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.

Insects: Painted Lady (thistle) Caterpillar

Taxonomy:

Common Name: Painted Lady Butterfly
Scientific Name: Vanessa cardui

Distribution:

  • Found worldwide.

Importance:

  • Occasional pest.

Identification:

  • Adults are called the painted lady butterfly.

  • Caterpillars easily recognized by their multi-branched spines.

  • Mature larvae are about 1-¼ inches (32 mm) in length.

  • They are brown to black with yellow striping along each side of the body.

  • Larvae are found in webbed leaves where they feed.

Thistle caterpillar, lateral view

Life Cycle:

  • Over winter in tropical and subtropical areas.

  • Adults migrate northward in the spring.

  • Upon arrival, females lay pale green, barrel-shaped eggs singly on the tops of host plant leaves.

  • The caterpillars feed for 2 to 4 weeks, and then pupate.

  • The butterfly emerges from the chrysalis in 7 to 10 days.

  • Multiple generations can occur each summer.

Host Range:

  • Caterpillars feed on over 100 species of plants.

  • The most common plants are Canada thistle, sunflower, soybean, and vegetable plants.

Injury & Damage:

  • Individual caterpillars bind 3 - 4 leaflets together with webbing, usually in the upper canopy of the plant.

  • They live within the webbing, feeding on the leaflets, and depositing numerous black fecal droppings.

  • Inside the webbing, caterpillars consume approximately 40 square inches of soybean leaves, causing 97 percent of the leaf removal during the last two larval stages (when larvae are 3/4 to 1 ¼ inches in length).

  • Most often a problem on V3-V4 soybeans.

Monitoring:

  • Visual counts

Management:

  • Various insecticides are labeled for management.

  • In vegetative (pre-flowering) stages consider treatment if the insects are present and feeding and defoliation will reach 40%.

  • In pod-forming or pod-filling stages consider treatment if the insects are present and defoliation will reach 20%.

  • These percentages can vary 5% to 10% according to the stage or type of insect(s) present, environmental conditions, the specific stage of the soybean, and the size and condition of the canopy.

Notes: