Pieris rapae (small cabbage white)

Pieris rapae (small cabbage white)

© Christian Bauer

Type: Pests


Caterpillars

Caterpillars can very quickly cause considerable damage to crops, particularly brassicas. They are the larval stage of butterflies and moths - on brassicas, normally the large white (Pieris brassicae) , the the small white (Pieris rapae) or the cabbage moth (Mamestra brassicae).


Symptoms

Aside from the caterpillars themselves which reach 3-4cm in length and can be very numerous:
  • Yellow eggs on the undersides of leaves
  • Holes in leaves
  • Dark droppings at the base of leaves where they collect

Prevention & control

  • Netting will physically prevent attacks but make sure it's held well away from leaves to prevent laying eggs through the netting
  • Encourage natural predators such as wasps
  • Look for and crush any eggs on the underside of leaves
  • Once holes appear, pick off the caterpillars - those of the small white butterfly are green and can be difficult to spot as they lie along the leaf veins.
  • In serious cases:
    • Spray with Bacillus thuringiensis
    • Spray with pyrethrum
    • Apply a nematode treatment
    But be aware that these will affect all caterpillars.
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