Green Peach Aphid

The green peach aphid is a medium-sized aphid that is slender in form. The wingless forms are pale green. At times, a pinkish form may be present. During cool weather, the colors may be slightly darker compared to during hotter times of the year.

Winged adults form under specific conditions of overcrowding or plant stress and disperse to other plants or fields. They are pale or bright green and black, with a large dusky blotch on the dorsum of the abdomen; wingless forms lack this dark patch. Both winged and wingless forms have prominent cornicles that are slightly swollen and clublike in appearance. The tubercles  at the base of the antennae lean towards each other.

The green peach aphid occurs throughout California and has a wide host range. Green peach aphid is most common in spring and fall but may be found at any time throughout the year.

The green peach aphid vectors more plant viruses than any other aphid, transmitting over 100 different virus diseases. It does not, however, vector Carrot mottle virus or Carrot red leaf virus.

High numbers can cause stunting and leaf curling and twisting. Aphid bodies, the honeydew they secrete, and the associated sooty mold can lead to an unmarketable crop.

Aphid survival and development are historically greatest during periods with temperatures less than 80°F.

Green peach aphid is attacked by a number of common predators and parasites, especially in fields that are not sprayed or sprayed with reduced-toxicity pesticides.

• Naturally occurring populations of the convergent lady beetle, Hippodamia convergens, may provide effective control in the early spring. Release of commercially purchased or harvested beetles is not effective, because they generally don't remain in the field following release.
• Other common predators include green lacewings, lady beetles, and syrphid fly larvae.
• Common aphid parasites include Lysiphlebus testaceipes, Aphidius matricariae, Aphelinus semiflavus, and Diaeretiella rapae. Some of these organisms are available from commercial sources and may be released for aphid control or they may be naturally present and provide control. Hedgerows or companion plants such as alyssum attract and provide food and shelter for these natural enemies that are then available to control aphids in the field. For more information about planting hedgerows, see Establishing Hedgerows on Farms in California, UC ANR publication 8390 (PDF).
• Green peach aphid is susceptible to the fungus Entomophthora aphidis that commonly attacks aphids.

Biological control is not effective in reducing virus transmission by this aphid.

Field sanitation is important in reducing the number of aphids in and around cilantro or parsley.

• Remove infested culls and weedy species around fields that may harbor the aphid between crops.
• Destroy crop residue immediately after harvest. Long-term rotation to other crops is advisable.
• Avoid other aphid-favored crops, such as lettuce, in adjacent upwind fields.

Intensify field monitoring for aphids when adjacent fields with aphid-favored crops are harvested or senesce (die).

Biological and cultural controls, applications of insecticidal soaps, certain narrow range oils, entomopathogenic fungi (such as Beauveria bassiana), azadirachtin (Neemix), and neem oil (Trilogy) are acceptable for use on organically certified cilantro and parsley.

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

• Monitor fields for aphids weekly during spring and summer by examining the upper and lower surfaces of leaves.
• Look for evidence of predators and parasites and their impact on aphid numbers.
• Sample several locations because infestations tend to be erratic in the field. Concentrate on field edges particularly where cilantro or parsley fields border harvested lettuce fields.

Small aphid colonies occasionally develop on cilantro or parsley leaves and may reach treatable levels, but no treatment threshold for green peach aphid on cilantro and parsley has been established.

High numbers of green peach aphid can kill young seedlings, so spray infested young plants if they show stress from feeding by this aphid. It is important to spray early to ensure that the aphids do not build up to high levels. Early insecticide application does not prevent virus introduction; however, insecticides may help reduce spread of the virus if aphid colonies are present. Be aware, that parasites and predators, if present, may prevent an infestation from becoming established throughout a field, thus eliminating the need for insecticides.

Green peach aphid has developed a high level of resistance to many pesticides and may be difficult to control.