Scale insects mortality in olive trees in Rio Grande do Sul (Brasil)

Abstract: The olive crop as a business is a recent activity in Rio Grande do Sul (Brazil), and there are few studies related to insects associated with this crop. This study aimed at identifying the species of scale insects present in olive trees (Olea europaea L.) and to evaluate and quantify their natural mortality. The research was conducted in an olive orchard, Arbequina variety, six years old, located in Caçapava do Sul (30°33’29.79″S and 53º24’09.48″W), RS, Brazil. The grove with 475 plants per hectare was cultivated under traditional management. From April 2012 to March 2013, monthly, 20 trees were sampled randomly and, from each quadrant of their canopies (northern, southern, eastern and western), two branches were randomly taken, one from inside and the other from outside the canopy, each of 20 to 30 cm long with at least 20 leaves. Scale insects were counted and identified as living, dead and with evidence of parasitism. The scale insects assemblage found comprised of a single species of Coccidae, Saissetia oleae, and five Diaspididae, Aonidiella aurantii, Hemiberlesia cyanophylli, Acutaspis paulista, Aspidiotus nerii and Melanaspis obscura; S. oleae being the most abundant scale species. For all species, the parasitism was not the main mortality factor. For S. oleae the highest mortality may be associated with intraspecific competition. The total parasitism rate was 3.86%. Saissetia oleae had the lowest rate, while A. nerii and M. obscura had the highest parasitism registered among all the species.