Brachycaudus cardui

Linnaeus, 1758

thistle aphid, plum-thistle aphid

Brachycaudus cardui is a heteroecious with a complex alternating between primary woody (Prunus spp.) and secondary herbaceous hosts, primarily thistles and other Asteraceae. Wingless females are small (1.8–2.5 mm), oval to pear-shaped, and variable in color. The species is notable for causing leaf roll on Prunus and for transmitting plum pox virus, a serious agricultural . Colony establishment depends heavily on attendance.

Brachycaudus cardui by no rights reserved, uploaded by Jesse Rorabaugh. Used under a CC0 license.

Pronunciation

How to pronounce Brachycaudus cardui: //ˌbræ.kɪˈkaʊ.dəs ˈkɑːr.dju.aɪ//

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

Identification

The dark, shining patch on the distinguishes B. cardui from the similar plum leaf curl (Brachycaudus helichrysi). The combination of heteroecious (Prunus to Asteraceae alternation), small size, and color variability further supports identification. Microscopic examination may be required for definitive separation from .

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Habitat

Found in diverse environments including orchards, meadows, roadsides, and damp areas. Primary are cultivated and wild Prunus trees. Secondary hosts include thistles (Carduus, Cirsium), other Asteraceae, and occasionally Boraginaceae. Colonies require attendance for successful establishment; ant exclusion causes colony failure even on suitable host plants.

Distribution

Widely distributed across Europe, Asia, North Africa, and North America. Documented in Hungary on Senecio jacobaea in northwestern regions, and present on the Azores (Faial, Flores, São Miguel, Terceira) and in Belgium.

Seasonality

Active on primary Prunus in spring and autumn. Migrates to secondary herbaceous hosts (Asteraceae, Boraginaceae) during summer months. Winged individuals return to primary hosts in autumn to complete the seasonal cycle.

Diet

Phloem-feeding with -alternating strategy: primary hosts are Prunus (plum, cherry, apricot, peach, damson); secondary hosts include thistles (Carduus, Cirsium), other Asteraceae such as ragwort (Jacobaea vulgaris), and occasionally Boraginaceae such as Symphytum.

Host Associations

Prunus domestica - primary plum
Prunus avium - primary cherry
Prunus armeniaca - primary apricot
Prunus persica - primary peach
Prunus insititia - primary damson
Carduus - secondary thistle
Cirsium - secondary thistle
Jacobaea vulgaris - secondary ragwort; colonies fail without attendance
Senecio jacobaea - secondary documented in Hungary
Symphytum - secondary Boraginaceae; occasionally used

Life Cycle

Heteroecious with obligatory alternation. Overwinters as on primary Prunus hosts. Spring reproduce viviparously on Prunus, producing winged migrants that disperse to secondary herbaceous hosts in early summer. Multiple parthenogenetic generations occur on secondary hosts. Winged individuals return to Prunus in autumn to produce sexual morphs and eggs. Colony persistence on secondary hosts depends on attendance.

Behavior

Forms colonies attended by ants that feed on honeydew and defend against . Experimental exclusion of ants causes colony failure even when plants are abundant. Winged migrants exhibit directed between primary and secondary hosts. On secondary hosts, colonies are typically found on stems and flowerheads.

Ecological Role

Herbivore that induces leaf rolling on primary . Serves as honeydew producer supporting mutualists. Acts as of plum pox virus (Sharka ), transmitting this serious among Prunus with significant agricultural consequences.

Human Relevance

Agricultural pest of stone fruit orchards. Direct damage includes leaf rolling on Prunus spp. Indirect damage through transmission of plum pox virus, which causes significant economic losses in plum, peach, apricot, and cherry production. attendance complicates efforts.

Similar Taxa

Brachycaudus helichrysiSimilar and also infests Prunus; distinguished by absence of dark shining patch on

More Details

Ant mutualism dependency

Research has demonstrated that B. cardui colonies fail to establish on secondary in the absence of ants, even when suitable host plants are abundant. This obligate or near-obligate mutualism involves ants feeding on honeydew and providing protection from and .