Population fluctuation and infestation levels of Zaprionus indianus Gupta (Diptera: Drosophilidae) in berry crops of northwestern Argentina

The African fig fly (Zaprionus indianus Gupta; Diptera: Drosophilidae) was recently reported infesting fruit in commercial raspberry (Rubus idaeus L.) orchards of northwestern Argentina (an important berry exporting region), representing a latent threat to farmers and the regional economy. The objective of this work was to determine Z. indianus population fluctuation and fruit infestation by this fly during the 2020-2021 harvest season in berry crops of Tucumán, northwestern Argentina. For the first objective, a trapping net was established in raspberry, blackberry (Rubus fruticosus L.), strawberry (Fragaria × ananassa Duch.) and blueberry (Vaccinium corymbosum L.) orchards of an organic farm located in the department of Famaillá (Tucumán province). McPhail traps baited with apple cider vinegar were placed in the crop canopy. The traps were served weekly in summer and fortnightly in autumn. To determine fruit infestation by Z. indianus, mature healthy fruit were harvested from plants located near the traps, placed in plastic trays with cotton and absorbent paper on the bottom and were incubated in the laboratory at 60-65% RH and room temperature, to promote the emergence of Z. indianus adults. The first catches were recorded in traps from raspberry orchards in March 2021, with peaks in April (1.35 flies trap^‑1 day^‑1, FTD). Catches were significantly higher in traps from raspberry (0.40 FTD) and blackberry (0.28 FTD) than in traps from blueberry (0.03 FTD) and strawberry (0.00 FTD). The first fruit infestations were recorded in November 2020 in strawberries. The highest infestation was recorded in April 2021 in blackberry and raspberry with 0.29 and 0.65 flies g^‑1 of fruit, respectively. These results warn about the risk that this invasive frugivorous species represents for the berry industry of northern Argentina.