Geranium bronze moth

Cacyreus marshalli

1. Identification

• Common name: Geranium bronze
• Scientific name: Cacyreus marshalli Butler
• Order: Lepidoptera
• Family: Lycaenidae

2. Pest description

• Greenish‑brown caterpillars, about 10–12 mm, developing inside the plant tissues.
• Small adults, with brown wings on the upper face and a pale pattern on the lower face; wingspan of 15–23 mm.
• Leafmining and boring species, feeding on stems, flower buds and flowers.
• Invasive pest, widely spread in urban and ornamental environments.

3. Main hosts

• Geranium.
• Ivy geranium.
• Other ornamental species of the genus Pelargonium spp..

4. Symptoms and damage

• Perforations and galleries in stems, causing wilting and breakage of branches.
• Perforated flower buds, which dry out before opening.
• Damaged flowers, with petals partially eaten.
• Progressive decline of the plants, which may lead to death in severe attacks.

5. Biological cycle

• Eggs laid singly on the leaves, buds or young stems.
• Caterpillars quickly penetrate the tissues, where they complete their development.
• Pupation inside the stems or in protected structures of the plant.
• Adults emerge from spring to autumn; several generations per year, accelerated by high temperatures.

6. Monitoring

• Observation of perforations in flower buds and stems.
• Search for internal galleries and necrotic tissues.
• Regular assessment of ornamental plants, especially during warm periods.
• Reinforced monitoring in nurseries and urban green spaces.

7. Management measures

• Cultural: removal and destruction of attacked parts; elimination of heavily infested plants.
• Preventive: inspection of acquired plants; avoid introducing infested plant material.
• Biological: promotion of natural enemies when present; use of Bacillus thuringiensis at young stages (variable efficacy due to the leafmining behaviour).
• Integrated protection: judicious use of authorised insecticides, targeted at the moments of greatest exposure of the caterpillars; integration with continuous monitoring.

Bibliographic references

• CABI – Invasive Species Compendium – Cacyreus marshalli.
• EPPO Global Database – Cacyreus marshalli.
• Alford, D. V. (2007). Pest and Disease Management Handbook. Blackwell Publishing.
• Sarto i Monteys, V. et al. (2005). Biology and spread of the geranium bronze. Journal of Applied Entomology, 129, 1–7.
• Gabarra, R. et al. (2008). Monitoring and management of Cacyreus marshalli in ornamental plants. IOBC/WPRS Bulletin, 38, 123–130.