Eugene E. Nelson, Bugwood.org
This aphid has a very complex life cycle and has been found on more than 800 plant species. Among vegetables the green peach aphid is most frequently found on peppers and cole crops.
Green peach aphid eggs are shiny, black and about half the size of a pencil point. The eggs are only found on the bark of fruit trees. Aphid nymphs appear very similar to the un-winged adult with yellowish-green pear-shaped bodies and black legs and antennae. The body of the winged form is much slimmer with large oval shaped clear wings. The winged form may also have black markings on its body. The rear of the green peach aphid has 3 extrusions of the body wall called cornicles.
The green peach aphid has a complicated life cycle. In a single growing season populations will have multiple asexual generations and one sexual generation while inhabiting both fruit trees and garden plants. The green peach aphid does not have a pupal stage; instead each nymphal stage appears more like the adult.
The green peach aphid overwinters as an egg stage on the bark of fruit trees, specifically peach, cherry, apricot and plum. Egg hatch occurs about the time of peach bloom. The green peach aphid has both a sexual and asexual form. The majority of reproduction occurs asexually by a process called pathogenesis where live young are produced. Development occurs very quickly, growing from neonate to adult in as few as 5 days. After 3 or 4 generations on fruit trees winged adults develop which disperse to other hosts including many vegetable crops. In Pennsylvania this dispersion occurs in late June and July. Generations developing on vegetable crops will have both winged and wingless adults and reproduce asexually. In late August winged forms will migrate back to fruit trees. Near the end of the growing season on fruit trees sexual forms of the green peach aphid appear for the first time. After mating the female green peach aphid will ovipost eggs on the bark of fruit trees. In total the green peach aphid may have 10 to 15 generations in a growing season.
The green peach aphid has piercing sucking mouthparts, and feeds by inserting these mouthparts into plant tissue and sucking out the sap. This injures plants in three ways. First, feeding interferes with proper nutrient transfer in the plant. Second, the green peach aphid can transmit over 100 plant diseases, including cucumber mosaic virus on peppers. Finally, aphids produce a large amount of excrement called honey dew because of its high sugar content. Honey dew sticks to the leaves and often becomes a substrate for fungus, which causes smutting of leaves and fruit.
Plants injured by aphid feeding will have leaves that appear curled, distorted and discolored. Small to medium sized aphid populations are easily overlooked. In some cases the first sign of infestation is distortion as a result of one of the mosaic viruses the aphids transmit. Other common signs are leaves that appear wet but are actually covered with honey dew and the presence of a black sooty fungus growing on the honey due. Aphid populations can increase very quickly and it is not uncommon under the right conditions to find hundreds of aphids per plant.
Aphid population levels are heavily influenced by temperature, rainfall, numbers of natural enemies present and pesticides application. Aphid outbreaks are most frequent in hot dry weather. While heavy rains will often reduce the aphid population below the economic threshold. When pesticides are applied care should be taken to select pesticides that are not damaging to natural enemies of aphids. Because aphids reproductive rate is greater than their natural enemies, incorrect pesticide use may contribute to aphid outbreaks by removing the natural enemies. Fields of peppers and Cole crops should be scouted for the green peach aphid throughout the year especially during hot dry weather and 5 days to a week after a pesticide application.