|At the beginning of summer 2001, INRA (Institut National de
la Recherche Agronomique) in Antibes (France) was alerted by people from the
Department of Var that they had a lot of palm trees severely damaged by a
“white grub,” and some palms had even died. It was the starting point for an
official report of a new exotic moth introduced accidentally into France.
This beautiful insect – the largest introduced accidentally into Europe – is
indeed a serious pest for a great number of palm species.
The scientific name for this moth is Paysandisia archon
Burmeister; it belongs to the family Castniidae (Lepidoptera), most members
of which live in South America.
The adult is a beautiful moth, with a large wingspan of 9–11 cm. The
fore-wings are olive brown-coloured and the hind-wings are brightly coloured
with red, black and white (Fig. 1). The
antennae are clubbed. Females are a little larger and are easily
recognizable by their chitinous ovipositor at the end of the abdomen. The
eggs are laid separately; they are oblong (5 mm long), cream-coloured and
with longitudinal ribs (Fig. 2). Just after
hatching, the larva is pink-coloured and less than 1 cm long, but turns
white as it grows. It reaches 6–7 cm at the end of its development, looking
a bit like a grub, and with four pairs of pseudopods (Fig. 3).
The moth is native to the central region of Argentina and neighboring
Uruguay where it lives on palms, Trithrinax campestris among other
species. Trithrinax campestris grows in the wild on the plateau of
the central northern part of Argentina (east of Cordoba) where up until the
present is very common. However, as shown in Gibbons’ paper (2001), this
palm (el Caranday) seems now to be threatened in its native country. There
is a huge need for agricultural land in Argentina, and so T. campestris
has to be eliminated as land is cleared for fields. For this reason, a
great number of them are burned or at best uprooted for commercial purposes.
They are exported to other countries, such as in Europe, where they are
first put together in the same site before they are sold and spread to other
north Mediterranean places.
In France, Paysandisia archon is presently localized in the
Department of Var, between Toulon and Hyères (Fig. 4) where
it has been introduced most probably with imported Trithrinax from
Argentina. It is also recorded in Spain, in the area of Girona (Catalonia)
with the same probable origin (Aguilar 2001). Until now, no record has been
officially reported in other Mediterranean countries, although it is likely
to be present in Italy as well. It arrived in France a few years ago
(probably about 1995) but its presence was not notified at that time and the
official record with accurate scientific identification was only made in
July 2001 (Drescher & Dufay 2001). With the increasing interest in palms in
all the towns of the south of France, it is likely that the dispersal range
of this pest will enlarge to other areas of the region in the near future.
Very few data are available on P. archon in the literature. The
main reason is that it is not considered as a pest in its native country,
probably due to the presence of natural enemies (parasites and predators),
which limit its populations, but also to the fact that it lives originally
on palm trees growing naturally and not on crops. Its life cycle has not
been studied in Argentina. Only one author, F. Bourquin, has written a small
paper with some biological information on this moth, in an Argentinian
journal (Bourquin 1933).
The few observations made in France suggest that the moth has a long
cycle of development. The adults are observed from June to September. They
are active during the day. All stages of development, from egg to chrysalis
have been recorded at the same time, in July. The egg is laid at the basis
of the leaf on the stem or in the terminal bud. The larva bores a gallery (Fig.
3) through the stem or through the young leaves, not yet expanded at the
stem apex (in the terminal bud), causing characteristic damage (Fig.
5). When several larvae bore simultaneously in the stem, the palm
becomes weak (Fig. 6) and can even die. Except
for the period when the adults are flying, it is difficult to detect the
presence of the pest; at the larval stage the only sign may be the presence
of plugs of debris, like sawdust, visible at the outermost extremity of the
gallery (Fig. 7). The larva turns into a
chrysalis, protected by a cocoon made with palm fibres (Fig.
8), inside the gallery. At the very end of its development, the
chrysalis frees itself from the cocoon at the outermost extremity of the
gallery, and a new adult moth is born after tearing this envelope. The
remains of the chrysalis are often attached to the exit hole of the gallery
for a while.
In Argentina, P. archon was reported to attack native palms such
as Trithrinax campestris and Butia yatay, as well as
occasional exotic species such as Latania, Chamaerops or
Phoenix canariensis (Bourquin 1993). In France, the moth appears to have
a large range of hosts and can damage many different palms besides T.
campestris, for example Chamaerops humilis, Livistona chinensis, L.
decipiens, L. saribus, Sabal spp., Phoenix canariensis, P.
dactylifera, P. reclinata, Trachycarpus fortunei and Washingtonia
filifera. This list is probably not exhaustive and will have to be added
to following other future observations. In Spain, it has been observed on
Trachycarpus fortunei, Phoenix canariensis, Washingtonia spp. and
Chamaerops humilis (Aguilar 2001).
The damage is observed at different levels of the tree: leaves, rachis
and top of the stem. Once hatched, the larva bores towards the heart of the
palm and if several larvae are present on the same tree, this can lead to
the death of the palm. Big palms can survive if they are not too severely
attacked, but small ones or plants in the nursery or in containers are very
exposed to attack. It is this ability to feed on a large variety of palm
species that makes this pest a real threat to the future of palms in regions
of Europe where it has been accidentally introduced.
Unfortunately since this moth is not a pest in its native country, no
control method has been developed. Some chemicals must be tested before
being allowed to be uses in parks and gardens, but it is not certain how
effective they can be in reaching the larva hidden inside the trunk.
Biological control (i.e. the use of natural enemies) could be another
possibility, safer for the environment, but it needs several years for
As far as we know to date, this pest has been observed in only two
limited areas (in France and in Spain), but Paysandisia could spread
to a much larger region if no severe measures are taken. In France, this
pest has been recently included in the list of noxious organisms submitted
for compulsory control measures (Official Journal, February 2002). With the
large number of palm species susceptible to its attacks, the moth could
seriously threaten the palms that represent a large part of the tourist
image of the south of France. The international trade in mature palm trees
must be severely limited and controlled to prevent pests from being
introduced (other exotic pests have been recently discovered on imported
palms in France and in the soil around their roots), because this practice
can lead to severe damage to already established palms. It is the role of
palm lovers to be aware of this serious problem and to act in order that the
object of their passion can live safely for many years; any observation of
new or suspected damage on trees must be notified to experts.
AGUILAR, L.L. 2001. A new lepidopteran family for the European fauna.
SHILAP Rev. Lepid. 29: 86–88.
BOURQUIN, F. 1933. Notas biologicas de la Castnia archon Burm. Rev. Soc.
Ent. Argentina 24: 295.
DRESCHER, J. AND A. DUFAY. 2001. Un nouveau ravageur des palmiers dans le
sud de la France. PHM-Revue horticole 429: 48–50.
GIBBONS, M. 2001. Trithrinax, trials and tribulations. Palms 45:
JOURNAL OFFICIAL. 21 fév 2002, p. 3371.
LEPESME, P. 1947. Les insectes des palmiers. P. Lechevalier, 903 p.