Journal of Insect Science (2007) 7 (16), 9-10

K.A. Hoelmer, A.A. Kirk and C.H. Pickett (2007)
Ecology of the olive fruit fly and its parasitoids in wild olives in Southern Africa
Journal of Insect Science 7 (16), 9-10
XIV International Entomophagous Insects Workshop - Jun. 11-15, 2006, Newark, Delaware, U.S.A.
Abstract: The olive fruit fly, Bactrocera oleae (Rossi) (Diptera; Tephritidae) is a key pest of cultivated olives throughout the Mediterranean region, where it has no effective natural enemies. Olive flies are specific to Olea europaea, of which various subspecies occur widely in parts of Africa, southern Europe and Asia as far east as China. Field surveys conducted in the 20th century documented a diverse assemblage of natural enemies on cultivated and wild olives in southern and eastern Africa, but previous attempts to introduce these species into Europe were not successful. The recent establishment of B. oleae in California has renewed interest in classical biological control of this pest. To identify and obtain new natural enemies of olive fly for evaluation and potential establishment in California, we surveyed wild olives, Olea europaea subsp. cuspidata, in several regions of South Africa (RSA) and Namibia during 2001-2005. Wild olives have a wide distribution across southern Africa, but rainfall patterns strongly influence the seasonal occurrence and abundance of fruit, and consequently the abundance of flies and their parasitoids. The annual pattern of rainfall in South Africa varies among regions, leading to a wide range in flowering and fruiting phenology. Olives tend to set fruit more frequently and produce more numerous and larger fruits in the moister regions of West Cape Province, RSA, than in drier regions. Olive fly populations were consistently highest in West Cape Province, as were populations of their natural enemies. Drier regions support populations of olive fly at much lower levels. In drier habitats the fruit is less likely to ripen. Fruit size and pulp thickness also influences fly infestation rates. Wild olive fruits possess relatively thin pulp (ca. 1-3 mm), offering little food for fly larvae. Pulp thickness is relevant for biological control, because cultivated olives have much thicker pulp in which fly larvae may be able to escape the reach of parasitoids equipped with relatively short ovipositors. Several braconid species in the genera Bracon, Psyttalia and Utetes were the most abundant fly parasitoids reared from infested olive fruit collected in southern Africa. The dominant species varied from region to region and from one year to the next. Braconid parasitoids were often present even at low densities of olive fly. The parasitoid fauna of southern Africa was similar to that found in Kenya but much richer than the diversity known from North Africa.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Kim A. Hoelmer, Alan A. Kirk, Charles H. Pickett

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
environment - cropping system/rotation
Research topic(s) for beneficials or antagonists:
surveys/distribution/isolation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Bactrocera oleae		Kenya
	Bactrocera oleae		Namibia
	Bactrocera oleae		South Africa