''Cyphocleonus achates'' is a species of

true weevil True most commonly refers to truth, the state of being in congruence with fact or reality. True may also refer to: Places * True, West Virginia, an unincorporated community in the United States * True, Wisconsin, a town in the United States * T ...

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 Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...

against noxious

knapweeds ''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 reg ...

, especially

spotted knapweed ''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 in ...

(''Centaurea maculosa''). It has recently been spotted in India. Cyphocleonus achates

Life history

The adult weevil is dark gray and white speckled and 14 to 15 millimeters long. The female lays about 100 eggs during her 8- to 15-week adult lifespan. The eggs are deposited one by one in notches the female digs into the root crown of the knapweed. The

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

emerges from the egg and tunnels into the root cortex where it feeds on the plant tissue. Sometimes a

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

is produced in the feeding area. Adults feed on the leaves but it is the larva that does the most damage to the plant. Small plants can be killed by the larva's destruction of the root tissue. In their native range, most ''C. achates'' overwinter as 2nd

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...

s, though in the introduced range, the vast majority overwinter as 1st instars.

Biocontrol in North America

It was first released as a knapweed biocontrol in the 1980s in the United States. It is established in much of the western United States and there is evidence that it reduces knapweed biomass. ''C. achates'' is thought to be responsible for a recent (2000s) observed decline in spotted knapweed, but this decline may also be attributable to a recent severe drought. The weevil prefers spotted knapweed, but it is sometimes found on

diffuse knapweed ''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 ...

. It has not been shown to attack native flora. ''Cyphocleonus achates'' was released to the

Hiawatha National Forest Hiawatha National Forest is a National Forest in the Upper Peninsula of the state of Michigan in the United States. Commercial logging is conducted in some areas. The United States Forest Service administers this National Forest; it is physical ...

in Michigan's Upper Peninsula in summer 2009.

References

* Coombs, E. M., et al., Eds. (2004). ''Biological Control of Invasive Plants in the United States''. Corvallis: Oregon State University Press, 212. * Stejskal, R. (2005b): Interesting records of some weevil species of the subfamily Lixinae (Coleoptera: Curculionidae) in southern Moravia with notes on their bionomics (Zajímavé nálezy několika druhů nosatců podčeledi Lixinae (Coleoptera: Curculionidae) na jižní Moravě s poznámkami k jejich bionomii). - Klapalekiana, 41: 63–69. Praha.

External links

Cornell Biocontrol Profile
{{Taxonbar, from=Q5200232 Molytinae Biological pest control beetles Insects used for control of invasive plants