Poor host status of Australian finger lime, Citrus australasica, to Ceratitis capitata, Zeugodacus cucurbitae, and Bactrocera dorsalis (Diptera: Tephritidae) in Hawai’i

Authors: Follett, Peter; Asmus, Glenn; Hamilton, Lindsey

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2022
Publication Date: 2/8/2022
Publication URL: https://handle.nal.usda.gov/10113/7683928
Citation: Follett, P.A., Asmus, G.M., Hamilton, L.J. 2022. Poor host status of Australian finger lime, Citrus australasica, to Ceratitis capitata, Zeugodacus cucurbitae, and Bactrocera dorsalis (Diptera: Tephritidae) in Hawai’i. Insects. 13(2). Article 177. https://doi.org/10.3390/insects13020177.
DOI: https://doi.org/10.3390/insects13020177

Interpretive Summary: Tephritid fruit flies are major economic pests for fruit production and impede international trade. Different host fruits are known to vary in their suitability for fruit flies to complete their life cycle. International regulatory standards that define the legal host status for tephritid fruit flies categorize fruits as a natural host, a conditional host, or a nonhost. For those fruits that are natural or conditional hosts, infestation rate can vary as a spectrum ranging from highly attractive fruits supporting large numbers of fruit flies to very poor hosts supporting low numbers. Finger lime, Citrus australasica, is a new crop in Hawai’i and no information existed on its susceptibility to Hawai’i’s tephritid fruit fly pests. Host status testing was conducted using no-choice cage tests and field collections. Ceratitis capitata and Zeugodacus cucurbitae readily oviposited into finger limes but individuals rarely developed to the pupal or adult stage, showing strong host plant resistance. Finger limes was not infested by Bactrocera dorsalis and is probably a nonhost. Heat treatment and irradiation are approved postharvest treatments for exporting Hawai’ian Citrus sp. to the continental U.S. Due to its poor host status, finger lime may also be amenable to a systems approach for export.

Technical Abstract: We examined the host status of the Australian finger lime, Citrus australiasica [F. Muell.] Swingle (Rutaceae) to Hawai’i’s tephritid fruit fly pests using laboratory and field studies. In high density (500 flies, males and females) no-choice cage exposures, both undamaged and punctured finger limes were infested by Ceratitis capitata and Zeugodacus cucurbitae at a low rate compared to papaya controls, whereas Bactrocera dorsalis did not infest undamaged fruit indicating finger lime is a nonhost. In low density (50 females) no-choice cage exposures, C. capitata and Z. cucurbitae readily oviposited in undamaged fruit but individuals rarely developed to the pupal or adult stage. For C. ceratitis, 274 finger limes exposed to 2,000 gravid females, which laid an estimated 14,384 eggs, produced 2 pupae and no adults. For Z. cucurbitae, 299 fruit exposed to 2,000 gravid females, which laid an estimated 4,484 eggs, produced 4 pupae and 1 adult. Field collections from the tree and off the ground from commercial farms produced five C. capitata pupa and one adult from 1,119 fruit and an infestation rate of 0.05 flies per kilogram of fruit; field sampling found no Z. cucurbitae or B. dorsalis infestation but the number of fruit available was too low to demonstrate nonhost status with a high degree of confidence.