Olive Fruit Fly - Control Measures - Biotechnical Pest Management

Biotechnical Pest Management

Biotechnical pest management is currently mostly practiced on experimental or pilot farms or as an adjunct to the use of integrated pest traps, according to the function. It can be divided into two types:

• Monitoring traps (trap-tests) are used to detect the trends of the population of adults to estimate the threshold. Their density depends on the type and how the trap is used. The traps are strewn with a sticky entomological plastic substance.
• Traps for mass trapping (trap mass) are used to capture adults in mass to remove the population to levels that keep infestations below the threshold. Their density must be high (one trap per plant with a sexual attraction and/or food).

Mass trapping has so far given results comparable to those of the chemical pest management test implemented with the protein bait and only if implemented on a large scale. It therefore pays for pest management programs in the area, while not offering excellent results if done at enterprise level, especially on limited foundations. In the 1970s, not yet having discovered the fly pheromone, mass trapping tests were carried out using yellow traps, but this technique, requiring the placement of at least five traps per plant, was discarded as uneconomic, and had a strong negative impact on useful entomofauna.

Until the 1990s, the traps that have offered the best results were hand-crafted, made of wood soaked in a potent and long-lasting insecticide concentrate. Among the various insecticides, the best results are obtained with deltamethrin. These traps have been carried out, mass-trapping for over a decade with about 130,000 plants in Sardinia with results comparable to those obtained with the adulticide treatments using the protein bait. Since the late 1990s, traps are commercially available on an industrial scale (Ecotrap) for the mass trapping of the olive fruit fly. The Ecotrap is triggered by using a form of double attraction: the pheromone of the olive fruit fly and the ammonium bicarbonate, with biocidal action carried out by deltamethrin. Despite the limited series of tests carried out in recent years in some areas of the Mediterranean regions, the results are judged to be positive.

Three types of attractants are used in traps:

• Colour is used for its attractiveness in sticky traps. The adult olive fruit fly is attracted to the colour yellow. Since the yellow colour is not available, these traps can only be used for monitoring purposes.
• Pheromones, such as the synthetic pheromone 1,7-dioxaspire-5,5-undecane, is a reproduction of the main component of the natural sex pheromone emitted by the female to attract the male. Because of its selectivity, it is ideal for mass trapping, but the traps baited with the pheromone only show results that are not very effective: the pheromone of the olive fruit fly is in fact very volatile, and three to four weeks after the maximum capacity, is substantially less effective. Until the 1990s, the devices using gradual release of the pheromone proved unsuitable and it was necessary to replace them every 30–40 days.
• Food attractants are volatile nitrogenous substances that attract the flies to search for protein supplements to their diet. Protein hydrolysates and ammonium salts may be used as attractants. The disadvantage of these are that their function is affected by atmospheric conditions (temperature and relative humidity). The best results are achieved by combining a protein hydrolyzed with an ammonium salt in the same trap, or a combination of an attractive food with the pheromone.

Currently, sticky traps are the most reliable way of monitoring, as the thresholds calibrated with the traps have been extensively tested, whilst threshold assessments are still uncertain with chemiotropic traps. These are best suited, however, for mass trapping by combining two or three attractants, preferably one sexual and one food-based.