Bangasternus orientalis

Capiomont, 1873

yellow starthistle bud weevil

Bangasternus orientalis is a small true weevil (Curculionidae) used as a agent against the weed yellow starthistle (Centaurea solstitialis). Native to southern Europe and the Mediterranean, it was introduced to the United States in 1985 and has become established throughout the western United States. feed on leaves and flower buds, while larvae develop within flower and consume developing seeds, destroying 50-60% of seeds in infested heads.

Pronunciation

How to pronounce Bangasternus orientalis: /bæŋ.ɡəˈstɜːrnəs ɔːr.iˈɛn.teɪ.lɪs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other yellow starthistle seed beetles (Eustenopus villosus and Larinus curtus) by its much shorter and blunt snout. Body hairs are shorter than those of E. villosus. The compact size and mottled brown coloration with short are also characteristic.

Appearance

are brown with a thin coat of light mottled hairs, approximately 6 millimeters in length. The body is covered with short, blunt hairs. The snout is notably shorter and blunter than that of related seed weevils.

Habitat

Associated with yellow starthistle (Centaurea solstitialis) ; found in grasslands, rangelands, disturbed sites, and areas where the weed grows. are found on bolting host plants in spring and early summer.

Distribution

Native to southern Europe and the Mediterranean region. Introduced to the United States in 1985; now established throughout the western United States wherever yellow starthistle occurs, including California and other western states.

Seasonality

appear on plants from mid-May through early summer. Adults of summer emerge from seed from late July to mid-September. Oviposition begins about one week after overwintered adults appear and continues for approximately 2.5 months.

Diet

feed on young leaves and flower buds of yellow starthistle. Larvae feed on developing seeds and flower parts within the flower , destroying 50-60% of seeds in infested heads.

Host Associations

Centaurea solstitialis - primary yellow starthistle; primary target for
Centaurea calcitrapa - secondary purple starthistle; occasionally attacked

Life Cycle

(one per year). overwinter and emerge in spring. are laid singly on or near young buds and covered with a protective cap of dark mucilage. Larvae mine into flower , feed on developing seeds, then construct a cocoon from flower and seed remnants and pupate within the flower head. New adults exit to overwinter.

Behavior

Females glue to plant tissue using dark-colored mucilage. Larvae tunnel into flower and develop concealed within. are host-specific and do not attack native plants. In its native range, high egg and larval mortality (up to 98.7% and 84% respectively) due to limits buildup; in the introduced range without natural enemies, populations can reach higher densities.

Ecological Role

Herbivore and agent that reduces seed production of yellow starthistle. Helps limit spread of this weed, though it is considered less effective than other biocontrol agents such as Eustenopus villosus. Contributes to integrated weed management programs but does not provide sufficient control alone.

Human Relevance

Used as a agent for yellow starthistle, a noxious weed in western North American rangelands and grasslands. First released in the United States in 1985. Redistribution is generally unnecessary as it is already present at most starthistle sites. can be collected from spring through early summer for monitoring purposes.

Similar Taxa

Eustenopus villosusAlso a yellow starthistle seed weevil; distinguished by longer, more pointed snout and longer body hairs. E. villosus is more common and effective as a biocontrol agent.
Larinus curtusAnother yellow starthistle seed ; B. orientalis has a much shorter and blunter snout.

More Details

Biocontrol efficacy

Considered less effective than Eustenopus villosus; its impacts are usually secondary. High mortality from natural enemies in its native range limits growth, but it can achieve higher densities in the introduced range.

Host specificity testing

Field and laboratory studies confirm restriction to Centaurea; ornamental and crop plants were not used as oviposition sites. Atrophied were found in females caged on safflower (Carthamus tinctorius) with no oviposition occurring.