ARS | Publication request: Quarantine Strategies for Olive Fruit Fly (Diptera: Tephritidae): Low Temperature Storage, Brine, and Host Relations

Submitted to: Journal Of Economic Entomology
Publication Acceptance Date: May 17, 2004
Publication Date: August 1, 2004
Citation: Yokoyama, V.Y., Miller, G.T. 2004. Quarantine Strategies For Olive Fruit Fly (Diptera: Tephritidae): Low Temperature Storage, Brine, And Host Relations. Journal Of Economic Entomology. 97(4):1249-1253.

Interpretive Summary: Olive fruit fly has been recently introduced into California. The pest is a major threat to the U.S. olive industry and methods are needed to prevent its dispersal and future crop losses. Olives are preserved in brine solutions prior to canning and immersion of infested fruit in brine was found to prevent emergence of the larval stages of the pest. Low temperature storage of infested fruit was found to reduce pest numbers to very low levels, and fruit in bins attained lethal low temperatures after five days in cold storage. Preservation in brine and low temperature storage could be used to treat olives from orchards infested with olive fruit fly and minimize the chance of dispersal of the pest to processing plants. Laboratory tests showed a difference of susceptibility of olive fruit in different stages of maturity and by cultivar suggesting a need for orchard cultivation practices that would mitigate infestations and reduce the need for postharvest treatments. Research conclusions were submitted to the olive industry for immediate consideration as methods for mitigating olive fruit fly populations in California.

Technical Abstract: A dose-response relationship was not observed in olive fruit fly, Bactrocera oleae (Gmelin), larvae exposed to acetic acid concentrations (0-2.5%) used in commercial brine solutions to cure olives. Immersion in a 1% acetic acid brine solution impeded emergence of the immature stages. A 1 wk exposure of olives infested with olive fruit fly larvae to low temperature storage as a postharvest treatment at 0-1ºC resulted in 8% survival of the population, and exposures of 2 through 5 wk further reduced pupal and adult emergence to <1.0%. One to 2 wk exposures at 2-3ºC resulted in a significant decrease in survival from 20 to 3%, respectively, and longer durations of 3-5 wk reduced survival to <1.0%. Mean daily fruit pulp temperatures in olives in the top, middle, and bottom of plastic bins stored at 2-3ºC decreased by 5-8ºC from the first to the second day. Lowest temperatures were observed in the top and highest temperatures were observed in the middle layer of fruit which attained a mean temperature of 3.8ºC on day 5. Laboratory choice tests showed that olive fruit fly oviposited at a higher rate in late season Mission olives that were green than in fruit that were in the red blush maturity stage in tests with 1 and 3-4 d exposure periods, and an increase in duration of exposure was related to an increase in the total number of ovipositional sites. A higher percentage of olive fruit fly third instar, pupae, and adults were reared from green fruit than from fruit in the red blush stage after a 1 d exposure to oviposition. Manzanillo olives were more attractive for oviposition by olive fruit fly than Mission olives, and significantly more third instar, pupae, and adults developed in Manzanillo fruit that in Mission fruit in the red blush stage. These differences were related to the better quality and higher flesh content of the Manzanillo versus Mission olives used in the tests.