Switchgrass Gall Midge

Distinguished from congeners by leg pattern, hind tarsi white at tip and legs without horizontal light- and dark-banded scale covering on the legs. Alternatively, female eighth tergal sclerites no longer than the preceding tergite. A potentially economically signifigant pest of switchgrass. Abstract of Calles Torres 2013: Switchgrass ( Panicum virgatum L.) is considered to be a highly promising bioenergy crop. However, little is known about insect pests that impact its utilization for this purpose. The switchgrass gall midge [ Chilophaga virgati Gagné (Diptera: Cecidomyiidae)], which was first discovered in 2008 at Brookings, SD, USA, is shown to have a negative impact on biomass and seed yields of switchgrass. Our objectives were to increase knowledge of the biology of the midge by describing its life stages and any parasitoids that have biological control potential. Data collections were made during May to December in 2011 and April to late autumn in 2012. The gall midge adult is active from early June to late July. This insect overwinters as a late instar larva, usually in large aggregations, enclosed in the sheath of the flag leaf of dry tillers. The mean number of larvae was 31, with a range of 6 to 85 per tiller. Infested tillers m^-2 varied among three phenologically distinct cultivars. The late flowering cultivar ‘Cave-In-Rock’ was more heavily infested (>2×) than the early flowering ‘Dacotah’. A newly discovered parasitoid, Platygaster chilophagae Buhl (Hymenoptera: Platygastridae) and a species of Quadrastichus sp. (Hymenoptera: Eulophidae) were reared from gall midge larvae. These results will be valuable to entomologists, switchgrass breeders, and agronomists as a guide to the occurrence and activities of the gall midge.