Diversity and seasonal abundance of sorghum panicle-feeding Hemiptera in South Africa

During the past two decades, panicle-feeding Hemiptera (head bugs) became serious pests of sorghum in West and Central Africa. Of the more than 100 sorghum insect pests reported in Africa, 42 species are reported to be panicle-feeding pests. Prior to this study, no research had been done on the panicle-feeding Hemiptera in South Africa. The objectives of the study were to determine the abundance and diversity of panicle-feeding Hemiptera on sorghum. Surveys were conducted between November 2004 and June 2006 at 26 sites in four provinces of South Africa. Collection was done using a plastic bag method and a D-Vac. A checklist was compiled and the temporal distribution of different Hemiptera species determined during panicle development. The total number of adults and nymphs collected during this study was 23,798. Thirty-nine herbivorous Hemiptera species were collected. The most abundant family was the Miridae followed by the Lygaeidae, which made up 41% and 17%, respectively, of the total number of individuals. Eurystylus bellevoyi, Campylomma sp., Creontiades pallidus, Nysius natalensis, Nezara viridula and Sthenaridea suturalis were the most abundant species and also occurred widely in the sorghum production area. Infestation levels of these species were generally low compared with those in other parts of Africa, but comparatively high infestation levels were observed at some sites. There was no clear distinction between the different panicle development stages during which panicles were infested by different species. The general tendency was that nearly all species were present from the flowering stage onwards and that numbers declined when grain hardened.