How to Manage Pests

UC Pest Management Guidelines

Citrus

Aphids

Scientific Names:
Black citrus aphid: Toxoptera aurantii
Cotton or melon aphid: Aphis gossypii
Spirea aphid: Aphis spiraecola

(Reviewed 9/08, updated 6/13)

In this Guideline:


Description of the Pests

The most common aphid on citrus in the coastal and intermediate districts of southern California is the spirea aphid. In the San Joaquin Valley, the cotton or melon aphid is the most commonly found aphid on citrus. The three species can be distinguished by color: spirea aphids are always green whereas the cotton aphid can range in color from yellow, to green, to dull black. A colony of cotton aphids is usually composed of several different color forms. Black citrus aphids are, as their name suggests, black.

Damage

Aphids feed on buds and on the underside of leaves (mainly feather growth), causing leaves to curl toward the stem. Spirea aphid, black aphid and cotton aphid can all transmit citrus tristeza virus. Insecticide applications for aphids are not recommended because it is difficult to prevent transmission of citrus tristeza virus by controlling aphids with insecticides unless an area wide treatment program is conducted.

Management

Aphids are generally not a problem on citrus except on young trees or continually flushing varieties (varieties that continually have new leaf growth), because their numbers decline when the foliage hardens off. Natural enemies normally control aphid populations and an insecticide application is rarely warranted. Treatment of aphids to prevent transmission of tristeza virus has been shown to be effective only if conducted over a large area (several miles in each direction) because aphids can fly long distances.

Biological Control

A number of coccinellid and syrphid predators, parasites, and fungal diseases usually keep aphid populations below damaging levels. A moderate aphid population (about 40% of growth flushes infested) can be considered beneficial on mature trees because aphids and their honeydew provide a good food source for natural enemies of other pests early in the season when other hosts are not available.

Organically Acceptable Methods

Biological control is acceptable on organically managed citrus.

Resistance

Populations of cotton aphids in the San Joaquin Valley have been shown to have resistance to organophosphate, carbamate, and pyrethroid insecticides.

Treatment Decisions

On newly established trees and on new growth flushes on mature trees, it is not uncommon for aphids to cause curling of leaves and produce honeydew. Treatment is usually not warranted because citrus can tolerate extensive leaf curling without yield effects. Pesticide applications are reserved for special situations such as areawide treatment programs.

Common name Amount to use R.E.I.‡ P.H.I.‡
(example trade name) (type of coverage)** (hours) (days)

  Calculate impact of pesticide on air quality

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. ACETAMIPRID
  (Assail 70WP) 1.1–2.3 oz/100 gal (OC) 12 7
  (Assail 30SG) 2.5–5.5 oz/100 gal (OC) 12 7
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 4A
 
B. THIAMETHOXAM
  (Actara) 5.5 oz/100 gal (OC) 12 0
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 4A
 
C. SPIROTETRAMAT
  (Movento) 10 oz/100 gal (OC) 24 1
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: predatory mites
  PERSISTENCE: Pests: long; Natural enemies: short
  MODE OF ACTION GROUP NUMBER1: 23
  ...PLUS...

NARROW RANGE OIL
  (415) 1% See comments See comments
  RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE OF ACTION: Contact including smothering and barrier effects; also improves translaminar movement and insecticide persistence. When tank mixing use the R.E.I and P.H.I of spirotetramat.
 
D. IMIDACLOPRID
  (Admire Pro, generics) 7 fl oz 12 0
  RANGE OF ACTIVITY: Pests: narrow (aphids, citrus leafminer, glassy-winged sharpshooter); Natural enemies: predatory beetles and parasites
  PERSISTENCE: Pests: long; Natural enemies: intermediate
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: For use on all varieties. Apply when root growth is occurring (June–September). Apply to soil; remains effective for 2 to 3 months. Requires 3 to 4 weeks for uptake into mature citrus to begin to kill pests. Pre-wet soil before treatment is applied. Very toxic to bees; do not apply during bloom because bees may be drawn to irrigation water.
 
** OC - Outside coverage uses 100–250 gal water/acre.
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 ("un"=unknown or uncertain mode of action) 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: Citrus
UC ANR Publication 3441

Insects, Mites, and Snails

  • E. E. Grafton-Cardwell, Entomology, UC Riverside and Kearney Agricultural Center, Parlier
  • J. G. Morse, Entomology, UC Riverside
  • N. V. O'Connell, UC Cooperative Extension, Tulare County
  • P. A. Phillips (emeritus), UC IPM Program, UC Cooperative Extension, Ventura County
  • C. E. Kallsen, UC Cooperative Extension, Kern County
  • D. R. Haviland, UC Cooperative Extension, Kern County
Acknowledgments for contributions to Insect, Mites, and Snails:
  • J. Barcinas, E.S.I., Corona, CA
  • R. Dunn, Badger Farming Co., Exeter, CA
  • J. Gorden, Pest Management Associates, Exeter, CA
  • H. Griffiths, E.S.I., Corona, CA
  • D. Machlitt, Consulting Entomology Services, Moorpark, CA
  • C. Musgrove, retired entomologist, Riverside, CA
  • K. Olsen, S & J Ranch, Pinedale, CA
  • T. Roberts, E.S.I., Corona, CA
  • T. Shea, UC Cooperative Extension, Riverside County
  • J. Stewart, Pest Management Associates, Exeter, CA
  • P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA

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