Rootworm Identification Guide
Learn how to recognize rootworm beetles and their larvae by color, shape, and where they turn up in the garden or field.
Read the full Rootworm encyclopedia entry →
Key Visual Features
Rootworm is the common name for the larval stage of several small beetles in the genus Diabrotica, though the term is often used loosely for both the larva and the adult beetle stage.
- Larvae: slender, worm-like, white to cream colored, about 1/3 to 1/2 inch long when mature, with a brown head capsule and a small brown plate on the tail end.
- Adult beetles: roughly 1/4 inch long, oval and somewhat flattened, with color patterns that vary by species — solid yellow-green, yellow with black stripes, or yellow with scattered black spots.
- Antennae: long and thread-like, often nearly as long as the body.
- Wings: adults have hardened forewings (elytra) that cover a functional pair of flight wings, and they are capable fliers.
- Legs: six slender legs typical of beetles, used for climbing on foliage and silks.
Where and When You'd See It
- Larvae live underground, feeding on roots, so they are rarely seen unless soil is dug up around plant roots.
- Adult beetles are the visible stage, commonly spotted on leaves, flowers, and silks of corn and other garden plants.
- Most active from mid to late summer, coinciding with flowering of host plants.
- Found in agricultural fields, home gardens, and areas with grassy or cultivated soil.
Similar-Looking Bugs
- Cucumber beetles: closely related and nearly identical in shape, often confused since striped and spotted forms overlap in appearance with rootworm beetles.
- Flea beetles: much smaller and rounder, with enlarged hind legs for jumping, unlike the more elongated rootworm beetle.
- Ladybird beetles: more domed and rounded in profile, lacking the flatter, elongated oval shape of rootworm beetles.
Quick ID Checklist
- Small oval beetle, about 1/4 inch, yellow-green base color
- Pattern of stripes or spots depending on species
- Long thread-like antennae nearly body length
- Larvae are white, slender, worm-like, found at root level
- Seen on leaves and flowers in mid to late summer
Frequently asked questions
How can I tell a rootworm beetle from a cucumber beetle?
They look extremely similar in shape and size; the main clue is the exact pattern of stripes or spots and the host plant it is found on, since the groups overlap heavily in appearance.
Are rootworm larvae ever seen above ground?
Rarely — the larvae stay in the soil near roots and are usually only noticed if soil is disturbed or roots are examined closely.
What time of year are adult rootworm beetles most visible?
Adults are most commonly spotted from mid to late summer when host plants are flowering.
Do rootworm beetles fly?
Yes, adults have a functional pair of flight wings under their hardened forewings and move readily between plants.