How to Manage Pests
UC Pest Management Guidelines
Scientific name: Schizaphis graminum
(Reviewed 2/07, updated 2/09, pesticides updated 7/16, corrected 7/19)
In this Guideline:
The greenbug is a green to yellow-green aphid with a dark green stripe down the middle of its back. It can be distinguished from the Russian wheat aphid by its longer antennae, long tube-shaped cornicles, and the lack of a supracaudal process. Greenbug is most easily confused with the rose-grain aphid. However, the antennae of the greenbug are uniformly dark while those of the rose-grain aphid are darker only at each joint. Rose-grain aphid has eight or more hairs on the cauda while greenbug only has four; a microscope is needed to see these hairs.
Like the Russian wheat aphid, greenbug injects a toxin into the plant while feeding. Injury appears as yellowish spots or patches on the leaves. In some cases, discolored areas show reddish or brown. The entire leaf or plant turns yellow as populations increase. Generally plants are damaged only if significant feeding occurs before tillering. Damage is more likely in the Imperial Valley but can occur in the San Joaquin Valley as well.
Greenbug is a vector of BARLEY YELLOW DWARF virus.
Greenbug is attacked by several natural enemies (see APHIDS - GENERAL CONSIDERATIONS). Look for evidence of parasites (bloated mummies) and also for lady beetles, green lacewings, and syrphid fly larvae.
Fields should be checked regularly from seedling emergence to tillering. If discoloration is present be sure to check for the presence of the aphid. If you are not sure if the aphids are greenbug or rose-grain aphid, contact your farm advisor before applying any chemicals.
If greenbug is present in large numbers and discoloration is evident before tillering, apply an insecticide.
UC IPM Pest Management Guidelines:
Insects and Mites
L. D. Godfrey, Entomology, UC Davis
Acknowledgment for contributions to Insects and Mites:D. Gonzalez, Entomology, UC Riverside
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier