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Bagworms

  • Bagworms are caterpillars (larvae of moths) that live inside a spindle-shaped bag.
  • The bag, 1-2 inches long, is made of unbelievably tough silk and bits of leaves and twigs from the host plant.
  • The bag may become 2 inches long and are dragged with them wherever they go, like mobile homes.

Life Cycle

  • The eggs overwinter in the bag and hatch in late spring.
  • As they hatch, they crawl out of the bottom of the bag and spin down on a strand of silk.
  • The larvae on a string are often picked up by wind and ballooned to nearby plants.
  • When a suitable host is found, the young larvae immediately begin to feed and construct their bags or homes.
  • As the caterpillars grow, the bag enlarges.
  • Full grown larvae are 3/4 - 1 inch long, dark brown with white to yellow heads and a spotted thorax.
  • After pupation (late summer), the males emerge as black moths with furry bodies, feathered antennae, and clear wings with a span of almost 1 inch.
  • The female is a wingless moth that never leaves the bag.
  • She is fertilized by the male, lays 500-1,000 eggs inside the bag and dies.
  • There is one generation a year.

Control

  • Bagworms are difficult to control because they may go unnoticed.
  • There are few known parasites and predators and they are protected by their bags.
  • Light infestations may be cut off and the bags destroyed.
  • Timing of the chemical applications is critical. 
  • Applications should be made while the larvae are young, during mid to late June.
  • The mature larvae are not easily killed.