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Urophora cardui or the Canada thistle gall fly is a fruit fly which, contrary to its common name, is indigenous to Central Europe
Widespread and common
Habitat, Grasslands, Hedgerows and meadows containing Creeping Thistle/ Canada Thistle
Flying time. It flies from May to September/October.
Any number of eggs are laid from just one to as many as thirty, which are laid on the stems of the Canada thistle. (Cirsium arvense) during the host's growing season. After hatching, the larvae burrow into the stem of the plant and form a gall (or swelling). . All the plants nutrients concentrate in the gall and do not go to other places of the plant. The host plant is then too weak to fight off other dangers and the growth is stunted, as the stem is usually too deformed to reproduce seeds. Therefore, thistle reproduction is stopped or slowed, but Urophora Cardui does not normally completely kill the plant. During maturing, the larva will be 98% of its full body weight, and appear as an adult. The larvae pupate in early spring for between 24 to 35 days, and appear reddish brown and remain inside the gall. The fly goes through a tunnel formed in the gall during May to October.
The Canada thistle gall fly has been introduced to North America from Europe to control the population of its host plant, Canada, or creeping thistle; which is an invasive introduced wildflower in North America.
Urophora cardui has been approved by the Animal and Plant Health Inspection service. Study shows that a combined effort of insects, including the Urophora cardui, has reduced thistle by as much as 48%. The insect is not a threat to non-target species, and the return of grasses and forbs has been seen in previously infested areas.
Read MoreWidespread and common
Habitat, Grasslands, Hedgerows and meadows containing Creeping Thistle/ Canada Thistle
Flying time. It flies from May to September/October.
Any number of eggs are laid from just one to as many as thirty, which are laid on the stems of the Canada thistle. (Cirsium arvense) during the host's growing season. After hatching, the larvae burrow into the stem of the plant and form a gall (or swelling). . All the plants nutrients concentrate in the gall and do not go to other places of the plant. The host plant is then too weak to fight off other dangers and the growth is stunted, as the stem is usually too deformed to reproduce seeds. Therefore, thistle reproduction is stopped or slowed, but Urophora Cardui does not normally completely kill the plant. During maturing, the larva will be 98% of its full body weight, and appear as an adult. The larvae pupate in early spring for between 24 to 35 days, and appear reddish brown and remain inside the gall. The fly goes through a tunnel formed in the gall during May to October.
The Canada thistle gall fly has been introduced to North America from Europe to control the population of its host plant, Canada, or creeping thistle; which is an invasive introduced wildflower in North America.
Urophora cardui has been approved by the Animal and Plant Health Inspection service. Study shows that a combined effort of insects, including the Urophora cardui, has reduced thistle by as much as 48%. The insect is not a threat to non-target species, and the return of grasses and forbs has been seen in previously infested areas.
