On this page
How to identify it
- Wingless aphids on the roots are pinhead-sized and pale yellowish to white-yellow.[1][2]
- They secrete dull white wax that gives roots a mealy look and can be mistaken for mold.[1][2]
- Winged aphids are sometimes seen in woolly wax masses at the crown as they crawl up from the roots to fly to new hosts.[1]
- UC IPM finds it mostly on the fibrous roots rather than the main storage root, while the PNW handbook describes it colonizing the taproot.[1][2]
Look-alikes
Where it lives
In California it is more common in the Central Valley than in the Imperial Valley; it is also a pest of sugar beets in the Pacific Northwest and has been studied in western Nebraska and Utah.[1][2][5][3]
Biology and life cycle
It typically alternates each year between two kinds of hosts: cottonwood trees, where it forms galls on the leaves, and herbaceous plants, where it lives on the roots.[3]
On narrow-leaf cottonwood the aphid makes a leaf fold gall that surrounds it, and inside the gall it feeds on the contents of the leaf's phloem.[4]
Not every aphid line makes the trip to cottonwood. In a Utah population, some clones rarely produced the winged migrants that start the cottonwood phase and stayed on roots.[3]
Root hosts include sugarbeet, table beet, spinach and chard, and weeds such as lambsquarters and redroot pigweed.[1]
Infestations typically build up in late summer and are favored by dry soil and drought-stressed plants. The aphid is readily carried in irrigation water, and UC IPM advises cleaning equipment before it leaves an infested field.[2][1]
Damage and signs
- Severely infested plants turn yellowish and wilt easily, and with prolonged moisture stress the storage root becomes soft and rubbery. In the field, damage shows up as round or oval patches of wilted, collapsed or dying plants.[1]
- California studies show that even light to moderate infestations (under 10 percent) can cause serious yield losses.[1]
Health risk
It is a plant pest; none of the sources mention any risk to people or pets.[1][2]
Control
Prevention
Plant resistant varieties where they are available, and keep plants from drought stress with a proper irrigation schedule; UC IPM also advises keeping the gap between the last irrigation and harvest short.[2][1]
Rotate: do not plant sugarbeet, table beet, spinach or chard in an infested field for at least 3 years, and control weed hosts in every following crop.[1]
Sanitation
Work infested fields right after harvest and destroy any beets left behind, and destroy weed hosts such as lambsquarters and redroot pigweed, including along field margins.[1]
Clean equipment before moving from an infested field, and never irrigate a host crop with tailwater from an infested field, because the aphid travels in irrigation water.[1]
Biological control
Larvae of a predatory fly attack the aphid; the PNW handbook says this generally keeps infestations in check, while UC IPM doubts it, or a fungus disease that also infects the aphid, can control populations today. Avoid unnecessary insecticides.[2][1]
Pesticides
Chemical control is difficult because the aphids live hidden in the soil. Fields are usually infested in late summer, after at-plant treatments have lost effect; in Nebraska, a neonicotinoid seed treatment reduced root aphid numbers but not enough to count as adequate control, and no chemicals were registered for it in California when UC IPM last updated its guideline.[2][5][1]
Common questions
- What is the white moldy stuff on my beet roots?
- It may be sugarbeet root aphid: pale, pinhead-sized aphids that cover roots in white wax resembling mold.[2][1]
- Can I spray for root aphids in my garden beets?
- Sprays have trouble reaching aphids hidden in the soil. Rotating away from beets, spinach and chard, removing weed hosts and leftover beets, and avoiding drought stress are the main tools.[2][1]
- Does it live anywhere besides roots?
- Yes. It typically spends part of the year in leaf galls on cottonwood trees and part on the roots of herbaceous plants, though some lines tend to skip the cottonwood phase and stay on roots.[3][4]
Sources
- University of California Statewide IPM Program, “Sugarbeet Pest Management Guidelines: Sugarbeet Root Aphid (UC ANR Publication 3469).” ipm.ucanr.edu/agriculture/sugarbeet/sugarbeet-root-aphid/ (accessed 2026-11-09)
- Pacific Northwest Pest Management Handbooks (Oregon State University, Washington State University and University of Idaho Extension), “Sugar beet-Sugar beet root aphid (PNW Insect Management Handbook, agronomic crops).” pnwhandbooks.org/insect/agronomic/sugar-beet/sugar-beet-sugar-beet-root-aphid (accessed 2026-11-09)
- Society for the Study of Evolution (Evolution), “Moran NA. Phenotype fixation and genotypic diversity in the complex life cycle of the aphid Pemphigus betae. Evolution 45(4):957-970 (1991) (abstract).” doi.org/10.1111/j.1558-5646.1991.tb04363.x (accessed 2026-11-09)
- Springer (Protoplasma), “Richardson RA, Body M, Warmund MR, Schultz JC, Appel HM. Morphometric analysis of young petiole galls on the narrow-leaf cottonwood, Populus angustifolia, by the sugarbeet root aphid, Pemphigus betae. Protoplasma 254(1):203-216 (2017) (abstract).” doi.org/10.1007/s00709-015-0937-8 (accessed 2026-11-09)
- Entomological Society of America (Environmental Entomology), “Pretorius RJ, Hein GL, Blankenship EE, Purrington FF, Bradshaw JD. Response of Pemphigus betae and beneficial epigeal arthropod communities to sugarbeet plant density and seed-applied insecticide in western Nebraska. Environmental Entomology 46(1):107-117 (2017) (abstract).” doi.org/10.1093/ee/nvw157 (accessed 2026-11-09)
- iNaturalist, “Pemphigus betae taxon page (order and family).” www.inaturalist.org/taxa/453301 (accessed 2026-11-09)