How to Manage Pests

UC Pest Management Guidelines


Green Peach Aphid

Scientific Name: Myzus persicae

(Reviewed 12/09, updated 6/12, pesticides updated 5/16)

In this Guideline:

Description of the Pest

The green peach aphid is rather slender in form, light green or yellowish in color. Winged adults of the green peach aphid are pale or bright green and black, with a large dusky blotch on the dorsum of the abdomen. The immature forms are yellow, pinkish, or pale green. The mature wingless forms are pale or bright green and have no waxy covering. The tubercles at the base of the antennae grow towards each other. Populations tend to start on lower leaves and move up the plant. The green peach aphid occurs throughout California and has a wide host range.


In desert areas, Watermelon mosaic virus, Zucchini yellow mosaic, and Papaya ringspot virus are transmitted chiefly by the green peach aphid. This aphid moves into melon fields in large numbers from surrounding vegetation, carrying viruses as it moves and feeds from one plant to another. In the San Joaquin Valley, cucumber mosaic, zucchini mosaic, and watermelon mosaic are often the most important viruses transmitted by this aphid.


Silver reflective mulches have successfully been used to repel aphids from plants, thus reducing or delaying virus transmission. In some areas of the state, row covers have also been successfully used. Biological control can have a significant impact on aphid population, so be sure to evaluate predator and parasite populations when making treatment decisions.

Biological Control

Naturally occurring populations of the convergent lady beetle, Hippodamia convergens, may provide effective control in early spring. Releases of this beetle are not effective, however, because it generally does not remain in the field following release. Other general predators, such as lacewing and syrphid larvae, and parasitic wasps, including Aphidius, Diaeretiella, and Aphelinus species, also attack aphids. Biological control is not effective in reducing virus transmission by this aphid.

Cultural Control
  • In desert production areas, exclude aphids by applying row covers at planting and removing them at first bloom or earlier. Do not apply row covers in the San Joaquin Valley.
    • Plastic row cover. Do not remove the entire cover at one time because the drastic reduction in humidity will shock plants and can lead to collapse. Instead, vent the covers and remove them piecemeal. If the air temperature under the row cover reaches 104°F remove them. Also remove the row cover before plants grow high enough to touch hot plastic.
    • Spun-bonded row cover. Covers made of spun-bonded materials do not need venting because hot air is able to escape.
  • Apply silver reflective plastic mulches at planting to repel aphids from plants, thereby reducing or delaying virus infection. Reflective mulches help plants get off to a healthy start, and are effective until expanding foliage covers the reflective surface. Remove mulches in the desert areas when summer temperatures are excessive for optimal growth of plants. However, in the Central Valley and cooler areas, mulches have not caused plant damage in the summer; in fact, they improve soil moisture and nutrient retention, which may further aid plant productivity.
  • Control weeds along ditch banks, roads, in farmyards, and other noncultivated areas that contribute directly to the aphid problem.
  • Planting a habitat for beneficial insects, such as sweet alyssum, around the field may be helpful.
  • Delay planting until warm temperatures (80° to 85°F) occur and the spring flight of aphids is over.
  • Do not overfertilize with nitrogen.
  • Fields infested with green peach aphid should be disced or plowed under as soon as harvest is complete.
Organically Acceptable Methods

Biological and cultural controls and applications of insecticidal soaps and certain narrow range oils are acceptable to use in an organically certified crop.

Monitoring and Treatment Decisions

Before planting seed or transplants, set out yellow sticky cards at field edges to monitor the movement of aphids and whiteflies into the crop. Start checking traps after transplanting or when seedlings emerge. When aphids are observed on traps, begin monitoring crop foliage.

The decision to apply insecticides for aphids is based mainly on visual counts; measurable thresholds have not been researched. It is important to treat early to ensure that the aphids do not build up to high levels. Early treatment does not prevent virus introduction; insecticides, however, may help reduce spread of the virus if aphid colonies are present. Be aware, however, that parasites and predators, if present, may prevent an infestation from becoming established throughout a field, thus eliminating the need for insecticides.

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

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.
  (Venom) See comments 12 See comments
  COMMENTS: Rates vary depending upon whether a soil or foliar application. Soil application preferred because it has less impact on natural enemies. Preharvest intervals: foliar application—1 day; soil—21 days.
  (Admire Pro) 7–10.5 fl oz 12 21
  COMMENTS: Apply at planting or transplanting and incorporate into root zone.
  (Platinum) 5–11 fl oz 12 30
  COMMENTS: At seeding or transplanting, apply in sufficient water to ensure uniform application and incorporation into the soil. Provides about 40 days of protection. Use where field has history of these pests.
  (Fulfill) 2.75 oz 12 0
  (Dimethoate 2.67 EC) Label rates 48 3
  COMMENTS: Labeled for use on melons and watermelons only. Highly toxic to honey bees.
  (Hexacide) 0.75–1.5 qt 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Good coverage is essential for good control. Apply in a minimum of 25 gal/acre. Less disruptive of beneficials than the other organically acceptable alternatives listed.
  (M-Pede) 1–2% solution 12 0
  MODE OF ACTION: A contact insecticide with smothering and barrier effects.
  COMMENTS: This material will reduce populations temporarily, but has no residual and requires repeat applications and thorough coverage.
  (TriTek) 1–2 gal/100 gal 4 0
  (Organic JMS Stylet Oil) 3–6 qt/100 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Oil will reduce populations temporarily, but has no residual and requires repeat applications and thorough coverage. Oils may cause phytotoxicity problems; exercise care when using these materials. Check with certifier to determine which products are organically acceptable.
  (Lannate LV) 1.5–3 pt 48 See comments
  COMMENTS: Labeled for use on melons, cucumbers, and summer squash only. Apply early and as needed 7 days later. Repeated use of this material is very disruptive to beneficials. PHI is 1 day if 1.5 pt or less is used/acre; if over 1.5 pt, PHI is 3 days.
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 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).
# Acceptable for use on organically grown produce.
Not recommended or not on the label.
* Permit required from county agricultural commissioner for purchase or use.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cucurbits
UC ANR Publication 3445

Insects and Mites

E. T. Natwick, UC Cooperative Extension, Imperial County
J. J. Stapleton, UC IPM Program, Kearney Agricultultural Center, Parlier
C. S. Stoddard, UC Cooperative Extension, Merced & Madera counties

Acknowledgment for contributions to Insects and Mites:
R. L. Coviello, UC Cooperative Extension, Fresno County
C. B. Fouche, UC Cooperative Extension, San Joaquin County
L. D. Godfrey, Entomology, UC Davis
J. B. LeBoeuf, AgiData Sensing, Inc., Fresno
M. Murray, UC Cooperative Extension, Colusa and Glenn counties
C. G. Summers, Entomology, UC Davis and Kearney Agricultural Center, Parlier

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