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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Green peach aphid colony.

Tomato

Green Peach Aphid and Other Early-season Aphids

Scientific Names: Myzus persicae and others

(Reviewed 1/08, updated 1/08)

In this Guideline:

DESCRIPTION OF THE PESTS

The green peach aphid and several other species are most commonly found on tomatoes early in the season. The green peach aphid is slender, dark green to yellow, with indefinite darker stripes on the abdomen, and no waxy bloom. This aphid is primarily an early-season pest and may transmit virus diseases to tomatoes.

DAMAGE

Green peach aphid infestations may result in wilting, but this damage is usually not of great concern unless the crop is water-stressed or temperatures are extremely high. Research indicates that early-season infestations may delay maturity but usually do not result in yield loss unless other factors are also present that enhance the injury. More importantly, these aphids vector diseases such as alfalfa mosaic and tomato yellow top. Treatment may be warranted when nearby alfalfa fields are not certified as virus-free. Virus transmission has been observed when alfalfa is part of interplants of floral mixtures used to attract beneficials.

MANAGEMENT

Conserve natural enemies by avoiding early-season use of disruptive insecticides. If virus transmission is a major concern, it may be economical to reduce or delay the early-season influx and buildup of aphid populations with the use of reflective mulches in fresh market tomatoes. These aphids do not usually require treatment.

Biological Control
Many parasites and predators attack aphids. Among the more common predators are lady beetles and their larvae, lacewing larvae, and syrphid fly larvae. Populations of green peach aphids are reduced in winter by a parasitic fungus, Entomophthora aphidis. Many materials available for aphid control are highly disruptive of natural enemy populations. Make sure that insectary mixes that might be used do not contain alfalfa seed unless it is certified virus-free.

Cultural Control
Winged aphids are repelled by silver- or aluminum-colored mulches. If there is a probability of severe virus pressure, place reflective polyethylene mulches on planting beds before seeding or transplanting to significantly reduce rate of colonization by winged aphids and delay the buildup of damaging numbers of aphids by 4 to 6 weeks. While this approach is mainly effective in delaying or reducing the incidence of virus diseases transmitted by winged aphids and whiteflies, reflective mulches can also delay the buildup of wingless aphids that arise as a result of colonization by winged individuals. The mulches lose their effectiveness when more than 60% of the surface is covered by foliage. Therefore, they are effective only for the first few weeks after seedling emergence or transplanting of either spring or fall tomatoes.

Organically Acceptable Methods
Cultural and biological controls and sprays of insecticidal soap, pyrethrin, or thyme oil are acceptable for use on organically certified produce.

Monitoring and Treatment Decisions
Green peach aphids may move into early-season tomato seedlings but rarely require treatment. Early-season aphids have many natural enemies, including lady beetles, lacewings, syrphids, and parasites that frequently bring them under control later in the season. Sulfur materials do not control aphids and can cause phytotoxicity when applied to tender plants or under hot temperatures.

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 efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact.
 
A. PYMETROZINE
  (Fulfill) 2.75 oz 12 0
  MODE OF ACTION GROUP NUMBER1: 9B
  COMMENTS: Thorough spray coverage is essential for good control. Do not exceed 5.5 oz of product/acre/crop. Allow at least 7 days between applications.
 
B. ACETAMIPRID
  (Assail) 70WP 1.2 oz 12 7
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Allow 7 days between applications with a maximum of 4 applications/season.
 
C. OXAMYL*
  (Vydate) L 2–4 pt 48 3
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Do not use if psyllids are in the field as carbamates tend to promote development of their populations.
 
D. LAMBDA-CYHALOTHRIN*
  (Warrior with Zeon) 2.56–3.84 fl oz 24 5
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: For suppression only. Follow label guidelines for resistance management. Do not use this product if leafminers are present because it is destructive of their parasites.
 
E. IMIDACLOPRID
  (Admire Pro) 7–10.5 fl oz 12 21
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Effective against all early season aphid species. Most effective when soil or drip applied before or soon after transplanting. Do not apply to vegetables grown for seed.
 
F. DIMETHOATE
  (Dimethoate) E267 1.5 pt 48 7
  (Dimethoate 400) 1 pt 48 7
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not use this product if leafminers are present because it is destructive of their parasites.
 
G. MALATHION Label rates 12 1
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not use this product if leafminers are present because it is destructive of their parasites.
 
H. ENDOSULFAN*
  (Thionex) 3EC 0.66 qt 24 2
  MODE OF ACTION GROUP NUMBER1: 2A
  COMMENTS: Ground application recommended. Availability in many areas limited because of label restrictions for fields near waterways.
 
I. PYRETHRIN#
  (PyGanic) 1.4EC Label rates 12 0
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Short residual material; always buffer pyrethrin to pH 5.5 or lower.
 
J. THYME OIL#
  (Proud) Label rates 0 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Short residual material. Research has not been conducted against green peach aphid in California, but it has been shown to be effective against melon aphid.
 
K. INSECTICIDAL SOAP# 2.5 oz/gal water 12 0
  (M-Pede)
  MODE OF ACTION: A contact insecticide with smothering and barrier effects.
  COMMENTS: Can be used to reduce less than damaging populations, particularly when parasite activity is noted. Control is insufficient, however, when there is a high risk of virus transmission.
 
 
**  See label for dilution rates.
+ 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 until harvest can take place. 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.
# 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/.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
Insects and Mites
F. G. Zalom, Entomology, UC Davis
J. T. Trumble, Entomology, UC Riverside
C. F. Fouche, UC Cooperative Extension, San Joaquin Co.
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
Acknowledgments for contributions to the insects and mites section:
N. C. Toscano, Entomology, UC Riverside

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