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Biological control of the cabbage white butterfly, Pieris rapae

Updated on May 13, 2016
A caterpillar of Pieris rapae
A caterpillar of Pieris rapae | Source

How to control the Cabbage White Butterfly in an environmentally friendly way

The cabbage white butterfly, Pieris rapae is called the "Small Cabbage White Butterfly" in English speaking Europe, but the "European Cabbage Butterfly" or "Imported Cabbageworm" in America and Canada. It was introduced in North America from Europe at around 1860.

Caterpillars of the cabbage white live on a variety of crucifers and can be damaging on cabbages.

Caterpillars can be up to 2.5 cm long. They are green with a thin yellow line along the body, and their green head is speckled with tiny black dots.

male small cabbage white
male small cabbage white | Source

Appearance of Pieris rapae males

Males of the small cabbage white butterfly, Pieris rapae, (Order: Lepidoptera; Family: Pieridae) have white wings with a small, dark spot at the corner of the fore wings and one round, black spot closer to the centre of each fore wing.

The wing span is about 4 cm.

Female small cabbage white
Female small cabbage white | Source

Appearence of Pieris rapae females

Females of the small cabbage white butterfly have, similar to the males, white wings with a small, dark spot at the corner of the fore wings, but they have two round, black spots closer to the centre of each fore wing, instead of one.

The wing span is about 4.5 cm.

Biology of the small cabbage white

Pupa of the small cabbage white
Pupa of the small cabbage white | Source

The butterflies that have overwintered as pupae appear in spring. They are active during day time and mate towards mid-day, after which the couple flutters around for up to two hours. Eggs are laid singly on the underside of leaves of mainly wild crucifers. The caterpillars pupate on the host plant, and the next generation butterflies lay eggs on cabbages in June. These caterpillars pupate in sheltered places in August-September and overwinter.

Damage of the small cabbage white butterfly

Damage on curley cale
Damage on curley cale | Source

It is especially the second generation caterpillars that is damaging to cabbages. With heavy infestations they leave sometimes only the main veins of the leaves. Moreover, they bore into hearts of cabbages and deep into curds of cauliflower, unlike the caterpillars of the large cabbage white butterfly (P. Brassicae), which only attacks the open leaves. The plants can therefore be fouled by the accumulation of droppings, which causes decomposition resulting in an unpleasant smell.

Larvae of Cotesia (Apanteles) glomeratus emerge from a parasitized caterpillar
Larvae of Cotesia (Apanteles) glomeratus emerge from a parasitized caterpillar | Source

Natural enemies of the small cabbage white

Many caterpillars will be eaten by birds, especially tits, and wasps (Order: Hymenoptera; Family: Vespidae). Caterpillars are also attacked by small, parasitic wasps, such as Cotesia (Apanteles) glomeratus (Order: Hymenoptera; Family: Braconidae).

This species deposits eggs in young caterpillars, which grows to maturity with the developing larvae inside. Just before it is ready to pupate, the wasp larvae eat its vital parts and eventually crawl out of the dead caterpillar, and pupate on its skin.

Another parasitic wasp, Pteromalus puparum (Order: Hymenoptera; Family: Pteromalidae) attacks the pupae of the small (and also the large) cabbage white butterfly.

Treatment

  • Fine-mesh netting or horticultural fleece will stop butterflies from reaching the crop and lay eggs. The barrier must be complete and without any holes, however, as the butterfly is capable of finding the tiniest holes! When you do find eggs or caterpillars - usually on the underside of the leaves - pick them off by hand.
  • Consider placing nest boxes for tits, as their young need large quantities of caterpillars for their development.
  • For biological control one could apply Trichogramma, which are tiny wasps that parasitize eggs. Trichogramma can be purchased from biological control companies.
  • Do not destroy any wasp nests: the wasps will capture many of the caterpillars to feed their young with.
  • Intercropping cabbages with Nastatium, Tropaeolum majus or Chamomile, Matricaria recutita results in fewer eggs laid on cabbage by the butterflies, according to this article.

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    • mechanicaleye profile image

      Eda Ċ kulj 4 years ago from Bosnia and Herzegvina

      I also knew that planting chamomile is effective, but I was not aware that wasps also help. Thanks for the tips, I'll make sure the wasp nests I find in the future stay intact.

    • caffimages profile image

      caffimages 5 years ago

      Thanks for the tips. The birds do help! I'll look after any wasps I find from now on.

    • marlies vaz nunes profile image
      Author

      Marlies Vaz Nunes 5 years ago from Amsterdam, the Netherlands

      @marlies vaz nunes: I found that planting chamomile and also nastatium between cabbages results in fewer eggs and caterpillars. I added it to the treatment list. Thanks for mentioning it!

    • marlies vaz nunes profile image
      Author

      Marlies Vaz Nunes 5 years ago from Amsterdam, the Netherlands

      @anonymous: I haven't heard of this. I'll find out and let you know. (BTW it is "true" ;-) )

    • profile image

      anonymous 5 years ago

      I was told you have to plant Chamomile next to you cabbage, do you know it that is trough?

    • marlies vaz nunes profile image
      Author

      Marlies Vaz Nunes 5 years ago from Amsterdam, the Netherlands

      @aesta1: Thank you. There will be many more coming.

    • aesta1 profile image

      Mary Norton 5 years ago from Ontario, Canada

      You have interesting lenses. I don't know much about these so I appreciate your putting them up here.