Corn Rootworms

Larva (Figure 1): Slender, white to cream body with brownish head capsule and brown anal plate at the posterior end, about ½ inch long when mature. Feeds on roots.

Figure 1. Larvae - corn rootworm tunneling into root (P. Beauzay, NDSU)

Adults:

Northern corn rootworm (Figure 2): ¼ inch long, tan to pale green beetles.

Western corn rootworm: 3/16 to 5/16 inch long. Yellow to yellowish-green beetles with black markings on forewing. Most females (Figure 3) have three longitudinal black stripes on their forewings, and most males (Figure 4) have a nearly solid black marking.

Figure 2. Adult - northern corn rootworm (V. Calles-Torrez, NDSU)

Figure 3. Adult female - western corn rootworm (J. Knodel, NDSU)

Figure 4. Adult male - western corn rootworm (P. Beauzay, NDSU)

Cutworm

Larva (Figure 5): Black to pale gray, cylindrical-shaped body with markings (spots or stripes), about 1½ to 2 inches long when mature. Cut young plants below or above ground.

Adult (Figure 6): Dark brown, black, drab gray, dull yellow or tan moths with wing markings, robust body, wingspan length of 1¼ to 1½ inches.

Figure 5. Larva - black cutworm and feeding injury to corn (J. Kalisch, University of Nebraska)

Figure 6. Black cutworm moth (J. Kalisch, University of Nebraska)

European Corn Borer

Larva (Figure 7): Pinkish gray or pale brown body marked with small brown dots in rows, brown head, about ¾ to 1 inch long when mature. Defoliate leaves and tunnel into stalks and corn ears/shanks.

Adult (Figure 8): Straw-colored (pale yellow-brown) with brown wavy bands on wings, and 1 inch wingspread.

Figure 7: Larva - European corn borer in corn ear (V. Calles-Torrez, NDSU)

Figure 8. European corn borer moth (J. Knodel, NDSU)

Grasshopper

Nymph (Figure 9): Resembles the adults, but smaller without fully developed wings (wing pads only).

Adult (Figure 10): About 1¾ inches long, brown to grayish green, prominent head, large compound eyes, enlarged hind legs for jumping. Fully developed wings.

Grasshoppers feed on leaves, silks and ear tips.

Figure 9. Nymph - grasshopper (P. Beauzay, NDSU)

Figure 10. Adult - red-legged grasshopper feeding in corn ears (J. Knodel, NDSU)

Corn Aphid (Figure 11)

Nymph: Similar to adult but smaller, always without wings.

Adults: Small about 1/8 inch long, pear-shaped, pale to dark green, two cornicles (look like tail-pipes) at posterior end, winged or wingless.

Both nymphs and adults feed on plant juices.

Figure 11. Corn aphids and bird cherry-oat aphids, nymphs and adults (V. Calles-Torrez, NDSU)

Seed Corn Maggot

Larva (Figure 12): Maggotlike, about ¼ inch long, cylindrical, legless, pale yellow-white and sharply pointed at the head end with small black mouth hooks. Burrow into seeds, emerging stems and cotyledon leaves.

Adult (Figure 13): Grayish brown fly about ¼ inch long.

Figure 12. Larva - seed corn maggot (W. Cranshaw, Colorado State University, Bugwood.org)

Figure 13. Adult - seed corn maggot (Pest and Diseases Image Library, Bugwood.org)

Spider Mite

Immature: Similar to adult, but smaller with six to eight legs.

Adult (Figure 14): Very small, less than 0.02 inch (magnification is needed to see them in detail), green, yellow or orange body, two dark spots on the abdomen for two-spotted spider mite, eight legs. Located on the underside of leaves. Produce spiderlike webbing (Figure 15) and stippling injury on leaves (Figure 16).

Figure 14. Two-spotted spider mites (P. Beauzay, NDSU)

Figure 15. Webbing from two-spotted spider mites (D. Cappaert, Michigan State University, Bugwood.org)

Figure 16. Stippling injury from spider mites (nymphs and adults) on corn leaf (P. Beauzay, NDSU)

White Grub/June Beetle

Larva (white grub, Figure 17): White to cream body with brown head, three pairs of legs, C-shaped, about 1½ inches long when mature. Feeds on roots in soil.

Adult (Figure 18): Brown to reddish-brown beetles, about ¾ inch long.

Figure 17. White grub (S. Katovick, Bugwood.org)

Figure 18. June beetle (S. Katovick, Bugwood.org)

Published with supported from the North Dakota Corn Council and the USDA National Institute of Food and Agriculture, Hatch Project Accession No. 1024297 and the Crop Protection and Pest Management Program [grant no. 2017-70006-27144].