Sugarbeet Root Aphid
by Kevin Floate, Hector Carcamo, Tyler Wist
Like many aphids, the sugarbeet root aphid (Pemphigus betae) has a complex life cycle on two host plants. It overwinters as an egg on the primary host, which is typically narrowleaf cottonwood (Populus angustifolia) or balsam poplar (Populus balsamifera). The aphid that hatches from the egg is called the aphid stem mother. In spring, it begins to feed on still-expanding leaves causing the formation of a hollow structure on the leaf blade (the leaf gall). Inside the gall, the stem mother gives live birth to several generations of genetically identical female offspring with as many as 300 individuals per gall. In mid-summer, some of these females develop wings, exit the gall, and disperse to colonize the roots of herbaceous secondary hosts.
Secondary hosts include plants in Family Amaranthaceae (sugar beet, quinoa, lamb’s quarters, pigweed, spinach, Swiss chard, dock) plus some species of plants in Family Asteraceae (e.g., lettuce). Colonizing aphids give live birth to several generations of offspring that continue to feed on the roots of the secondary host.
In late summer, they produce a generation with both male and female winged individuals. The sexes mate and mated females return to the primary host to lay a single overwintering egg on the bark of the tree.
Click here for more details of the lifecycle of this and other gall-forming aphids on cottonwood trees are available online
Control of this pest on secondary hosts with insecticides is not effective because the aphids are feeding underground on the roots. A better approach is early seeding, good soil fertility and irrigation help to mitigate damage. Furthermore, chloropid flies are important predators that can reduce aphid abundance in the soil.
Reference: Cranshaw, W., Kondratieff , B.C. and Qian, T. 1990. Insects associated with Quinoa, Chenopodium quinoa, in Colorado. Journal of the Kansas Entomological Society 63: 195-199. [reports the closely-related species Pemphigus populivenae on quinoa.] P. betae and P. populivenae co-occur on primary hosts and often on secondary hosts.