Bangasternus orientalis

Yellow starthistle bud weevil
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Family:	Curculionidae
Subfamily:	Molytinae
Tribe:	Rhinocyllini
Genus:	Bangasternus
Species:	B. orientalis
Binomial name
	Bangasternus orientalis; Capiomont, 1873

Last updated May 28, 2024

Bangasternus orientalis is a species of true weevil known as the yellow starthistle bud weevil. It is used as an agent of biological pest control against the noxious weed yellow starthistle (Centaurea solstitialis).

The adult weevil is brown with a thin coat of light mottled hairs. It is about 6 millimeters long. The female lays up to 470 eggs near the flower heads of yellow starthistle and glues them with a dark-colored mucilage. When the larva emerges from its egg, it tunnels up into the flower head, where it consumes the flower parts and developing seeds. It then constructs a sort of cocoon from the remnants of the flower and seed parts and pupates there. Most of the damage to the plant is done by the larva, which destroys 50-60% of the seeds in a given flower head. It is host-specific, attacking only yellow starthistle and sometimes purple starthistle (C. calcitrapa); it does not attack any native plants.

This weevil is native to southern Europe and the Mediterranean. It was first released as a biocontrol agent in the United States in 1985. It is now established throughout the western United States, wherever yellow starthistle is found. It helps prevent the spread of the weed, but it is not as common or effective as other yellow starthistle biocontrol agents.

The efficacy of Bangasternus orientalis Capiomont against its host Centaurea solstitialis L. was determined at two different sites (low and high elevation) in California over a 2-yr period. Host plant and weevil phenology were delayed at the high elevation site. Consequently, the initiation of secondary flower buds (high elevation site) was extended well into November, long after the ovipositing adult weevil population had expired. More than 50% of the egg-bearing test heads did not become infested with mature pupae because of larval mortality. After seed reduction by the weevil, 70% of the seeds remained in the test heads. Our data suggest that B. orientalis appears to be ineffective by itself as a biological control agent of yellow starthistle in California.

Life Cycle

Overwintering adults appear on plants in the spring through early summer. Eggs are laid on young leaves under developing flower heads. Larvae hatch, tunnel into the stem, and ultimately into the flower head, where they feed on young seeds. Pupation occurs within the seed heads. New adults then exit the plant to overwinter.

Habitat

Spotted and diffuse knapweed are weed species that can be found throughout the northern tier of states and as far south as Nebraska and Virginia. These highly competitive weed species favor and establish quickly on disturbed sites and overgrazed rangeland. Both weeds will invade well established grassland communities and out compete the native vegetation. The release of B. fausti is part of a program to introduce a complex of spotted and diffuse knapweed enemies to help control these weeds.

Field Identification

Several insects have been released for control of yellow starthistle. B. orientalis can be distinguished from the other seed head beetles, Eustenopus villosus and Larinus curtus, by its much shorter and blunt snout. B. orientalis also has much shorter body hairs than E. villosus.

Pests Attacked

B. fausti is considered host specific and limited to a few species in the genus Centaurea, specifically C. diffusa (diffuse knapweed), C. maculosa (spotted knapweed), C. calcitrapa (purple star-thistle), C. squarrosa (squarrose knapweed), and will rarely attack C. solstitialis (yellow star- thistle), all of which are introduced weeds. Extensive host specificity tests were conducted in the field and laboratory in Europe before B. fausti was cleared and released in the United States.^[1]

Availability

This beetle is readily available wherever yellow starthistle is found. Adults can be collected from spring through early summer. However, because its impacts are usually secondary relative to E. villosus, and because it is likely already present at most starthistle sites, redistribution may be unnecessary.^[2]

Related Research Articles

Centaurea is a genus of over 700 species of herbaceous thistle-like flowering plants in the family Asteraceae. Members of the genus are found only north of the equator, mostly in the Eastern Hemisphere; the Middle East and surrounding regions are particularly species-rich.

<i>Centaurea diffusa</i> Species of flowering plant

Centaurea diffusa, also known as diffuse knapweed, white knapweed or tumble knapweed, is a member of the genus Centaurea in the family Asteraceae. This species is common throughout western North America but is not actually native to the North American continent, but to the eastern Mediterranean.

Centaurea calcitrapa is a species of flowering plant known by several common names, including red star-thistle and purple star thistle. It is native to Europe but is rarely found there, it is known across the globe as an introduced species and often a noxious weed. The species name calcitrapa comes from the word caltrop, a type of weapon covered in sharp spikes.

Centaurea solstitialis, the yellow star-thistle, is a species of thorny plant in the genus Centaurea, which is part of the family Asteraceae. A winter annual, it is native to the Mediterranean Basin region and invasive in many other places. It is also known as golden starthistle, yellow cockspur and St. Barnaby's thistle.

Bangasternus fausti is a species of true weevil known as the broad-nosed seed head weevil. It is used as an agent of biological pest control against noxious knapweeds, particularly spotted knapweed, squarrose knapweed, and diffuse knapweed.

Chaetorellia acrolophi is a species of tephritid fruit fly known as the knapweed peacock fly. It is used as an agent of biological pest control against noxious knapweeds, especially spotted knapweed.

Cyphocleonus achates is a species of true weevil known as the knapweed root weevil. It is native to southern Europe and the Mediterranean and is used as an agent of biological pest control against noxious knapweeds, especially spotted knapweed. It has recently been spotted in India.

Larinus minutus is a species of true weevil known as the lesser knapweed flower weevil. It is used as an agent of biological pest control against noxious knapweeds, especially diffuse knapweed and spotted knapweed.

Larinus obtusus is a species of true weevil known as the blunt knapweed flower weevil. It is used as an agent of biological pest control against noxious knapweeds, especially spotted knapweed.

Metzneria paucipunctella is a species of moth known as the spotted knapweed seed head moth. It is used as an agent of biological pest control against noxious knapweeds, particularly spotted knapweed.

Chaetorellia australis is a species of tephritid fruit fly known as the yellow starthistle peacock fly. It is used as an agent of biological pest control against the noxious weed yellow starthistle.

Eustenopus villosus is a species of true weevil known as the yellow starthistle hairy weevil. It is used as an agent of biological pest control against the noxious weed yellow starthistle.

Larinus curtus is a species of true weevil known as the yellow starthistle flower weevil. It is native to Southern Italy, Southern Europe, the Middle East and the Caucasuses. It is used as an agent of biological pest control against the noxious weed yellow starthistle in the United States.

Centaurea iberica, the Iberian knapweed or Iberian star-thistle, is a species of Centaurea. It is native to southeastern Europe and southwestern Asia. It is known elsewhere as an introduced species and a noxious weed.

Urophora affinis is a species of tephritid or fruit flies in the genus Urophora of the family Tephritidae. It has been released in the United States and Canada as a biocontrol agent to control spotted knapweed. U. affinis became established in Montana in 1973.

Puccinia jaceae var. solstitialis is a species of fungus in the Pucciniaceae family. It is a plant pathogen that causes rust. Native to Eurasia, it is the first fungal pathogen approved in the United States as a biological control agent to curb the growth of the invasive weed yellow starthistle.

Larinus filiformis is a species of true weevil found in Armenia, Azerbaijan, Turkey, and Bulgaria.

Chaetorellia succinea is a species of tephritid fruit fly that was accidentally released in 1991 into the United States and had since become one of the major biological pest controls against the noxious weed yellow starthistle.

Centaurea stoebe, the spotted knapweed or panicled knapweed, is a species of Centaurea native to eastern Europe, although it has spread to North America, where it is considered an invasive species. It forms a tumbleweed, helping to increase the species' reach, and the seeds are also enabled by a feathery pappus.

Meadow knapweed, also known as hybrid knapweed or protean knapweed, is a fertile hybrid between black knapweed and brown knapweed. The taxonomic status of the species is uncertain, and meadow knapweed has been variously described as different species.

References

Coombs, E. M., et al., Eds. (2004). Biological Control of Invasive Plants in the United States. Corvallis: Oregon State University Press, 423.

External links

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[1] "Bangasternus fausti".

[2] "Bangasternusorientalis".

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