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How to Manage Pests

UC Pest Management Guidelines


Winged adult greenbug.

Small Grains

Greenbug

Scientific name: Schizaphis graminum

(Reviewed 2/07, updated 2/09)

In this Guideline:


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.

DAMAGE

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.

MANAGEMENT

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.

Monitoring
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/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, information relating to natural enemies and honey bees as well as the environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. METHYL PARATHION*
  (Penncap M) 1–2 pt 5 days 15
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: May be used on wheat, oats, and barley only. Do not graze within 15 days. This product is highly toxic to foraging bees, young hive bees, and brood. Do not apply to any field when bees are present or in the surrounding vicinity.
 
B. DIMETHOATE 4EC 0.5–0.75 pt 48 60
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: For use on wheat and triticale only. Do not make more than 2 applications/year. Do not graze within 14 days. Highly toxic to honey bees if bees are present at treatment time or within a day after.
 
C. MALATHION 8EC 1.25 pt 12 7
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: May be used on wheat, barley, oats, rye. If alfalfa is in bloom, apply during the night or early in the morning when bees are not foraging in the field.
 
D. METHOMYL*
  (Lannate SP) 0.25–0.50 lb 48 7
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: May be used on wheat, barley, oats, and rye. Do not graze within 10 days. Do not apply more than 1.8 lb a.i./acre/crop. Highly toxic to honey bees if bees are present at treatment time or within a day after.
 
E. CHLORPYRIFOS*
  (Lorsban) 4E 0.5–1 pt 24 28
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: For use on wheat only. Do not make more than 2 applications/crop. See label for other restrictions. Highly toxic to honey bees if bees are present at treatment time or within a day after. Avoid drift and tailwater runoff into surface waters.
 
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I.; 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). For additional information, see their Web site at http://www.irac-online.org/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Small Grains
UC ANR Publication 3466
Insects and Mites
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
L. D. Godfrey, Entomology, UC Davis
Acknowledgment for contributions to Insects and Mites:
D. Gonzalez, Entomology, UC Riverside

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