Small white cabbage butterfly

Pieris rapae

1. Identification

• Common name: Small white cabbage butterfly
• Scientific name: Pieris rapae L.
• Order: Lepidoptera
• Family: Pieridae

2. Pest description

• Adults: Small butterflies (≈ 40–50 mm wingspan); white wings with darkened tips on the forewings; females with two circular black spots.
• Larvae: Yellowish-green caterpillars, with a light dorsal line and very fine hairs; up to 25–30 mm long; solitary behaviour.
• Eggs: Yellow, elongated, laid singly on the underside of the leaves.

3. Main hosts

• Cultivated Brassicaceae: white cabbage, cauliflower, broccoli, kale, turnip, radish.
• Wild Brassicaceae (Sinapis spp., Raphanus spp., Brassica spp.).

4. Symptoms and damage

• Irregular perforations in the leaf blade.
• Moderate to severe defoliation, especially in young plants.
• Less extensive damage than Pieris brassicae, due to the solitary behaviour of the caterpillars.
• Contamination of the leaves with excrement, reducing the commercial value.

5. Biological cycle

• Winter spent as a chrysalis in shelters in the vegetation or structures.
• Adults emerge in early spring, with several generations per year.
• Females lay eggs singly on the underside of the leaves.
• Caterpillars develop for 2–3 weeks before pupation.
• 3 to 5 generations per year, depending on weather conditions.

6. Monitoring

• Observation of the underside of the leaves to detect isolated eggs.
• Counting of young caterpillars.
• Visual monitoring of adults in flight during spring and summer.
• Assessment of defoliation in sensitive crops.

7. Management measures

• Cultural: Manual removal of eggs and caterpillars; elimination of wild Brassicaceae; crop rotation.
• Biological: Conservation of natural parasitoids (e.g.: Cotesia rubecula); application of Bacillus thuringiensis directed at the control of caterpillars in early stages.
• Integrated protection: Intervention based on monitoring; preference for selective products compatible with natural enemies; avoid late treatments due to lower efficacy on developed caterpillars.

Bibliographic references

• EPPO Global Database – Pieris rapae.
• CABI Invasive Species Compendium – Pieris rapae.
• Alford, D. V. (2007). Pest and Disease Management Handbook.
• Salisbury, A. et al. (2015). Ecology and management of Pieris species.