Defra

Adult butterfly (wingspan 1.5-2.7cm)

The Geranium Bronze butterfly is a native of southern Africa, where it feeds on wild Geranium spp.. It was accidentally introduced into the Balearic Island of Mallorca, Spain, probably in 1987, and since then it has spread to the other Balearic Islands (Menorca and Ibiza) and other countries in southern Europe. The Geranium Bronze occurs on cultivated geranium (Geranium and Pelargonium) species in Europe and can pass through five to six generations per year in Mediterranean locations. All cultivated geranium varieties are at risk, although studies in Mallorca suggested that preferred cultivars include zonale and peltatum.

The adult is small and bronze-coloured with a wingspan of about 1.5 to 2.7 cm. The outer margin of the forewings is decorated with white dashes, and there is a white band around the edge of the hindwing. Each hindwing also has a black eyespot and a small 'tail'.

The small (0.5 mm), yellow-white eggs of the butterfly are laid on buds or on the underside of leaves. After emerging from the egg, the tiny (1 mm) larvae bore into the plant, where they feed and develop. They eventually grow up to 1.3 cm in length, and mine the plant, including the stems. The larvae vary in colour between yellow and green, with stiff white hairs, and sometimes have pink markings along their body. The pupae gradually develop a brown mottling and are often found within plant stems, although they also occur on the ground in leaf litter.

The Geranium Bronze butterfly spread to mainland Spain in 1993, and to the south of France in 1997. By December 2000, it had spread widely within the south of France, and has also been recorded in Italy, Belgium and Morocco. Although the butterfly is not established in the UK, the discovery of a breeding population in two private gardens in East Sussex in 1997 indicated that the UK's summer climate is suitable for the development and reproduction of this species. This colony died out, and the Geranium Bronze butterfly is not considered to be able to survive outdoors over winter in the UK. However, the movement of geranium cuttings, or plants, indoors in the autumn could provide it with an opportunity to survive the winter, until plants are returned to their summer sites.

Defra's Plant Health and Seeds Inspectorate (PHSI) have surveyed around the site of the 1997 outbreak, near Lewes, East Sussex, and apart from a couple of sightings in 1998, no other Geranium Bronze butterflies have been observed in this area. However, a third sighting of the butterfly occurred in Dorset in August 2001. The PHSI are continuing to monitor geranium imports, but because of the cryptic habits of the larvae, they also rely on reported sightings of the pest.

Cacyreus marshalli is listed as an A2 quarantine pest by the European and Mediterranean Plant Protection Organisation (EPPO).

Examine rooted geranium cuttings when they are brought in during the winter. Husbandry techniques - such as propagation via stem cuttings, removal of damaged tissue, deadheading, pinching out of growing-tips and pruning - present opportunities to examine plants for signs of infestation. Also examine geraniums in pots, tubs and hanging baskets for signs of infestation.