Agriculture: Small Grains Pest Management Guidelines


  • Schizaphis graminum
  • Description of the Pest

    Key to identifying aphids

    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.


    Biological Control

    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.

    Management Decisions

    If greenbug is present in large numbers and discoloration is evident before tillering, apply an insecticide.

    Common name Amount per acre REI‡ PHI‡
    (Example trade name) (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
      (Dimethoate 4EC) 0.5–0.75 pt 48 35
      COMMENTS: For use on wheat and triticale only. Do not make more than two applications per year. Do not graze within 14 days. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
      (Malathion 8) 1 pt 12 7
      COMMENTS: May be used on wheat, barley, oats, and rye. If alfalfa is in bloom, apply during the night or early in the morning when bees are not foraging in the field. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
    Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI; the longer of these two intervals is the minimum time that must elapse before harvest may take place.
    * Permit required from county agricultural commissioner for purchase or use.
    1 Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).
    Text Updated: 02/09
    Treatment Table Updated: 07/16