Green Peach Aphids

What do peaches and potatoes have in common? The green peach aphid.

Considered the world’s worst disease vector among garden plants, green peach aphids (Myzus persicae) love to feed on peach and potato leaves, along with dozens of other garden plants.

Winged adult green peach aphid (Public Domain)

Green peach aphid description

Green peach aphids are generally found in colonies of winged and wingless adults and immature nymphs. Green potato aphids look a lot like potato aphids (Macrosiphum euphorbiae). While potato aphids can be seen throughout the plant, green peach aphids prefer hiding on the underside of leaves.

​Adults may be bright or pale green, with a dark patch on the back (dorsum). Nymphs are pale green, yellowish, or pale pink. Eggs are elliptical in shape and only 1/50” long. At first, eggs are green or yellow, but they soon turn black, making them nearly impossible to see. Green peach aphids have a rather bizarre lifecycle that is too complex for this venue. You can read an excellent summary about it at the University of Florida website, if you are interested in that sort of thing.

​Damage caused by green peach aphids

Green peach aphids often overwinter in the egg stage on stone fruits, particularly on peach and peach hybrids, though apricot and plum are also favored. In spring, these eggs hatch and nymphs begin feeding on buds, flowers, and new stems. A few generations later, which only takes a month or so, winged adults move to summer feeding areas. It would probably be simpler to list the garden plants that do not attract green peach aphids, but you do need to know where to look for these pests. 

Summer feeding can occur on artichoke, asparagus, beans, beets, broccoli, Brussels sprouts, cabbage, carrot, cauliflower, cantaloupe, celery, chili peppers, corn, cucumber, fennel, kale, kohlrabi, turnip, eggplant, lettuce, mustard,okra, parsley, parsnip, peas, peppers, potato, pumpkin, radish, spinach, squash, sunflowers, tomatoes, turnips, watercress, and watermelon.

Aphids prefer feeding on tender new growth. This leads to wilting, water-stress, and stunting. It also generates a lot of honeydew (sugary insect poop), which provides the perfect growth medium for sooty mold. Heavy aphid feeding can weaken a plant to the point of death. The bigger problem, as with nearly all aphid species, is that these pests carry diseases. Green peach aphids may infect plants with a variety of viral diseases, including:

• alfalfa mosaic, or calico
• beet yellows virus
• beet western yellows
• cauliflower mosaic
• cucumber mosaic
• lettuce mosaic
• net necrosis

• pepper mottle
• plum pox
• potato leafroll
• potato virus Y
• turnip mosaic viruses
• watermelon mosaic

If potato leafroll virus appears in your garden, it is a good idea to remove the infected plant, plus three other plants in every direction, to prevent green peach aphids from spreading the disease even further. This is yet another reason why it is so important to plant certified disease-free plants in the first place. These pests are often found in greenhouses, so placing new plants in quarantine can go a long way toward preventing an infestation. They can also travel on the wind, so it's a constant battle.

Green peach aphid management

The best way to control green peach aphids is to hit them in winter. This means removing overwintering sites, such as infested leaves, spent plant debris, and nearby weeds. Malva is a popular winter wonderland for aphids, so keep that weed away from your peach trees and potato plants. Bindweed, lambsquarters, penny cress, pigweed, sowthistle, tumbleweeds, white goosefoot, and rouge members of the nightshade family can also provide overwintering sites for this pest.

As spring and summer come around, however, you can attract and protect beneficial predators, such as lady bugs, lacewings, parasitic wasps, and syrphid flies, by providing fresh water, planting a variety of insectary plants, and avoiding the use of broad spectrum pesticides. Most chemicals designed to kill aphids cause more harm than help by disrupting the lifecycle of many natural predators. There is also a parasitic fungus (Entomophthora aphidis) that attacks aphids, but you can’t do anything about that one.

Early each June, in northern California, green peach aphids migrate into our gardens. You can prevent a full-blown infestation by monitoring plants on a weekly basis and using a damp rag or paper towel to wipe off colonies before they can really start propagating. A single female, hatched in spring, can reach sexual maturity in only 10 days, creating 20 generations in a single year. By the end of summer, this can result in billions of offspring.