How to Manage Pests

UC Pest Management Guidelines

Small Grains

Corn Leaf Aphid

Scientific name: Rhopalosiphum maidis

(Reviewed 2/07, updated 2/09, pesticides updated 7/16)

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 per acre REI‡ PHI‡
(Example trade name)   (hours) (days)

UPDATED: 7/16
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
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. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. DIMETHOATE
  (Dimethoate 4EC) 0.5–0.75 pt 48 35
  MODE-OF-ACTION GROUP NUMBER1: 1B
  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.
 
B. MALATHION
  (Malathion 8) 1 pt 12 7
  MODE-OF-ACTION GROUP NUMBER1: 1B
  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.
 
C. 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 two applications per crop. See label for other restrictions. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. Avoid drift and tailwater runoff into surface waters.
 
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).

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Small Grains
UC ANR Publication 3466

Insects and Mites

L. D. Godfrey, Entomology, UC Davis
V. M. Barlow, UC Cooperative Extension, Riverside County and UC IPM Program

Acknowledgment for contributions to Insects and Mites:
D. Gonzalez, Entomology, UC Riverside
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier

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