Cabbage-stem flea beetle (Psylliodes chrysocephala): how to control it biologically?

The cabbage-stem flea beetle is one of the most serious threats to rapeseed cultivation. This formidable beetle is particularly active during critical periods for your rapeseed sowing. Find out everything you need to know about this pest, and above all, what biological measures to apply to protect your crops.

Description of the cabbage-stem flea beetle (Psylliodes chrysocephala)

The cabbage-stem flea beetle, Psylliodes chrysocephala , is a beetle that belongs to the Chrysomelidae family. It is also called the winter flea beetle.

• The adult : it is blue-green in color with metallic reflections. It can measure up to 4.5 mm long.
• The larva : it reaches 8 mm until its last larval stage, is yellowish or creamy-white in color, with a brown-brown head and thorax.

Development cycle of the cabbage-stem flea beetle

After overwintering in the soil, adults become active as early as May, but it is in late summer, when rapeseed is sown, that their activity becomes particularly problematic.

Females lay their eggs in autumn and late winter, and the resulting larvae enter the plant by tunnelling through the petiole of older leaves.

During the summer, these flea beetles go into diapause, seeking refuge under the dense foliage of hedges, bushes, and other field edges. This summer break allows them to protect themselves from unfavorable climatic conditions while waiting for the rapeseed sowing period, when they become particularly active.

Females lay their eggs in autumn and late winter, and the resulting larvae enter the plant by tunnelling through the petiole of older leaves.

What damage is caused by cabbage-stem flea beetles?

These insects, both in adult and larval stages, mainly attack young rapeseed plants.

Damage caused by adults

As soon as the rapeseed emerges, the adults of the large flea beetle begin to feed on the young leaves . They are mainly active at night, which often makes their early detection difficult. You will notice their presence by the circular holes or bites they leave on the leaves, stems, and sometimes even on the pods. These bites weaken the young seedlings, making the plant less vigorous and more susceptible to other stresses.

In case of heavy infestation, adults can completely destroy young plants before they can even develop properly. This represents a major risk for the success of your crop, especially if the damage occurs in September, when the seedlings are still young and vulnerable .

Damage caused by larvae

Cabbage-stem flea beetle larvae, after hatching, enter the plant through the leaf petiole. From there, they tunnel inside the stems , eating away at the pith of the leaves. This process not only weakens the internal structure of the plant, but can also cause the larvae to migrate to the collar and then the stem, seriously compromising the plant’s ability to grow and produce.

This results in a decrease in your crop yield, which significantly affects the profitability of your operation if these attacks are not managed effectively.

Critical periods of observation

Attacks by cabbage-stem flea beetles are particularly visible in two periods: September and spring . It is during these times that your rapeseed crops are most vulnerable, due to the increased activity of adults and larvae. By being vigilant during these periods and observing the first signs of damage, you can intervene quickly to limit the impact of these pests.

How to fight against the cabbage-stem flea beetle?

Biological control of these pests therefore relies on increased vigilance from the first appearance of flea beetles, combined with the use, from planting, of biostimulants and natural preparations to strengthen the resistance of the plants .

The use of biostimulants is the first line of defense against diseases and pests. Some biostimulants and basic substances have insecticidal and repellent effects against flea beetles (nettle manure). Application from sowing at the 1 to 2 leaf stage is recommended.

Agrobiotop solutions against the large flea beetle:

If you would like advice on the application of these biostimulants, please contact us .