Susceptibility of ‘Malama’ avocados to Bactrocera dorsalis (Diptera: Tephritidae) in Hawai'i and a proposed systems approach for market access

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

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2022
Publication Date: 10/22/2022
Citation: Follett, P.A., Asmus, G.M., Hamilton, L.J., Stockton, D.G. 2022. Susceptibility of ‘Malama’ avocados to Bactrocera dorsalis (Diptera: Tephritidae) in Hawai'i and a proposed systems approach for market access. Journal of Economic Entomology. 115(6):1894-1900. https://doi.org/10.1093/jee/toac150.
DOI: https://doi.org/10.1093/jee/toac150

Interpretive Summary: Hawaii grows several premium varieties of avocados. Currently, only the variety Sharwil can be exported to the continental United States by using a systems approach to minimize the risk of pest infestation. Research was conducted to determine if another variety, Malama, might also be suitable for export in a similar manner. Laboratory and field cage tests suggested Malama is a relatively poor host for the primary fruit fly quarantine pest Bactrocera dorsalis. Field sampling of fruit off the ground showed no infestation by B. dorsalis, suggesting Malama avocado is a poor host and that there is generally a low prevalence of B. dorsalis in avocado orchards. A systems approach is proposed to export Malama avocados from Hawaii to the U.S. mainland.

Technical Abstract: Avocados are generally poor hosts or nonhosts for tephritid fruit flies which can influence the type of mitigation measures that are required when developing export protocols for trade. We conducted experiments to determine the susceptibility of the avocado, Persea americana, cv. ‘Malama’ to infestation by oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) in Hawaii using laboratory and field no-choice cage testing and field sampling. In no-choice cage testing, infestation rate increased with decreasing fruit firmness over time after harvest. Although risk of infestation was negatively correlated with fruit firmness, about 50% of mature hard fruit exposed immediately after harvest became infested. In field cage tests, mature hard fruit on the tree at the 25% purple color stage were not infested, whereas fruit at the 50, 75 and 100 % purple color stages were infested at a relatively low rate. Field sampling of fallen ‘Malama’ fruit over two seasons showed no natural infestation by B. dorsalis and trap captures in avocado orchards averaged 0.13 + 0.03 (mean + SE) flies per trap per week, underscoring the poor host status of this cultivar and low prevalence of fruit flies. A systems approach based on poor host status, low prevalence and limited harvest period and distribution area is proposed.