Egg - Approximately 0.85 mm long, the light green egg turns a shiny black before hatching. The egg stage does not occur in North Carolina.
Nymph - The immature aphid is smaller than but similar to the larger wingless adult. It requires four molts to reach the adult stage.
Host Plants - Pea aphids infest garden, field, and sweet peas, sweet clover, alfalfa, and some leguminous weeds. Vetch and crimson clover are important overwintering hosts.
Damage - Pea aphids extract sap from the terminal leaves and stem of the host plant. They also feed on pods causing them to curl, shrink, and partially fill. Their feeding can result in deformation, wilting, or death of the host depending upon the infestation level and size of the plant. Plants less than 15 cm (6 in) high are easily killed by a few aphids, whereas larger plants are only slightly damaged. Plants are often coated with shiny honeydew secreted by aphids, and cast skins may give leaves and ground a whitish appearance. These aphids also transmit pea enation mosaic and yellow bean mosaic viruses. The first of these viruses, pea enation mosaic, has been a problem in New York but has not been reported in North Carolina.
Life History - In North Carolina, wingless female pea aphids continue to feed and breed throughout the winter months. In spring, aphid activity increases. Each adult female gives birth to 10 to 14 nymphs each day until she has produced about 100 offspring. Nymphs mature into adults in 10 to 14 days. Most nymphs develop into wingless female adults. However, when overcrowding occurs, winged aphids develop, migrate to other host plants, and establish new colonies. Since generations overlap and reproduction continues all year, the number of annual generations is difficult to determine. The pea aphid thrives best and reproduces most rapidly at temperatures around 18 degrees C (65 F) and humidities near 80 percent.
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