Species Trichosirocalus horridus - Thistle Crown Weevil

Musk Thistle Rosette Weevil, Musk Thistle Weevil, Rosette Weevil

Trichosirocalus horridus (Panzer)

Orig. Comb: Curculio horridus Panzer 1801

3-5 mm

Body densely covered with brownish scales, which form no definite pattern. Additionally, dorsal surface with numerous stiff, erect setae.

native to Europe, introduced in NA for thistle control (map)(1)

feeds on the rosettes of thistles (Carduus & Cirsium spp., Asteraceae)(1)

Female lays 500-800 eggs in clusters of 2 or 3 on the underside of leaves. Eggs hatch in 10-12 days. Larvae develop in basal portion of stem and root crowns. Complete development in 6-8 wks. Full grown larvae pupate in the soil in pupation chambers. Adults emerge in 12-20 days in the spring. They hide until the fall when they begin to feed. They overwinter as adults, eggs and larvae.

T. horridus was imported from Italy in 1970-1972 for testing and approved for field release in the USA in 1974. It first became established in VA and has since been relocated to many other states.(1) It is a very effective biocontrol of invasive musk and plume thistles. Unfortunately, it also feeds on some native thistles.

Cornell U.

Environ. Entomol. Occurrence of Trichosirocalus horridus (Coleoptera: Curculionidae) on native Cirsium altissimum versus exotic C. vulgare in North American tallgrass prairie.