Mission Statement of the Nebraska Crop Surveillance Network:
Mitigate the impact of crop diseases and insect pests and safeguard Nebraska's agriculture against threats of bioterrorism.

Insect: Imported Long Horned Weevil

Taxonomy:

Common Name: Imported Long-horned Weevil
Scientific Name: Calomycterus setarius

Distribution:

  • Introduced from Asia.

  • First recorded in the U.S. in New York (1929).

  • Spread west reaching Iowa by the 1940s.

  • Currently, the western edge of its range is eastern Nebraska.

Identification:

  • A stout beetle, about 3/16 inches long.

  • Mottled gray in color.

  • The antennae are half the length of the body and elbowed near the middle.

Imported Longhorned Weevil

Imported longhorned weevil on young soybean plants

Imported longhorned weevils

Life Cycle:

  • All adults are female and reproduce without males.

  • In spring, eggs are laid in the soil in weedy and grassy areas, hatching in 8-12 days.

  • The white, grub-like larvae feed on the roots of a variety of plants, and then pupate in early June.

  • Adults begin emerging in grassy areas or pastures during mid-June and begin feeding.

  • There is one generation per year.

  • Adults do not have wings.

Host Range:

  • Larvae feed on the roots of aster, clover, and turf grass.

  • Adults feed on the foliage of a variety of plants, including soybean.

Injury and Damage:

  • Adults injure soybean by feeding on leaf tissue and smaller veins.

  • Economic damage is more likely to occur when large numbers of weevils move from grassy and weedy areas into late-planted soybeans, where plants are small.

  • Under heavy infestation, over a dozen weevils per seedling are common.

  • Because the weevils are flightless, they primarily are pests along field edges that are next to grassy or weedy areas. The exception is the first year out of CRP or pasture.

  • In this case, infestation can occur throughout the soybean field.

Defoliation by the imported long-horned weevil

Monitoring:

  • Scout from mid-June through early July when the adults are emerging.

  • Focus on the field edge next to grass or weeds.

  • If the field was grass or pasture during the past year, scout throughout the field.

Management:

  • If treatment is warranted along the field edge, make sure to provide a wide buffer between damaged and undamaged foliage.

Notes: