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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Corn leaf aphid adults and nymphs.

Small Grains

Corn Leaf Aphid

Scientific name: Rhopalosiphum maidis

(Reviewed 2/07, updated 2/07)

In this Guideline:

DESCRIPTION OF THE PEST    Key to identifying aphids

Corn leaf aphids are small aphids that are bluish green to dark olive in color, with a purplish patch around the base of the cornicles. Because of its small size and short antennae, it could be confused with the Russian wheat aphid. Corn leaf aphid, however, has prominent black cornicles and lacks a supracaudal process.

DAMAGE

Damage is usually minor. Corn leaf aphid is a vector of BARLEY YELLOW DWARF virus.

MANAGEMENT

Biological Control
Corn leaf aphid is attacked by the usual predators and parasites (see APHIDS–GENERAL CONSIDERATIONS).

Monitoring
Check for corn leaf aphid when evaluating the field for other aphid species.

Management Decisions
Corn leaf aphid seldom requires treatment.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)
The following materials are listed in order of usefulness in an IPM program, taking into account impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact.
 
A. METHYL PARATHION*
  (Penncap M) 1–2 pt 5 days 15
  MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
  COMMENTS: May be used on wheat, barley, and oats. 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 35
  MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
  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: An organophosphate (Group 1B)1 insecticide.
  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) 0.25–0.5 lb 48 7
  MODE OF ACTION: A carbamate (Group 1A)1 insecticide.
  COMMENTS: May be used on barley, oats, rye, and wheat. 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: An organophosphate (Group 1B)1 insecticide.
  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 Modes of action are important in preventing the development of resistance to pesticides. 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. 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 is 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 the insect and mite section:
D. Gonzalez, Entomology, UC Riverside

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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