Role of Indigenous Coccinellids in Regulating Greenbugs (Homoptera: Aphididae) on Texas Grain Sorghum

Abstract

The effectiveness of the native coccinellid predators of the greenbug, Schizaphis graminum (Rondani), was determined in Texas high plains grain sorghum using exclusion techniques. The most abundant greenbug predators encountered were Hippodamia convergens (Guerin-Meneville) and H. sinuate (Mulsant). Natural enemies showed no significant suppressive capacity during the early portion of the growing season, though both Hippodamia species were frequently observed. Selective exclusion of adult Hippodamia spp. and larger predators demonstrated the efficacy of these enemies throughout the latter portion of the growing season. Introduction of the two coccinellid species into cages excluding all enemies indicated their capacity to reduce greenbug density in light or moderate greenbug infestations. Regulation of greenbugs in Texas high plains grain sorghum is largely due to the suppressive action of Hippodamia spp., not the common greenbug parasites of the region.