Emergence Pattern of Sorghum Midge and its Major Parasitoids on Midge-resistant and Susceptible Genotypes

Abstract

Studies were conducted on the species composition of parasitoids of sorghum midge, Stenodiplosis sorghicola Coquillett (Diptera: Cecidomyiidae), emergence pattern and level of parasitism. They took place at the International Crops Research Institute for the Semi-Arid Tropics Asia Centre using three midge-resistant (ICSV 745, ICSV 89058 and IS 10712) and three susceptible (Swarna, CSH 9 and ICSV 112) genotypes during the 1992-93 post-rainy and 1993 rainy seasons. The species of parasitoids collected were Aprostocetus gala Walker, A. coimbatorensis Rohwer (Hymenoptera: Eulophidae) and Eupelmus spp. (Hymenoptera: Eupelmidae). The species composition varied with the season, but was unaffected by varietal resistance and susceptibility to the midge. Although both species of Aprostocetus were present in rainy and post-rainy seasons, A. gala was predominant during the rainy season whereas A. coimbatorensis was predominant in the post-rainy season. There was no significant difference in the pattern of parasitoid emergence or the level of midge parasitization between resistant and susceptible genotypes. These results indicate that resistance to midge in the genotypes studied was not antagonistic to parasitoid activity, and that there is potential to interface biological control with host-plant resistance in the management of this insect.