The olive moth develops three generations per year, each one synchronized with a specific olive tree organ. The phyllophagous generation, develops between November and April, and larvae feeds on leaves and buds. During spring, females lay eggs on flower buds initiating the anthophagous generation, which held from April to June, and whose larvae consume the flower buds and flowers. The symptoms of this generation are easily identified by the existence of silky yarns involving the inflorescences, in which excrement and brownish petals accumulate. Later, the females emerge and lay eggs on the small fruits, mainly in the calyx, initiating the carpophagous generation; the larvae of this generation bore into the olive stone and consume the tissue inside; after completing the development, these larvae leave the fruits to pupate on branches fissures, causing an important fruit dropping.
Anthophagous and carpophagous generations can be responsible for great economic losses, being essential to perform an adequate risk assessment of the pest. In the anthophagous generation, observation should be done from BBCH 57 phenological scale (corolla green-coloured and longer than calyx). For the carpophagous generation, observation should be done from BBCH 71 phenological scale (fruits about 10% of final size). However, the determination of the periods to assess infestation should be supported by an adequate adult monitoring in pheromone traps (see practice abstract entitled “The use of sex pheromone traps for olive moth, Prays oleae (Bernard), monitoring”). The reference values for economic thresholds levels differ between countries and farmers should follow guidelines of their country agriculture services.