Trichosirocalus horridus
Introduction '''''Trichosirocalus horridus''''' is a species of true weevil, native to Europe. It is a biological pest control agent that was introduced into the United States in 1974 to control exotic thistles, especially in the ''Cirsium'' and ''Carduus'' genera.
Life history ''T. horridus'' feeds on the rosettes of thistles, with the larvae causing most damage to the plant.
Nontarget impacts In 2004, ''T. horridus'' was observed feeding on the native thistle ''Cirsium altissimum'' L. in Nebraska. The weevil was observed on the native thistle at about the same rate as the targeted invasive thistle (''Cirsium vulgare''). ''T. horridus'' has also been observed feeding on 5 native ''Cirsium'' species in Tennessee.
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