Pests that affect the olive groves on Terceira island, Azores


Abstract: The olive tree is cultivated in the Azores Archipelago only on two islands: Terceiraand Pico. In Terceira Island, the area is about 60 hectares and it is confined to the Porto Martinsarea, in the southeast of Terceira Island. All the production is for table olives.The main phytosanitary problems identified damaging the olive trees are: olive fruit fly(Bactrocera oleae Gmelin.), olive moth (Prays oleae Bern.), black scale (Saissetia oleae Oliv.)and now the new pest that has emerged in this area at the beginning of June 2008, the olive psylla(Euphyllura olivina Costa).The field methodology used for monitoring and making the risk estimate for these pests was asfollows: for the olive moth, one Delta trap with a specific sexual pheromone to capture adults andone yellow chromotropic trap also with a specific sexual pheromone in each one of the five oliveorchards selected to be studied. During all the survey period, these five olive orchards werevisited every fifteen days. For the fruit damage evaluation caused by the olive fly, 250 fruits werecollected from 5 trees (50 fruits in each tree) and for the evaluation of the area affected by olivepsylla, 3 inflorescences or branches with leaves were analyzed in each of the 826 trees inside ofthe production area within a range of 500 meters from the detected infestation focus. All thecollected data were then analyzed in Excel and from there exported to ArcGIS 9.1, which enabledthe development of olive psylla GIS distribution maps from all the olive production area.The results allow us to conclude that the olive fruit fly is the main pest of this culture, having ithighest population abundance in June, August and October, with October the month with thehighest captures. The olive moth reaches high population densities in July. Beyond that, it waspossible to get some better knowledge about the olive psylla infestation focus, where it registeredtwo generations (one at the beginnings of June and the other at the endings of October) and thegeographic distribution all over the production area, based on the GIS maps analysis.From the olive fly fruit damage analysis there was an average of 83% infestation over the fivesurveyed orchards. In some orchards, where there was no treatment, the infestation reached the98%, meaning that all production was lost.

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