Previously introduced braconid parasitoids target recent olive fruit fly (Bactrocera oleae) invaders in Hawai’i

Authors: Stockton, Dara; Aldebron, Charlotte; GUTIERREZ-COARITE, ROSEMARY - University Of Hawaii; Manoukis, Nicholas

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2023
Publication Date: 12/18/2023
Citation: Stockton, D.G., Aldebron, C., Gutierrez-Coarite, R., Manoukis, N. 2023. Previously introduced braconid parasitoids target recent olive fruit fly (Bactrocera oleae) invaders in Hawai’i . Scientific Reports. 13. Article 22559. https://doi.org/10.1038/s41598-023-49999-x.
DOI: https://doi.org/10.1038/s41598-023-49999-x

Interpretive Summary: Fruit fly incursions to and from Hawaii are a threat to food security in the United States. In 2019 a new invasive fruit fly species arrived in Hawaii, the olive fruit fly, and has since begun affecting Hawaii's burgeoning olive industry. Our study aimed to investigate potential biological control agents in Hawaii for use in future management programs. We collected olive samples during the 2021 and 2022 production season, and in the lab at USDA PBARC in Hilo, HI reared out any olive fruit fly or parasitoids present. We found two small parasitoid wasp species in our samples, and report that both likely came from prior releases of these wasps to control other fruit flies in Hawaii. We also found some differences in abundance of the wasps at different locations around Hawaii suggesting that one parasitoid may be better suited to some climates in the islands than others, or perhaps is more prevalent in those environments naturally. We make suggestions for future research and recommend augmentative releases of Fopius arisanus to help combat olive fruit fly.

Technical Abstract: In the latest of five tephritid species of economic importance established in Hawai’i, the olive fruit fly Bactrocera oleae (Diptera: Tephritidae) was detected on Maui and Hawai’i Islands in 2019, affecting yields and quality of the state’s emerging olive oil industry. Given previous parasitoid releases to control other invasive frugivorous tephritids in Hawai’i, we were interested in determining whether 1) these parasitoids were found targeting olive fly in field, 2) whether cultivar differences affected parasitization, and 3) if there was a seasonal pattern of parasitization that could inform future management decisions. To address these questions, we collected data from 2 olive growing sites on the big island of Hawai’i as well as 2 sites on Maui during 2021. During 2022, we added an additional site on Hawai’i Island where we discovered B. oleae infested feral olives. During the fruiting season we collected monthly samples and reared out B. oleae in the lab. We detected two previously introduced braconid wasps: first Diachasmimorpha tryoni during 2021 and 2022 and later Fopius arisanus during the 2022 collection. Cultivar effects were limited to a single site in our study, where more D. tryoni were reared from ‘Arbequina’ olives. Seasonality of olive fruit fly and parasitoid activity was earlier in lower elevation sites, as expected based on tree phenology and temperature-dependent insect development. This represents the first report of D. tryoni parasitism activity against B. oleae and may reflect elevational effects combined with the ecological complexity in interactions between multiple invasive arthropod pests, their invasive and cultivated plant hosts, and introduced braconid parasitoids.