Synonyms and other taxonomic changes
Agapeta zoegana (Linnaeus, 1767)
Phalaena (Tortrix) zoegana Linnaeus, 1767
Adult - small bright yellow moth, 10 mm in length, with brown wing bands. The adults may be found resting vertically on the knapweed stems or under the leaves. They have the appearance of dead or dying knapweed leaves. (2)
First released in the United States in 1984 and is now established in most western states. (3)
Type location: Europe.
Larvae feed on the roots of spotted knapweed primarily, diffuse and squarrose knapweeds secondarily. (3)
Adult moths emerge from knapweed roots in early July through early September. Mating takes place within twenty-four hours after emergence and the mated female begins laying eggs the next day. The eggs are laid in the stem crevices and on the leaves of the spotted and diffuse knapweed plants. The larvae hatch from the eggs in seven to ten days and move immediately to the root crown and mine into the root. Larvae are capable of killing small rosettes and then moving a few centimeters to another knapweed plant to feed. The larvae pupate in the root in midsummer. Adults live from eleven to fourteen days with each female laying from twenty-one to seventy-eight eggs in her lifetime. The moths are strong fliers and will invade new knapweed patches.