Description: “Bactrocera oleae”
Title: Bactrocera oleae
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Bactrocera oleae Gmelin
(Formerly in the genus Dacus)
Common name: Olive fruit fly (OFF).
Geographical distribution: Wherever olives are grown: the Mediterranean basin, northern, eastern and southern Africa, the Canary Islands, India, western Asia, Central America and California.
Host plants: Olea and its relatives.
Morphology: The white-yellowish, mature maggot is 6–7 mm long; females are about 5 mm in length, with transparent to brownish wings, with a spot on the tips. Both thorax and abdomen are mostly black, with yellow areas. The last abdominal segment is dark-yellow; the ovipositor is bright red.
Life history: The females lay their eggs into ripening fruit, in which the maggots feed and either pupate or drop to pupate in the soil. The optimum temperature is between 20-30ºC; under warmer conditions development is curtailed. The adults, which are mostly active during daytime, feed on honeydew, and on any available nitrogenous nutrients. They also puncture developing fruit to feed on the exudates and to gauge their suitability for oviposition. The females emit a relatively long-range sex pheromone. Under suitable conditions the OFF may complete 2-3 annual generations, each female producing several hundred eggs during several weeks. OFF populations usually have two annual peaks, in summer and in early autumn, as olive fruits ripen. On late ripening varieties the fly remains active till early winter.
Economic importance: A major pest of olive fruits that can destrot 100% of the crop. Direct damage is due to larval feeding within the fruit, which may drop or lose its commercial value, and to the female’s puncturing immature fruit (sterile punctures), that could cause its drop. Indirect injury from damaged olives is due to deterioration in the quality of the extracted oil, which turns acidic, and by the invasion of fungal pathogens through the puncture in the fruit. Unirrigated olive groves suffer less damage as compared to irrigated orchards, due to the smaller and later-maturing fruit.
Monitoring: The OFF is attracted to proteins and to the color yellow, and both are used for monitoring and deciding on the application of control measures. Various types of sticky traps, usually baited with protein hydrolysate and/or ammonium salts and an insecticide are used to determine the threshold for control treatments. Red sticky spheres are effective in capturing adult females. The weekly “catch” of 10 adults per trap in early summer, or 30 in autumn, is usually the trigger to initiate treatments. Another method is to collect several hundred fruits at random and determine their rate of infestation.
Control considerations: The economic impact of the pest varies with the intended use of the fruit. Olives intended for consumption (table olives) requires almost total control (e.g. zero larvae/fruit) and thus receive more attention and are sprayed more often. Fruit for oil pressing may have up to 10–30% infestation rates and still be acceptable. A major factor affecting management decisions is the effect of the alternation of olive fruit production, and the intensity of the attacks. OFF infestations are usually more intense in years of low production than in years of high production.
Plant resistance: Olive varieties differ in their suitability to the olive fly, the varieties Sevillano and Manzanillo being especially preferred. Spherical, large, and hard fruit seem to be preferred by the OFF over elongate, small, and soft fruit. However, complete or partial resistance has not yet been studied.
Mass trapping: Traps (such as the commercially produced Ecotrap® and Dacustrap®), containing an attractant (sometimes with a pesticide) were in wide use, but the realization that they also attract natural enemies of this and other pests reduced their application.
Sterile insect techniques (SIT) to control the olive fly are being developed in several Mediterranean countries. Another approach is causing incompatibility, in which the pest is infected by a Wolbachia strain, which results in embryonic mortality due to incompatible crosses.
Chemical control: Pesticides applied against OFF include avermectin, cyromazine, neem and spinosad(entry/Spinosades), but the pest is developing resistance to some of them. Kaolin clay, which forms a protective, repellent barrier film on the fruits provided good control in California, when applied every five to six weeks, starting as the fruit becomes vulnerable.
Biological control: Several hymenopteran parasitoids, like Psyttalia (Opius) concolor (Szepligeti), Pnigalio mediterraneus (Ferriére and Delucchi), Fopius arisanus (Sonan) and Diachasmimorpha krassi (Fullaway) parasitize about 25% of the pest populations. Nematodes were also successfully used against the pest in California.
Ant, T., Koukidou, M. (and 5 co-authors). 2011. Control of the olive fly using genetics-enhanced sterile insect technque. BMC Biology 10: 51.
Apostolaki, A., Livadaras, I. (and 4 co-authors). 2011. Transinfection of the olive fruit fly Bactrocera oleae with Wolbachia: towards a symbiont-based population control strategy. Journal of Applied Entomology 135: 546–553.
Argov, Y., Kuslitzky, W. and Hoelmer, K. 2012. Biological control of olive fruit fly, Bactrocera oleae, in Israel. IOBC/WPRS Bulletin 79: 79-85.
Burrack, H.J. and Zalom, F.G. 2008. Olive fruit fly (Diptera: Tephritidae) ovipositional preference and larval performance in several commercially important olive varieties in California. Journal of Economic Entomology 101: 750-758.
Daane, K.M. and Johnson, M.W. 2010. Olive fruit Fly: managing an ancient pest in modern tmes. Annual Review of Entomology 55: 151-169.
Daane, K.M., Johnson, M.W. (and 6 co-authors). 2011. Biological controls investigated to aid management of olive fruit fly in California. California Agriculture 65(1): 21-28.
El-Heneidy, A.H., Omar, A.H., El-Sherif, H. and El-Khawas, M. 2001. A survey and seasonal abundance of the parasitoids of the olive fruit fly Bacterocera (Dacus) oleae Gmel. (Diptera: Trypetidae) in Egypt. Arabian Journal of Plant Protection 19 : 80-85.
Haniotakis G.E., Kozyrakis, K. and Bonatsos, C. 1986. Control of the olive fruit fly, Dacus oleae Gmel. (Diptera, Tephritidae) by mass trapping: pilot scale feasibility study. Journal of Applied Entomology 101: 343-352.
Neuenschwander, P. 1982. Beneficial insects caught by yellow traps used in mass-trapping of the olive fruit fly, Dacus oleae. Entomologia Experimentalis et Applicata 32: 286–96.
Rizzo, R., Caleca, V. and Lombardo, A. 2012. Relation of fruit color, elongation, hardness, and volume to the infestation of olive cultivars by the olive fruit fly, Bactrocera oleae. Entomologia Experimentalis et Applicata 145: 15-22.
Sirjani, F.O., Lewis, E.E. and Kaya, H.K. 2009. Evaluation of entomopathogenic nematodes against the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae). Biological Control 48: 274-280.