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Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/5/2005 Publication Date: 12/1/2005 Citation: Shanower, T.G. 2005. Occurrence of Sitodiplosis mosellana (Diptera: Cecidomyiidae), and its parasitoid, Macroglenes penetrans (Hymenoptera: Platygasteridae), in northeastern Montana. The Canadian Entomologist. 137:753-755. Interpretive Summary: The wheat midge is an infrequent but devastating pest that has been present in western North America for at least 100 years. This paper is the first report of the wheat midge and a key natural enemy from Montana. Annual surveys were conducted in four counties of northeastern Montana for five years collecting wheat midge larvae that overwinter in the soil. In addition, infested wheat heads were collected from 10 fields, and wheat midges and parasitoids were reared. The wheat midge was found in all four counties, though at relatively low levels. Densities fluctuated across years and locations, with the highest densities of midge larvae occurring in Sheridan and Roosevelt counties. The natural enemy was found at all 10 sample sites and constituted up to 52% of the emerged adults. Northeastern Montana and northwestern North Dakota produce the majority of the US durum crop, which is particularly susceptible to the wheat midge. Despite the low densities of the wheat midge, and the presence of at least one natural enemy, producers and extension personnel in these counties should be aware of the damage potential of this pest. Annual soil sampling combined with monitoring adult populations at identified hotspots would provide information for making appropriate pest management decisions. Technical Abstract: The wheat midge, Sitodiplosis mosellana (Ghin) (Diptera: Cecidomyiidae), is an infrequent but devastating pest that has been present in western North America for at least 100 years. This is the first published report of the presence of the wheat midge and its parasitoid Macroglenes penetrans in Montana. Annual surveys were conducted in four counties of northeastern Montana for five years using a systematic soil sampling method to collect overwintering wheat midge larvae. In addition, in 2004, infested wheat heads were collected from 10 fields, and wheat midges and parasitoids were reared. The wheat midge occurred in all four counties, though at relatively low levels. Densities fluctuated across years and locations, with the highest densities of overwintering midge larvae occurring in Sheridan and Roosevelt counties. Macroglenes penetrans was found at all 10 sample sites and constituted up to 52% of the emerged adults (midges + parasitoid). Northeastern Montana and northwestern North Dakota produce the majority of the US durum crop, which is particularly susceptible to the wheat midge. Despite the low densities of the wheat midge, and the presence of at least one natural enemy, producers and extension personnel in these counties should be aware of the damage potential of this pest. Annual soil sampling combined with monitoring adult populations at identified hotspots would provide the information needed to make appropriate pest management decisions while minimizing sampling time. |
