[6] In the autumn, female pea aphids lay fertilized eggs overwinter that hatch the following spring.

[citation needed] Population densities are at their highest in early summer, then decrease through predation and parasitism.

Overcrowding and poor food quality may trigger the development of winged individuals in subsequent generations.

[8] It generally feeds on the lower sides of leaves, buds and pods of legumes, ingesting phloem sap through its stylets.

On crops such as peas and alfalfa, A. pisum is considered among the aphid species of major agronomical importance.

[5] Yields can be affected by the sap intake that directly weakens plants, although pea aphids seldom reach densities that might significantly reduce crop production.

Protection against pea aphids includes the use of chemical insecticides, natural predators and parasitoids, and the selection of resistant cultivars.

[8] The pea aphid is thought to be of Palearctic origin, but it is now commonly found worldwide under temperate climate.

Its host range in North America is very similar to that of the closely related blue alfalfa aphid (Acyrthosiphon kondoi).

Its reproductive cycle, including the sexual phase and the overwintering of eggs, can be easily completed on host plants under laboratory conditions, and the relatively large size of individuals facilitates physiological studies.

The pea aphid genome and other of its features are the focus of studies covering the following areas: A. pisum participates in an obligate endosymbiotic relationship with the bacteria Buchnera aphidicola.

[23][24] When treated with antibiotics to remove the Buchnera bacteria, A. pisum growth and reproduction are interrupted or reduced.

[27] Like other insects of the order Hemiptera, A.pisum utilizes an endosymbiotic bacterium to overcome the nutritional deficiencies of phloem sap.

In addition to these nine essential amino acids, A. pisum is unable to synthesize arginine due to missing urea cycle genes.

[24][33][37] A bacteriome is a specialized organ that runs along the length of the pea aphid on two sides of the body and joins near the hindgut.

[24][33][37] Bacteriocytes are located near the ovariole cluster and Buchnera cells are vertically transferred from the mother's ovaries through transovarial transmission.

[33] The A. pisum and Buchnera genomes have experienced unique modifications that are likely related to the establishment and maintenance of the endosymbiotic relationship.

[34] A. pisum specific gene duplications of amino acid transporters highly expressed in bacteriocytes have been observed.

Jointly, the genomes of these two organisms complement each other to produce complete metabolic pathways for the biosynthesis of nutrients such as amino acids and other essential molecules.

For example, A. pisum is the only species with a sequenced genome known to be missing key components of the purine salvage pathway, essential for the production of DNA, RNA, signaling molecules, and ATP.

Through this complementation, the nucleotide requirements of both organisms are fulfilled: the purine salvage pathway is completed for A. pisum and Buchnera receives necessary guanosine.

[13] The A. pisum genome lacks IMS, dFADD, Dredd and Retish genes that are a part of the IMD (immunodeficiency) pathway and present in other related insects.

A reduced immune system may have facilitated the establishment and sustained maintenance of the symbiotic relationship between the Buchnera bacterium and A.

[23][34] Also, phloem sap is a diet with reduced amounts of microbes which may have lower the evolutionary pressure of A. pisum to maintain the immune response pathway genes.