Resident Hymenopteran Parasitoids with Potential Drosophilid Associations in Andean North Patagonia: Implications for the Biological Control of the Spotted Wing Drosophila.

The spotted wing drosophila, Drosophila suzukii Matsumura, is native to Southeast Asia and has become a serious pest of soft-skinned fruits worldwide. Several control methods are being tested worldwide as part of an integrated pest management approach. Biological control is a promising alternative tactic that can be used to manage D. suzukii populations, especially in unmanaged areas. This study aimed at exploring the diversity of resident hymenopteran parasitoids of drosophilids in northwestern Patagonia, where D. suzukii is considered an important pest. The survey also aimed to investigate possible associations between parasitoids and D. suzukii in several crops and non-crop fruits, and to determine D. suzukii fruits infestation levels. Fourteen sites with mainly berry crops were sampled biweekly using cider vinegar traps and collecting fresh fruits from a variety of crop and non-crop fruit plants. We identified five species of hymenopteran parasitoids, obtained from the baited traps, that have the potential to associate with D. suzukii: Leptopilina heterotoma Thomson, Ganaspis brasiliensis Ihering, Hexacola hexatoma Hartig (Figitidae), Pachycrepoideus vindemmiae Rondani (Pteromalidae), and Spalangia endius Walker (Spalangiidae). Leptopilina heterotoma is reported for the first time in Argentina. High numbers of D. suzukii adults were recovered from baited traps and field-collected fruits. However, no parasitoid emerged from D. suzukii pupae recovered from fruits, nor were any dead parasitoids recorded inside D. suzukii pupae. Overall infestation levels of D. suzukii on field-collected fruits did not differ significantly between species/varieties. The results are discussed with emphasis on the possible functionality and perspectives of using these species as biological control agents.

A Coordinated Sampling and Identification Methodology for Larval Parasitoids of Spotted-Wing Drosophila.

We provide recommendations for sampling and identification of introduced larval parasitoids of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). These parasitoids are either under consideration for importation (aka classical) biological control introductions, or their adventive (presumed to have been accidentally introduced) populations have recently been discovered in North America and Europe. Within the context of the ecology of D. suzukii and its parasitoids, we discuss advantages and disadvantages of estimating larval parasitism levels using different methods, including naturally collected fruit samples and sentinel baits. For most situations, we recommend repeated sampling of naturally occurring fruit rather than using sentinel baits to monitor seasonal dynamics of host plant-Drosophila-parasitoid associations. We describe how to separate Drosophilidae puparia from host fruit material in order to accurately estimate parasitism levels and establish host-parasitoid associations. We provide instructions for identification of emerging parasitoids and include a key to the common families of parasitoids of D. suzukii. We anticipate that the guidelines for methodology and interpretation of results that we provide here will form the basis for a large, multi-research team sampling effort in the coming years to characterize the biological control and nontarget impacts of accidentally and intentionally introduced larval parasitoids of D. suzukii in several regions of the world.

Best Timing to Determine Field Parasitism by Released Diachasmimorpha longicaudata (Hymenoptera: Braconidae) Against Anastrepha (Diptera: Tephritidae) Pest Populations.

Our objective was to determine the timing of the highest parasitic activity by released Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) in areas with fruits of sour orange and hog plums infested by Anastrepha ludens (Loew) and Anastrepha obliqua (McQuart) (Diptera: Tephritidae), under shaded and sunny conditions. Percent parasitism along fruit sampling period was related to host availability, which was influenced by the fruit size rather than environmental conditions. The highest parasitism in sour orange was obtained just the first day after release, but in hog plums this was observed during the first 3 days without significant differences between them. The levels of fruit infestation and parasitism were higher in shaded trees in sour orange as in hog plums. The high availability of larvae and the small size of hog plums were decisive for obtaining high levels of parasitism and keeping parasitoids near the release points. By contrast, the size and thick rind of sour orange provided to the larvae a physical refuge that was associated with lower parasitism, causing that parasitoids spread out in search of hosts more accessible. In sour orange, parasitism was exclusively by D. longicaudata, while in hog plums, we additionally found the coexistence of four native parasitoid species. This information suggests that in sour orange, the sampling should be performed 1 day after release, while in hog plums, the samplings can be extended to within the first 3 days. Such sampling can serve to better estimate the effect of D. longicaudata releases against Anastrepha pest populations in different fruit types.