Date of this Version
Four hymenopterous parasitoids of the sorghum midge, Contarinia sorghicola (Coquillet), were found in Burleson County, Texas: Eupelmus popa Girault, Tetrastichus near venustus Gahan, Tetrastichus near blastophagi (Ashmead), and Aprostocetus diplosidis Crawford. E. popa and A. diplosidis were ectoparasitic on the midge host in sorghum spikelets, while T. near venustus fed both externally and internally. Members of the parasitoid complex oviposited and developed to adults in spikelets containing 1- to 18-day-old immature midges, which corresponded to larval and pupal stages of midges. Most parasitoids developed from midges parasitized as mid-stage larvae. Developmental time from egg to adult emergence ranged from 7 to 32 days for the parasitoid complex. Emergence of most adults of the individual parasitoid species ranged from 15 to 19 days. This developmental time corresponded to that of the midge host, which emerged as adults in 15 to 18 days after oviposition. E. popa was most abundant during spring and early summer in both johnsongrass and sorghum. A. diplosidis reached its highest density in late summer and fall. T. venustus was primarily a mid-season parasitoid and T. blastophagi densities were relatively high during the spring and summer months. T. blastophagi showed a preference for sorghum midges infesting johnsongrass while T. venustus and A. diplosidis preferred midges infesting sorghum. Over the course of the season, 20.0 and 8.2% of sorghum midges were parasitized in johnsongrass and sorghum, respectively.