Augmentative releases of Aphytis melinus (Hymenoptera: Aphelinidae) to control Aonidiella aurantii (Homoptera: Diaspididae) in a Sicilian citrus grove

Releases of Aphytis melinus DeBach were conducted to control the populations of the California red scale, Aonidiella aurantii (Maskell) in an orange orchard in Eastern Sicily. The trial was performed in 2004-2006 on 1-ha plots (3 replicates) releasing 120,000 adults/ha compared with untreated control. The releases started immediately after the first male captures on pheromone traps and were repeated on a biweekly basis releasing each time around 20% of the yearly per-hectare total on ten release points per plot. To monitor the effect of wasp releases on scale densities, in coincidence with peak male flight activity based on trap catches and at fruit harvest, twigs (40cm 1-2 years old from each cardinal direction between 1.5 and 2m above the ground on 2 trees per plot) and fruits (1 fruit from each cardinal direction on 24 trees per plot) were sampled, observed under the binocular scope and all the California red scale stages recorded and identified as alive, dead and parasitized (by ecto- or endo-parasitoids). The results showed, at fruit harvest in 2006, a significant difference in the percentage of fruits having one or more second-instar or older California red scale between the released field and the untreated control. Thus periodical releases of A. melinus appear to be a viable option for scale control in an integrated pest management system.