Hymenopterous Parasites of Biotype C Greenbug1 in the High Plains of Texas2

Abstract

The braconid wasp, Lysiphlebus testaccipes (Cresson) was the major primary parasite attacking Biotype C Schizaphis graminum (Rondani) on grain sorghum, johnsongrass, barley, wheat, oats, and rye in the High Plains of Texas in 1970. Other parasites reared from mummies of S. graminum collected on one or more of these grass hosts in the High Plains were the braconid, Diaeretiella rapae (M'lntosh.), a primary parasite, and the following hymenopterous hyperparasites: a cynipid, Charips sp.; two pteromalids, Pachyneuron siphonophorae (Ashmead) and Asaphes lucens (Provancher); and an encyrtid, Aphidencyrtus aphidivorus (Mayr). S. graminum is apparently a new host record for D. rapae . Another apparently new parasite record for S. graminum is that of the eulophid Tetrasticluis minutus (Howard), which is probably a secondary parasite of S. graminum . It was not recovered in the High Plains, but it did emerge from collections of parasitized S. graminum collected on grain sorghum in Hunt County, Texas. Seasonal parasitization, as determined by the appearance of mummies in the population of S. graminum on untreated grain sorghum, was a delayed density-dependent action; that is, percent parasitization by primary parasites reached a peak level (100%) about 4 weeks after the population of S. graminum had peaked. A large percentage of the mummies infested with primary parasites did not produce the adults of these parasites, however, because of the attack by hyperparasites, primarily Cliarips sp. and P. siphonophorae .