Does the Neotropical-native parasitoid Ganaspis pelleranoi successfully attack the worldwide invasive pest Drosophila suzukii?

The Asian Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a harmful invasive pest widespread throughout Argentinian fruit-producing regions. It coexists with both pests, the sub-Saharan African Ceratitis capitata (Wiedemann) and the Neotropical-native Anastrepha fraterculus (Wiedemann) (both Diptera: Tephritidae), in northwestern Argentina. The Neotropical-native parasitoid Ganaspis pelleranoi (Brèthes) (Hymenoptera: Figitidae) is frequently found in non-crop fruit infested by those frugivorous dipterans. The northwestern Argentinian region is known for producing and exporting berries and citrus, which are affected by those pests. Thus, eco-friendly control strategies are under assessment. This study mainly assessed the potential of the G. pelleranoi population lineage from Tucumán (Gp_Tuc) as a D. suzukii biocontrol agent. First, both the host-killing effectiveness and the reproductive success of Gp_Tuc on larvae of D. suzukii, C. capitata, A. fraterculus, and Drosophila melanogaster Meigen were compared in no-choice tests under laboratory conditions. Then, the Gp_Tuc host preference was evaluated in dual-choice tests (D. suzukii vs. C. capitata or A. fraterculus) under laboratory and field conditions. Naive parasitoid females were allowed to forage for 8 h on screen-covered Petri dishes filled with host larvae under laboratory conditions and for 48 h on peaches inoculated with host larvae under field conditions. Host puparia dissections were performed to determine the number and condition of parasitoid eggs, first and second instars, such as alive/dead, without/with melanization process, and proportions of parasitized, superparasitized, and dead puparia. Drosophila suzukii was not a suitable host for the successful development of Gp_Tuc immature stages as they did not overcome the host's immune system. However, Gp_Tuc performed efficiently regarding D. suzukii mortality, but parasitoid specificity was restricted to both tephritid species as only thriving offspring were achieved from them. Interestingly, the effectiveness of Gp_Tuc on D. suzukii increased when it co-occurred with C. capitata instead of A. fraterculus, the preferred host.