Essentially all aphids, regardless of form, are female. Males, if they occur, are present only in late summer/early fall, during the last generation outdoors. The normal habit of aphids is for a female to give live birth to a genetically identical daughter aphid through asexual reproduction (parthenogenesis). The newly hatched aphid can develop rapidly, and is usually completed in about 10 to 14 days. Adults can typically produce three to five offspring per day over their lifetime, which can extend to about a month, but is usually shortened by natural enemy activities.
There is a change in the aphid life cycle to handle the challenge of winter, when plants are not active and cold temperatures would be lethal. In late summer, different forms of aphids are produced, including special male and female sexual forms. After mating, these females can lay eggs, and they typically lay eggs in cracks around shoots or on stems. This egg is the stage at which the aphid typically survives the winter during outdoor conditions in Colorado. The eggs hatch the following spring, shortly after crawler data emergence, and the normal life cycle resumes.
Some aphids have even more complicated life cycles that involve alternating between host plants. With these species, eggs are laid at the end of the growing season on a tree or shrub (winter host). The eggs hatch on this plant in the spring and the aphids have several generations on this plant. Later, all winged forms are produced and they leave the winter host and move on to feed on a different type of plant (summer host). Summer hosts for these plants include various garden plants and weeds. Some of the more common aphids that have alternating hosts in Colorado are listed in Table 2.
Table 2: Some common Colorado aphids that alternate between woody and herbaceous hosts.
Aphid Host Hibernation Summer host
Black cherry aphid Woolly elm aphid Wild mustards
Currant aphid Currant Wild mustards
Green peach aphid Peach, plum, apricot Peppers, cabbage, potatoes, many garden plants
Leafcurl plum aphid Plum Various aster-plants of the family,
clover, vinca, thistle