Periods of infestation assessment of Bactrocera oleae (Rossi)

The olive fruit fly is a major pest of olives worldwide. Females lay the eggs inside the fruits and larvae live as fruit miners within the mesocarp, consuming the olive pulp and mining thin, sigmoid sub- epidermic tunnels which become progressively larger and deeper as their growth progress proceeds. Potential losses caused include consumption of fruit pulp by larvae, pre-harvest fruit drop, and reduction of olive oil quality caused by the presence of microorganisms such as bacteria, yeasts, and molds. In the case of table olives, the attacked fruits are totally lost as they are considered unsuitable for marketing. Under an organic farming or integrated pest management point of view farmers should use pesticides and other forms of direct intervention only when they are economically and ecologically justified, ensuring the plant protection and reducing or minimizing the risk to human health and the environment.

In this sense, the monitoring and infestation assessment are essential to determine the need (or not) of intervention. Visual observation of fruits should be done from BBCH 75 phenological scale (fruits about 50% of final size, stone becomes lignified, showing cutting resistance) onwards and at a weekly periodicity and supported by adequate monitoring of adults in pheromone traps (see practice abstract entitled “The use of sex pheromone traps for olive fruit fly, Bactrocera oleae (Rossi), monitoring”). Under a stereoscopic microscope, fruits should be dissected and inspected for the presence of alive forms (eggs, larvae, pupae). The reference values for economic thresholds levels differ between countries, and farmers should follow guidelines of their country agriculture services.