance of terrestrial insects in temperate regions to water immersion and hypoxia has rarely been studied but can be an important adaptation to wet environments, with implications for insect dispersal through waterways. In the Pacific Northwest of the U.S., apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), can be found in riparian habitats that may become flooded. Here, survival of R. pomonella larvae and different age puparia after flotation or immersion in 13.3°C or 21.1°C water for 1–12 d was determined. Larvae sank in water and when submerged for 1 or 2 d suffered greater mortality than controls, with all larvae dying after 2 d in 21.1°C water. Fewer 1–2 d old puparia floated in water than 13–15 d old puparia. When immersed in water with 5.5–7 ppm oxygen (hypoxic conditions) for 1–12 d, the younger puparia suffered greater mortality than older puparia, which were not affected by water immersion. Correspondingly, fewer adult flies eclosed from puparia that had been water treated at 1–2 than 13–15 d old. Adult flies from 13–15 d old pre-chill and from 198–144 d old post-chill puparia that had been water treated eclosed later than control flies, but treatment flies survived 47–65 d and reproduced. Although newly-formed puparia are susceptible to hypoxic water conditions, increased buoyancy and water tolerance occur rapidly after formation, perhaps making possible survival and dispersal of older puparia in waterways to establish in new habitats