Centaurea
Guides
Bangasternus
Bangasternus is a genus of true weevils (Curculionidae) comprising small, dark-colored species used as biological control agents against invasive knapweeds and starthistles (Centaurea spp.). Adults are typically 4 millimeters long, dark gray, and hairy. The genus is notable for its host specificity to Centaurea species, with larvae developing within flower heads where they consume developing seeds. Several species have been introduced to North America for biocontrol purposes, including B. fausti and B. orientalis.
Chaetorellia
Chaetorellia is a genus of tephritid fruit flies (family Tephritidae) containing approximately 11 described species. Species in this genus are specialists on Asteraceae flower heads, with larvae developing within capitula and feeding on developing florets and seeds. Several species have been investigated or deployed as biological control agents against invasive thistles and knapweeds, particularly yellow starthistle (Centaurea solstitialis). The genus is characterized by distinctive morphological features and host-specificity patterns that have been taxonomically revised.
Chaetorellia australis
yellow starthistle peacock fly
Chaetorellia australis is a tephritid fruit fly native to southern Europe and the Mediterranean, introduced to the western United States in 1988 as a biological control agent for the invasive weed yellow starthistle (Centaurea solstitialis). Adult females deposit eggs beneath bracts on host flower heads, and larvae tunnel into developing seeds, destroying up to 90% of seeds within an infested capitulum. The species exhibits a host-marking pheromone behavior that prevents multiple oviposition events in the same flower head and facilitates male aggregation. Despite significant seed destruction at the individual capitulum level, field populations generally remain low and have had limited impact on overall starthistle seed production.
Cyphocleonus achates
knapweed root weevil
Cyphocleonus achates is a Eurasian root-feeding weevil introduced to North America as a classical biological control agent against invasive knapweeds, particularly spotted knapweed (Centaurea maculosa) and diffuse knapweed (C. diffusa). Adults are flightless, large-bodied weevils that feed on foliage, while larvae cause significant damage by mining into root cortex and inducing gall formation. The species has established populations across much of the western United States and is considered one of the most damaging root-feeding insects on knapweed in its native range.
Larinus minutus
lesser knapweed flower weevil
Larinus minutus is a small true weevil used as a biological control agent against invasive knapweeds, particularly diffuse knapweed (Centaurea diffusa) and spotted knapweed (Centaurea maculosa). Native to southern Europe and the Mediterranean, it was first released in the United States in 1991 and is now established throughout the western United States. Adults feed on knapweed foliage and flowers, while larvae develop within flower heads and consume developing seeds, often destroying 100% of seeds in infested heads.