Draft data sheet for Cacyreus marshalli
The French Plant Protection Service, in cooperation with INRA and the Horticultural College in Angers, have produced (in French) a "Guide to the field recognition of the main host species of fireblight". Enforcement of regulations to limit the spread of Erwinia amylovora (EPPO A2 quarantine organism) depends on being able to distinguish host plants, and this publication would be extremely useful in all EPPO countries, whether they are seeking to prevent the spread of fireblight on their territories, or needing to certify material for export.
French Plant Protection Service (1992-06)
CACYMA....Draft data sheet for Cacyreus marshalli
At the 30th Meeting of the EPPO Working Party on Phytosanitary Regulations the participants decided to consider Cacyreus marshalli, a pest of Geranium and Pelargonium spp., as a pest of potential quarantine significance. The Working Party recommended that countries which import Geranium and Pelargonium spp. should thoroughly examine the material for eggs and larvae of the butterfly. They stressed the danger that the pest might spread from Mallorca to the continent by individual tourists carrying infected plant material.
A description of the pest is given in the attached draft data sheet provided for the Working Party
Name: Cacyreus marshalli Butler
Taxonomic position: Insecta: Lepidoptera: Lycaenidae
Synonyms: none known
Common Names: none known
EPPO Code: CACYMA
EPPO A2 list: candidate
Geranium and Pelargonium spp. are the host plants of this butterfly.
The species is indigenous to southern Africa (Clark & Dickson, 1971). It was found in Spain (Mallorca, Balearic Islands) in 1988 and was first misidentified as Lycaena boeticus (Sarto i Monteys & Maso, 1991). It is now widespread on Mallorca. In 1991, one adult specimen of C. marshalli was found in Belgium (Troukens, 1991).
EPPO region: Spain (Mallorca only)
Africa: Mozambique, South Africa, Zimbabwe.
Little is known about the biology of C. marshalli since the butterfly was first found in Europe in 1988 and only correctly identified in 1990 (Eitschberger & Stamer, 1990). It obviously did not cause significant enough losses in its indigenous area, southern Africa, to justify specific research.
After its discovery in Mallorca, the Plant Protection Service of the province of Catalu¤a started a research project on the biology of the pest (Sarto i Monteys & Maso, 1992). The newly hatched larvae move into a flower bud by piercing a hole through the sepals. They remain concealed in the flower buds and feed on the flower tissue, where they produce a cavity as a result of their feeding. On reaching the third instar, the larvae leave the flower bud by initiating a gallery into the stem. At 20ø C, the larvae complete their development to pupae in about 30 days and the pupal stage lasts about 17 days (Sarto i Monteys & Maso, 1992). At lower temperatures, development is slower and it is assumed that the pest cannot overwinter in colder regions. At laboratory conditions of 20ø C, no diapause has been observed and the generations follow each other continuously (Maso & Sarto i Monteys, 1991).
Detection and identification
The damage becomes most visible during the hot season when the larvae are most active. Flower damage is the most visible symptom. Flowers can be totally eaten by the larvae. Damage can be seen on flower peduncles and is often associated with secondary damage by microorganisms which can also colonize the tissue around the entry hole of the larvae into the peduncles (Sarto i Monteys & Maso, 1991).
Leaves may be partially eaten by the larvae but this symptom is less frequent and can be confused with feeding by snails (Sarto i Monteys & Maso, 1991). Eggs can be found on leaves and flowers. Seriously affected plants may die as a result of the infestation.
Eggs: whitish to light yellow or brown in colour; 0.5 mm in diameter x 0.3 mm in height.
Larvae: First instar larvae have an average size of 1 mm which increases to 2 mm within 8 days. Second, 3rd and 4th instars grow to 3, 6 and 13 mm, typically in 8, 8 and 9 days respectively. The colour varies, with extremes of yellow and/or greenish shades with or without pink markings (Clark & Dickson, 1971).
Pupae: Very hairy in shades of green, pale yellow or brown, with brown mottling and an average size of 9 mm (Clark & Dickson, 1971).
Adults: Female adults have a wingspan of 18-27 mm while male adults have 15-23 mm. C. marshalli has a bronze-brown colouring of the upper surface with white spots on the fringe.
Means of movement/dispersal
The potential for natural spread is obviously very low. The flight is short in duration, leisurely and interspersed with frequent rests. Eitschberger & Stamer (1990) therefore excluded the possibility that the introduction into Mallorca was due to natural dispersal. The most possible means of international dispersal is the movement of infested plant material, since larvae cannot easily be detected because of their habitat within the stem.
Little is known on the economic importance of this pest in its indigenous area. In Mallorca, 99% of pelargoniums are reported to be affected by C. marshalli (Sarto i Monteys & Maso, 1991).
The Spanish authorities have regarded the eradication of this pest as impossible since chemical treatments seem to have very little effect on the stem-living larvae (Sarto i Monteys & Maso, 1992). The only stage in the life cycle of C. marshalli when insecticides are likely to show results is during the egg stage.
In Mallorca, no parasites have been found (Sarto i Monteys, pers. comm.). In South Africa, Apanteles spp. have been reported to kill third-instar larvae of the pest (Clark & Dickson, 1971).
C. marshalli has not yet been listed as a quarantine pest by any RPPO. The example of the rapid establishment of C. marshalli on Mallorca shows that the pest has potential to establish in the Mediterranean basin and can be considered as a real danger for the European mainland. Pelargoniums are extensively grown as ornamental plants almost throughout Europe, but Spain, France and Italy, as well as North Africa, are at highest risk since their climatic conditions would allow the pest to overwinter outdoors. Furthermore, breeding and propagation of pelargoniums plays an important economic role in this region. Elsewhere in Europe, the pest could establish in glasshouses.
The danger that the pest "jumps" from Mallorca to the mainland is rather high since Mallorca is one of the major tourist areas of Spain.
While the pest has a very restricted distribution in Europe, great vigilance is needed to prevent its establishment in new areas. Area freedom for planting material is the most obvious immediate measure. If the pest readily establishes and persists throughout the season in an area, it may be very difficult to ensure that nurseries producing pelargonium planting material can be certified free from the pest.
Clark, G.C.; Dickson, C.G.C. (1971) Life histories of the South African Lycaenid butterflies. pp. 270, Purnell Cape Town, 60-61.
Eitschberger, U.; Stamer, P. (1990) Cacyreus marshalli Butler, 1898, eine neue Tagfalterart für die europäische Fauna ? Atalanta 21 (1/2), 101-108.
Maso, A.; Sarto i Monteys, V. (1991) Una mariposa amenaza al geranio europeo. Cienca y Tecnologia 23 Noviembre 1991, p 9
Sarto i Monteys, V.; Maso, A. (1991) Confirmacion de Cacyreus marshalli Butler, 1898 (Lycaenidae: Polyommatinae) como nueva especie para la fauna europea. Boletin de Sanidad Vegetal Plagas 17, 173-183.
Sarto i Monteys, V.; Maso, A. (1992) Remarks on the biology of a lycaenid butterfly, pest of geraniums, new to Europe (Lycaenidae). Speech at the VIII European Congress of Lepidopterology, Helsinki, 19-23 April 1992.
Troukens, W. (1991) Cacyreus marshalli Butler, 1898 aangetroffen in België (Lepidoptera: Lycaenidae). Phega 19 (4), 129-131.
EPPO Secretariat, Paris (1992-06)