Cabbage worm : which symptom ? How to eliminate it ?

As its name suggests, the cabbage butterfly is a parasite which attacks different species of cabbage and many other plants of the family of Brassicaceae (formerly Cruciferaceae). Let’s find out what pest which it is strongly recommended to eliminate without delay. Let’s take this opportunity to take stock of the symptoms caused by the cabbage butterfly, and see one by one the possible treatments and the best means of prevention.

What is cabbage butterfly?

It is between the month of April and the end of October that this papillon flies over the gardens. In the space of 6 months, it can cause enormous damage to crops. The female lays dozens of eggs under cabbage leaves during the spring.

The gardener has every interest between May and June to watch the underside of the leaves of his cabbages of all kinds in order to look for the white butterfly eggs. They do not measure more than a millimeter in length. They are grouped together, have vertical streaks and look like small shells. Regarding their color, it changes over time: from creamy-white when they have just been laid, the eggs of the cabbage butterfly turn yellow and then orange when they are about to be laid. to hatch.

In barely a week to 10 days, the green caterpillars hatch eggs and feed on cabbage leaves. They may be small, but they show a great voracity. After some time, they become yellowish-green with black spots and hairs can be seen on their bodies.

When they reach the size of 4 cm, they leave the host plants and it only takes them a fortnight to turn into a butterfly whose lifespan is limited to about 21 days. But that is more than enough for the cycle to repeat itself: the females come to lay eggs in the cabbage and so on, the flight and egg-laying episodes succeeding one another, so that in the space of 6 to 7 months, the gardener can undergo three generations of cabbageworms.

Note that when the last caterpillars of the season are transformed into chrysalises, they remain in this state all winter. So they hibernate until spring.

What are the symptoms caused by cabbageworm?

Almost all cabbages are exposed to a cabbage butterfly attack as well as other cultivated or wild plants of the same botanical family as cabbages. This pest can therefore infest, among other things:

  • kale,
  • Cauliflower,
  • broccoli cabbage,
  • headed cabbage,
  • Brussels sprouts,
  • kohlrabi,
  • The mustard,
  • The rapeseed,
  • Wild plants also belonging to the family of Brassicaceae such as sea kale or Cochlea officinalis.

The symptoms suggesting the presence of the cabbage butterfly are the following:

  • Of the holes more or less numerous at the level of cabbage leaves located outside,
  • An accumulation ofexcrement between the leaves,
  • Of the shredded leaves of which only the thickest veins remain.

When the cabbage leaves are heavily soiled by the excrement of the white butterfly caterpillars, they can no longer be eaten. You really have to take the problem seriously because a major infestation of cabbageworms can destroy an entire culturecausing significant financial losses.

How to eliminate cabbageworm?

There is no other solution than process as soon as possible before it’s too late, that is, before the beautiful cabbages in the garden turn into emaciated carcasses.

The gardener can opt for sprays :

  • D’infused absinthean insect repellent (i.e. a product that repels insects) effective because of the strong odor given off by absinthe,
  • Of pyrethruma natural insecticide extracted from Tansy,
  • Of Bacillus thuringiensis (Bt), a species of Gram-positive bacteria used worldwide as a natural insecticide that is perfectly compatible with organic farming. Bt also helps eradicate processionary caterpillars…

It is also possible to use parasites to conduct a effective biological control against the cabbage butterfly. For example, thehymenoptera Apanteles glomeratus lays its eggs in the body of the Pieris caterpillars. These are parasitized and die. It may therefore be interesting to install nesting boxes near a cabbage bed in order to attract them to be quiet. But they are not the only allies in this area: wasps, syrrhesis et chrysopes love cabbageworm eggs and caterpillars. On good terms…

Means of preventive control against the cabbage butterfly

As it is better to prevent than to cure, the gardener has every interest in auscultating the underside of the leaves of his cabbages in order toremove manually Few white butterfly eggs that he could find there or even the caterpillars.

It can be cautious by installing near the cabbages of companion plants that scare away pest butterflies. In this category, we find for example thyme, mint, tomato, basil, sage, wormwood, rosemary, celery, verbena.

Be careful, however, not to make the mistake of planting plants there that attract the butterflies of the cabbage butterfly, which is the case of the nasturtium. Before making associations with the vegetable garden, you should always find out about the benefits that can be drawn from them.

Photo credit: Schnobby

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