The braconid parasitoid Microctonus colesi was released in Story and Boone counties, Iowa, but not recovered from collected alfalfa weevils, Hypera postica. Sampled adult weevils were parasitized at an overall seasonal rate of 41.5% by Microctonus aethiopoides, although it had not been released in the immediate vicinity.
Mertins, James W.
"Notes on Microctonus Spp. (Hymenoptera: Braconidae) Introduced to Iowa Against the Alfalfa Weevil, Hypera Postica (Coleoptera: Curculionidae),"
The Great Lakes Entomologist, vol 17
Available at: https://scholar.valpo.edu/tgle/vol17/iss4/10