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UC Pest Management Guidelines


Bean plant heavily infested with cowpea aphids.

Dry Beans

Aphids

Scientific names:
Cowpea aphid: Aphis craccivora
Bean aphid: Aphis fabae
Pea aphid: Acyrthosiphon pisum
Green peach aphid: Myzus persicae

(Reviewed 8/07, updated 12/08)

In this Guideline:


DESCRIPTION OF THE PESTS

The two most common species encountered on beans are the cowpea aphid and the bean aphid. The cowpea aphid, which is also common on black-eye beans (cowpeas), is shiny black with legs and antennae that are white to pale yellow with black tips. The bean aphid is slightly larger than the cowpea aphid, and dark olive-green to black with light-colored legs. The pea aphid is a relatively large, green, somewhat shiny aphid.

DAMAGE

Aphids damage plants by: (1) sucking plant sap which causes heavily infested leaves to curl and stunts plants; (2) excreting honeydew which causes sticky, shiny leaves to ultimately turn black because of a sooty-mold fungus growth; and (3) spreading plant diseases (a large number of viruses are vectored by aphids). Infestations frequently are localized with heavily infested leaves curled downward.

MANAGEMENT

Be sure to assess levels of biological control when evaluating aphid populations. Frequently, parasites and predators prevent aphid infestations from becoming established throughout a field. Temperatures greater than 85°F frequently inhibit buildup of large densities of pea and green peach aphids.

Biological Control
Common predators of aphids in beans include lady beetles, syrphid flies, and lacewings. Parasitic wasps attack each of the common aphid species, turning them into hard, crusty mummies.

Organically Acceptable Methods
Biological control is organically acceptable.

Monitoring and Treatment Decisions
Aphid control in beans is not always necessary. The decision to treat for aphids is based mainly on visual inspection and the stage of crop development. Measurable thresholds are not available. Begin inspecting for aphid problems along with other pests and their damage when the crop emerges. Continue looking through the vegetative growth and flower bud to bloom periods.

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. MALATHION 8 EC 1.5 pt 12 1
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Highly toxic to honey bees; do not apply when bees are present.
 
B. DIMETHOATE 1–1.5 pt 48 0
  2.67 lb/gal EC
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Ground or air application. Highly toxic to honey bees; do not apply when bees are present.
 
** Mix with sufficient water to obtain full 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.
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/.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Dry Beans
UC ANR Publication 3446
Insects and Mites
L. D. Godfrey, Entomology, UC Davis
R. F. Long, UC Cooperative Extension, Yolo County

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