Abstract
The olive fruit fly, Bactrocera oleae, is considered the main olive pest worldwide, and has been the target of biological control programmes through the release of the braconid parasitoid Psyttalia concolor. Laboratory tests were performed to evaluate the influence of distance from the host on parasitisation, placing larvae of the substitute host Ceratitis capitata at seven distances (0, 0.5, 1, 1.5, 2, 2.5, 3 mm) and four different time periods (7, 15, 30, 60 min). Moreover, field collected olives of Ogliarola Barese cultivar infested by B. oleae were exposed to P. concolor females to confirm its ability to parasitise B. oleae in small olives. Psyttalia concolor oviposition was inhibited at 2.5 and 3 mm due to the ovipositor length of the parasitoid females (2.7 mm). Hosts were easily parasitised at distances between 0 and 1.5 mm. The thin fruit pulp (up to 3.5 mm) of field collected olives allowed the parasitisation to occur also in mature fruits. At the best combination distance/time (0 mm, 30 min), tests performed with different larvae/parasitoid female ratio showed an increasing emergence of P. concolor (from 20% to 57%) with larvae/parasitoid ratio increasing from 0.11 to 0.74. The results of the present study might optimise the mass rearing of P. concolor, through a proper setting of its parameters, such as the host/parasitoid ratio, exposure distances, and interaction time.
Highlights
Olive cultivation is of remarkable economic importance in the Mediterranean area
To assess differences in the ovipositor length of P. concolor reared on C. capitata and P. concolor obtained from B. oleae, 23 females of P. concolor reared in the laboratory on C. capitata, and 47 females obtained from B. oleae, 23 females of P. concolor reared in the laboratory on C. capitata, and 47 females that emerged from B. oleae puparia obtained from cultivated olives (25 specimens) and Mediterranean that emerged from B. oleae puparia obtained from cultivated olives (25 specimens) and Mediterranean wild olives (22) collected in 2010–2011 in Sicily (Trapani province) were dissected to extract the wild olives (22) collected in 2010–2011 in Sicily (Trapani province) were dissected to extract the ovipositor from the gaster
Significant differences in the terebra length were found between the P. concolor females emerged from the laboratory host C. capitata (2.71 mm) and from the natural host B. oleae collected in Mediterranean wild olive (2.49 mm, Figure 3)
Summary
Olive cultivation is of remarkable economic importance in the Mediterranean area. Yield losses for harvested fruits due to the olive fruit fly were estimated to be at least 15% of the total olive production [1].The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is commonly considered the key pest of olive fruits in the Mediterranean climatic conditions, and the tolerable limit of B. oleae exit holes to obtain high quality oil has been recently assessed [2].The common technique for pest control is the application of broad-spectrum insecticides on the whole canopy or spraying with poisoned-protein baits on part of the tree canopy. Yield losses for harvested fruits due to the olive fruit fly were estimated to be at least 15% of the total olive production [1]. The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is commonly considered the key pest of olive fruits in the Mediterranean climatic conditions, and the tolerable limit of B. oleae exit holes to obtain high quality oil has been recently assessed [2]. Integrated pest management is considered the best strategy for sustainable crop protection. This includes the use of less susceptible plant varieties, cultural techniques, the use of natural enemies, microbial pesticides (entomopathogenic bacteria, viruses, and fungi), natural plant insecticides, semiochemicals, and insect growth regulators
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