Psylliodes chrysocephala

P. chrysocephala measures 3.0–4.0 mm in length. It is variably coloured, but most often a dark metallic blue.{{cite book |author1=Hubble, D. |date=2012 |title=Keys to the adults of seed and leaf beetles of Britain and Ireland |publisher=Field Studies Council |page=77}} 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.{{cite web |url=http://www.coleoptera.org.uk/species/psylliodes-chrysocephala |title=Psylliodes chrysocephala (Linnaeus, 1758) |publisher=UK Beetle Recording (Coleoptera.org_ |accessdate=16 February 2018}}

It is differentiated from other members of the genus through a lack of anterior angles on its pronotum, the punctures on top of the head being as coarse as those on the elytra, 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

Psylliodes chrysocephala (31906272736).jpg|P. chrysocephala pupa

Cabbage-stem Flea Beetle (37130910672).jpg|Adult beetle

It is native to the Western Palaearctic, including Macaronesia, Cape Verde and North Africa and has been introduced into Canada.

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 period over Summer after the harvest of mature rape plants. After mating in late summer, some adults will overwinter.{{cite journal |author1=Kig, V. |date=2003 |title=Data on the Biology of Cabbage Stem Flea Beetle, Psylliodes Crysocephalus (Linnaeus, 1758) (Coleoptera, Chrysomelidae, Alticinae) |journal=Communications in Agricultural and Applied Biological Sciences |volume=68 |issue=4 |pages=231–237

|url=https://www.researchgate.net/publication/8557322}}

File:Colza (Gros plan) Cl J Weber01 (23566547692).jpg

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. It has been directly associated with Brassica napus, B. nigra (black mustard), B. oleracea (cabbages, cauliflowers), B. rapa (turnip rape), Nasturtium officinale (watercress), Raphanus sativus (radish), Sinapis alba (white mustard), S. arvensis (wild mustard), and Tropaeolum majus (common nasturtium).{{cite web |url=https://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=45335 |title=Plantwise Technical Factsheet: cabbage stem flea beetle (Psylliodes chrysocephala) |publisher=Plantwise}}

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.{{cite book |author1=Alford, D. V. |author2=Nilsson, C. |author3=Ulber, B. |date=2008 |chapter=Insect Pests of Oilseed Rape Crops |editor1=Alford, D. V. |title=Biocontrol of Oilseed Rape Pests |publisher=Blackwell |pages=9–42}} In the UK, it is the most important establishment pest of rape, leading to yield losses of up to 20%.{{cite journal |author1=Lane, A. |author2= Cooper, D. A. |author3= Dale, M. f. B. |author4= Dewar, A. M |author5= Froud-Williams, R. J. |author6= Hocking, T. J. |author7=Jones, D. G. |author8=Rea, B. L. |date=1989 |title='Production and protection of oilseed rape and other Brassica crops': A meeting held in Cambridge, Uk, 18-19 December 1989 |journal=Aspects of Applied Biology |volume=23 |pages=269–276}}

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.{{cite journal |last1=Cedden |first1=Doga |last2=Güney |first2=Gözde |last3=Scholten |first3=Stefan |last4=Rostás |first4=Michael |title=Lethal and sublethal effects of orally delivered double-stranded RNA on the cabbage stem flea beetle, Psylliodes chrysocephala |journal=Pest Management Science |date=2024 |volume=80 |issue=5 |pages=2282–2293 |doi=10.1002/ps.7494|pmid=37020381 |url=https://publications.goettingen-research-online.de/bitstream/2/125521/1/10.1002ps.7494.pdf }} 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.{{cite journal |last1=Cedden |first1=Doga |last2=Güney |first2=Gözde |last3=Debaisieux |first3=Xavier |last4=Scholten |first4=Stefan |last5=Rostás |first5=Michael |last6=Bucher |first6=Gregor |title=Effective target genes for RNA interference-based management of the cabbage stem flea beetle |journal=Insect Molecular Biology |date=2024 |doi=10.1111/imb.12942|doi-access=free |pmid=38970375 }} 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.

{{Reflist}}

• [http://www.thewcg.org.uk/chrysomelidae/0195G.htm High reoslution images of Psylliodes crysocephala]

{{Taxonbar|from=Q586373}}

Category:Agricultural pest insects

Category:Beetles of Europe

Category:Taxa named by Carl Linnaeus

Category:Alticini

Category:Beetles of North America

Category:Beetles described in 1758