Sorghum midge and midge parasitism on Johnsongrass

Johnsongrass, Sorghum halepense L., in the soft dough stage was the optimal spikelet developmental stage for monitoring sorghum midge and its hymenopterous parasites in johnsongrass. The soft dough stage contained the greatest percentage of late instar sorghum midge, Contarinia sorghicola (Coquillett) and hymenopterous larvae and pupae. The parasite, Tetrastichus near blastophagi (Ashmead) emerged significantly earlier than midge parasites Eupelmus popa Girault, Aprostocetus diplosidis Crawford, or T. near venustus Gahan. Mean emergence times for E. popa, A. diplosidis, and T. near venustus were not significantly different from each other. T. near blastophagi was obtained only from pedicellate spikelets, whereas midges and the other three collected parasites were obtained from both pedicellate and sessile spikelets