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How to Manage Pests

UC Pest Management Guidelines


Green peach aphids.

Lettuce

Green Peach and Potato Aphids

Scientific Names:
Green peach aphid: Myzus persicae
Potato aphid: Macrosiphum euphorbiae

(Reviewed 8/07, updated 10/09)

In this Guideline:


DESCRIPTION OF THE PESTS

The potato aphid and the green peach aphid are commonly found on lettuce; of the two, green peach aphid is the most important. Green peach aphids are dark green to yellow and have no waxy covering. The tubercles at the base of the antennae grow toward each other. Populations start on the lower leaves, move up the plant, and are spread evenly over the plant.

Potato aphids have both pink and green forms. This aphid is much bigger than the green peach aphid, and the adult has much longer cornicles and cauda. Potato aphid colonies are composed of adults with offspring closely clustered around them, usually on the youngest leaves. The potato aphid may occur alone, or in colonies with green peach aphid.

DAMAGE

High numbers of aphids can stunt seedlings or transplants and will contaminate heads bound for market. Green peach aphids vector several viruses that affect lettuce.

MANAGEMENT

Biological Control
The same general predators that attack other aphids also prey on green peach aphids. Epidemics of a disease caused by the fungus Entomophthora aphidis may also kill portions of the green peach aphid population under some conditions. Parasites, including Lysiphlebus testaceipes, Aphidius matricariae, and Aphelinus semiflavus, attack this pest. Natural enemies rarely provide adequate control of high field populations of the aphid in spring or fall crops.

Organically Acceptable Methods
Biological control and sprays of azadirachtin or insecticidal soaps are organically acceptable.

Monitoring
Check all areas of the field twice a week, but especially the edges, which are usually the first area to become infested. Since green peach aphid infestations are clumped, you will need to sample 25 plants per quadrant of a 40- to 80-acre field.

Management Decisions
If high populations develop on seedlings, treat as soon as plants appear stressed. On more mature plants, before heading, do not treat unless populations exceed 20 aphids per plant. If a significant percentage of plants are infested just prior to heading, treat to keep aphids from spreading into the center of the head where they are difficult to control. Continue monitoring to see whether another treatment is needed. Some populations of green peach aphid may be resistant to certain insecticides in your area; check with your farm advisor for more information.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to the impact on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. DIAZINON*
  (various products) Label rates 72 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Avoid drift and tailwater runoff into surface waters.
 
B. IMIDACLOPRID
  (Admire Pro) 7–10.5 oz 12 21
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Placement is critical; see label for information. Do not apply more than 0.38 lb a.i. of Admire Pro/acre/year.
  . . . or . . .
  (Provado 1.6F) 3.75 fl oz 12 7
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not apply more than 0.24 lb a.i. of Provado/acre/year.
 
C. AZADIRACHTIN#
  (Aza-Direct 1.2%) 8.3–40 oz 4 0
  (Agroneem) 0.15% 48 oz 4 0
  MODE OF ACTION GROUP NUMBER1: 18B
  COMMENTS: Restricted use product in an organically certified crop.
 
D. FLONICAMID
  (Beleaf 50SG) 2–2.8 oz 12 0
  MODE OF ACTION GROUP NUMBER1: 9C
 
E. SPIROTETRAMAT
  (Movento) 4–5 fl oz 24 3
  MODE OF ACTION GROUP NUMBER1: 23
 
F. INSECTICIDAL SOAP#
  (M-Pede) Label rates 12 0
  MODE OF ACTION: A contact insecticide with smothering and barrier effects.
 
G. ACETAMIPRID
  (Assail 70WP) 0.8–1.2 oz/acre 12 7
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Foliar application. Allow 7 days between applications with a maximum of 5 applications/season.
 
H. PYMETROZINE
  (Fulfill) 2.75 oz 12 7
  MODE OF ACTION GROUP NUMBER1: 9B
 
** Mix with enough water to provide complete coverage.
+ 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 REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown produce.
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: Lettuce
UC ANR Publication 3450
Insects and Other Arthropods
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Insects and Mites:
W. E. Chaney, UC Cooperative Extension, Monterey County
N. C. Toscano, Entomology, UC Riverside

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