''Psylliodes chrysocephala'' or ''Psylliodes chrysocephalus'', commonly known as the cabbage-stem flea beetle, is a species of

leaf beetle The beetle family Chrysomelidae, commonly known as leaf beetles, includes over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making it one of the largest and most commonly encountered of all beetle families. Numerous s ...

situated in the subfamily

Galerucinae The Galerucinae are a large subfamily of the leaf beetles (Chrysomelidae), containing about 15,000 species in more than 1000 genera, of which about 500 genera and about 8000 species make up the flea beetle tribe Alticini. The division into tr ...

and the tribe

Alticini The flea beetle is any small, jumping beetle of the leaf beetle family (Chrysomelidae) that is part of the tribe Alticini, which is part of the subfamily Galerucinae. Historically the flea beetles were classified as their own subfamily. Tradi ...

(flea beetles).

Description

''P. chrysocephala'' measures 3.0–4.0 mm in length. It is variably coloured, but most often a dark metallic blue. Like all flea beetles it has large hind femora which it can use to jump. These are orange-red in colour with the hind femora darkened. It is differentiated from other members of the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

through a lack of anterior angles on its

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...

, the punctures on top of the head being as coarse as those on the

elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...

, and its first front tarsal segment being equal in length to its third. Psylliodes chrysocephala larva (31827378971).jpg, ''Psylliodes chrysocephala'' larva feeding in stem of ''

Brassica napus Rapeseed (''Brassica napus'' subsp. ''napus''), also known as rape and oilseed rape and canola, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed, which naturall ...

'' Psylliodes chrysocephala (31906272736).jpg, ''P. chrysocephala'' pupa Cabbage-stem Flea Beetle (37130910672).jpg, Adult beetle

Distribution

It is native to the Western

Palaearctic The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa. Th ...

, including Macaronesia, Cape Verde and North Africa and has been introduced into Canada.

Lifecycle

Adult beetles mate in late August on the leaves of host plants, with eggs first laid 5–10 days after copulation. Oviposition takes place from the end of September through winter until mid-April and a single female may lay up to 1000 eggs, deposited in small clusters in the soil beneath the host plant at depths of 1–5 cm. Larvae hatch after about 60 days and feed within the stem and leaves of the host plant. Fully developed larvae emerge in early summer and pupate in the soil. Newly emerged adults appear from May each year. Adults may enter an

aestivation Aestivation ( (summer); also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a lowered m ...

period over Summer after the harvest of mature rape plants. After mating in late summer, some adults will overwinter.

Behaviour and habitat

''P. crysocephala'' can be found in various habitats, depending on the availability of a host plant. It is particularly associated with wild and cultivated members of the plant family

Brassicaceae Brassicaceae () or (the older but equally valid) Cruciferae () is a medium-sized and economically important Family (biology), family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous pla ...

. It has been directly associated with ''

'', '' B. nigra'' (black mustard), '' B. oleracea'' (cabbages, cauliflowers), '' B. rapa'' (turnip rape), ''

Nasturtium officinale Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic flowering plant in the cabbage family, Brassicaceae. Watercress is a rapidly growing perennial plant native to Eurasia. It is one of the oldest known leaf vegetab ...

'' (watercress), ''

Raphanus sativus The radish (''Raphanus sativus'') is a flowering plant in the mustard family, Brassicaceae. Its large taproot is commonly used as a root vegetable, although the entire plant is edible and its leaf, leaves are sometimes used as a leaf vegetable. O ...

'' (radish), ''

Sinapis alba White mustard (''Sinapis alba''), also called yellow mustard, is an annual plant of the cabbage family. It is sometimes also referred to as ''Brassica alba'' or ''B. hirta''. It probably originated in the Mediterranean region, but is now ...

'' (white mustard), '' S. arvensis'' (wild mustard), and '' Tropaeolum majus'' (common nasturtium).

As an arable pest

It is a serious pest of rape in northern Europe. In central parts of Europe it has a cyclic appearance with peaks in populations at intervals of about seven years. In the UK, it is the most important establishment pest of rape, leading to yield losses of up to 20%.

Pest control

The management of ''P. chrysocephala'' has become increasingly difficult due to the ban on neonicotinoids and the rise of pyrethroid-resistant populations. RNA interference (RNAi) has emerged as a promising alternative for pest control due to its species-specific and environmentally friendly nature. Recent research has demonstrated that orally delivered double-stranded RNA (dsRNA) can effectively silence essential genes in ''P. chrysocephala'', leading to significant mortality. A study tested 27 dsRNAs targeting genes identified in a genome-wide RNAi screen in ''Tribolium castaneum'' and found four highly effective target genes that caused 100% mortality within 8–13 days. These genes, primarily encoding proteasome subunits, showed strong dose-dependent effects with LD50 values as low as ~20 ng. Additionally, effective dsRNAs reduced feeding damage by up to 75% and affected beetle locomotion. Off-target prediction analysis was performed to design environmentally safe dsRNAs that minimize risks to non-target organisms, such as pollinators. These findings highlight the potential of RNAi-based insecticides as an innovative and sustainable pest management strategy against ''P. chrysocephala''.

References

External links

High resolution images of ''Psylliodes crysocephala''
{{Taxonbar, from=Q586373 Agricultural pest insects Beetles of Europe Taxa named by Carl Linnaeus Alticini Beetles of North America Beetles described in 1758