We expect to find that the blue aphids have been parasitized by Aphelinus species wasps. These tiny wasps can, over time, play a significant role in reducing aphid populations. The species affecting the sugarcane aphid is unknown, but Dr. Jim Woolley (College Station) and Dr. Mike Brewer (Corpus Christi) are working on the identification.
Blue parasitized sugarcane aphids among non-parasitized aphids.
Photo credit: Charles Allen
Here is a short video by Karla Cruz of an Aphelinus wasp laying an egg in a sugarcane aphid.