Chemical ecology of the Mediterranean fruit fly Ceratitis capitata (Wied.) : interaction of pheromone with host plant volatiles

Bakri, Abdeljelil (1990) Chemical ecology of the Mediterranean fruit fly Ceratitis capitata (Wied.) : interaction of pheromone with host plant volatiles. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Citrus peel and leaf volatiles enhanced the attraction of females to the pheromone produced by live males when bioassayed in an olfactometer with four choices. The effect of combining the odours was synergistic and greater with peel volatiles. In still air bioassays, changes in responsiveness of flies in relation to progressive changes in the odour and colour of the oranges was investigated. As fruits matured, more flies were attracted to them. However, fermenting fruits were the most attractive to both males and females. Orange volatiles were analyzed by gas chromatography, and certain characteristic major monoterpenes such as limonene, linalool and α-terpineol were tested against the flies. In still air bioassays, limonene, linalool and α-terpineol induced aggregation behaviour in males and pseudomale behaviour in virgin females. The median efficient dose (ED₅₀) of limonene, attracting 50% of the population of males tested, decreased as the time of exposure to limonene increased. After two minutes, the ED₅₀ was 286 and at twenty minutes it was 24.9. In a wind tunnel bioassay, males were exposed to trimedlure, limonene and α-terpineol. These three chemicals elicited up-wind flights involving various anemotactic behaviour. Aggregation occurred on the floor of a cage beneath a suspended chemical source. The attraction of males to limonene assessed in a wind tunnel was optimal at mid-day i.e. six hours after the beginning of the photophase. The percentage of flies flying up-wind and landing was highest within the first ten minutes of the sixty-minute bioassay. The influence of the presence of orange volatiles on the catches of traps baited with various pheromone component blends was investigated a) in the presence of two trees in a closed room inside the laboratory and b) in the field in Morocco. Male catches with trimedlure baited traps were not affected by orange volatiles. However, female catches with certain synthetic pheromone-baited traps increased in the absence of oranges. Blends such as : ethyl acetate, geranyl acetate, linalool; linalool, pyrroline and a mixture of five acetates were the most promising. The colour of the trap also enhanced pheromone performance. A synthetic pheromone blend was more attractive to flies when yellow traps were used instead of orange traps in simulated field conditions.

This record has no associated files available for download.