Soglie di dannosità e strategie di controllo di Bactrocera oleae (Rossi) nell'olivicoltura biologica da tavola

Abstract

Olive fly control is the main limit to the diffusion of organic table olives production, because of the lack of effective larvicides. Few studies on damages in table olives due to B. oleae and on applied damage thresholds are recorded. Results of this research show that sterile and fertile olive fly punctures are no more detectable by the naked eye on the surface of processed table olives; on the contrary exit holes are still clearly visible and affect the appearance of olives. Damage threshold applied before sizing and selection by processors of Nocellara del Belice cultivar ignores punctures and consists of 10% of 3rd instar larvae or 5% of exit holes; after sizing and selection exit holes threshold lowers to 1%. Our tests on olive fly control in organic table olive production suggest that early ripening cultivars, less susceptible cultivars, an orchard management able to reach olive size early, a low olive fly pressure (because of the year or local conditions) allow to maintain table olives below the damage threshold; one to three sprays with clays and copper products, particularly kaolin and copper hydroxide, in most cases resulted in an effective reduction of B. oleae attacks.