Summary The leaf miner Lasioptera donacis Coutin (Diptera: Cecidomyiidae) is a biological control agent of the invasive weed, Arundo donax L. (Poaceae), that was approved for release in the U.S. and Mexico. Pupae are preferred for shipment of living material to quarantine facilities. There is a question of whether emerged females would carry conidia of a potential mutualist fungus, and in particular the saprophyte Arthrinium arundinis, from the pupa or if they would have to acquire the conidia exclusively from the plant to start the oviposition process. We artificially smeared leaf-sheaths of growing plants with A. arundinis before being exposed to female midges, and maintained these host plants until the pupal stage of the midge developed. Polymerase chain reaction methods were applied to detect A. arundinis and any other potential fungi in these pupae. Only 9% of the pupae were infested by fungi or yeast, predominantly belonging to the genus Sarocladium, but not A. arundinis, confirming that the newly emerged females are free of this fungus and will have to acquire conidia present on the leaf-sheath for successful oviposition. We also tentatively tested by PCR for the presence of parasitic nematodes in these pupae. More than 42% of the pupae were shown to be infested specifically by T. gyraloura. Such high infection rate calls for developing methods to eliminate this parasite or to find a parasitefree native population prior to release of L. donacis adults in North America for biological control of A. donax. © 2018 E-flow BioOne. All rights reserved.