AFPP – PALM PEST MEDITERRANEAN CONFERENCE NICE – 16, 17 AND 18 JANUARY 2013

PAYSANDISIA ARCHON (CASTNIIDAE): DESCRIPTION, BIOLOGICAL CYCLE,

BEHAVIOUR, HOST PLANTS, SYMPTOMS AND DAMAGES

V. SARTO I MONTEYS Departament d'Agricultura, Ramaderia, Pesca, Alimentació i Medi Natural de la Generalitat de Catalunya, Servei de Sanitat Vegetal, Avinguda Meridiana, 38, 08018 Barcelona, Spain, vsarto@gencat.cat SUMMARY Paysandisia archon is a Neotropical moth belonging to the family Castniidae (Lepidoptera), introduced into Europe with imported palms from Argentina, first reported in 2001 from Catalonia (Spain), which has spread to most European countries in the Mediterranean basin. This paper summarizes the accumulated knowledge on this moth, describing its different life stages, its life cycle, the behaviour of its larvae and adults; it also mentions the host plants the moth uses (all palm trees) and the symptoms of infestation on such plants as well as the damages produced on them. Key-words: Paysandisia archon, Castniidae, palm pest, life cycle, hostplants. RÉSUMÉ PAYSANDISIA ARCHON (CASTNIIDAE): DESCRIPTION, CYCLE BIOLOGIQUE, COMPORTEMENT, PLANTES HÔTES, SYMPTÔMES ET DOMMAGES Paysandisia archon est un papillon néotropical appartenant à la famille des Castniidae (Lepidoptera), introduit en Europe avec des palmiers importés d'Argentine, signalé pour la première fois en 2001 de Catalogne (Espagne), qui s'est étendu à la plupart des pays européens du bassin méditerranéen. Cet article résume les connaissances accumulées sur ce papillon, décrit ses différents stades, son cycle de vie, le comportement de ses larves et adultes; il mentionne aussi les plantes hôtes utilisées par le papillon (toutes sont des palmiers) et les symptômes d'infestation sur ces plantes ainsi que les dommages occasionés. Mots-clés : Paysandisia archon, Castniidae, ravageur de palme, cycle de vie, plantes hôtes.

INTRODUCTION

Paysandisia archon (Burmeister, 1880) is a Neotropical species of Castniidae (Lepidoptera) which was introduced into Europe with imported palms from Argentina, first reported in March 2001 from Catalonia (Spain) (Aguilar et al. 2001). Since then it became a serious pest of palm trees and spread to several European countries, mostly around the Mediterranean basin. It occurs permanently in Portugal, Spain, France, Italy, Switzerland, Slovenia, Greece, Cyprus and Bulgaria. It has also been found occasionally in northern countries like the United Kingdom and Denmark.

DESCRIPTION

The adults are big and beautiful moths (Fig. 1), they have greenish brown forewings, whereas the hindwings are orange, with a wide transverse black band containing five or six white cells. Their antennae are clubbed. Specimens reared from larvae in Catalonia showed the following wingspan: males, mean 7.48 cm (n=18; range: 8.6–6.2); females, mean 8.62 cm (n=22; range: 9.8–6.8). There is a subtle sexual dimorphism.

Figure 1: Adults of P. archon. Top: Female showing ovipositor partly extruded. Bottom: Male. Notice the butterfly-like antennae in both sexes.

(Adultes de P. archon. En haut : Femelle montrant l’ovipositeur partiellement extrudé. En bas : Mâle. NB : les antennes sont semblables à celles des papillons de jour chez les deux sexes).

Females bear a long telescopic ovipositor (1.5-2 cm when fully exerted), which is easily seen when gently pressing their abdomen, their wing-coupling is mediated through six to nine long and fine frenular bristles (males have only one long and stout frenular bristle), the dorsal part of their abdomen clearly shows six anatomical segments (as opposed to seven in males) and are generally bigger than males. Both sexes generally bear a light grey teardrop-shaped stigma on the forewings, which occurs somewhat more often in females; however, those last two characters (size and presence of stigma) cannot be used for sexing with certainty. Good colour illustrations of the adults can be found from many sources; the first ones were those of Oberthür (1914), Sarto I Monteys (2002) and Sarto I Monteys & Aguilar (2003). Houlbert (1918) and Miller (1986) contributed further morphological details, and the latter also figured and described for the first time the male and female genitalia as well as the labial palpus and the wing venation.

The egg (Fig. 2) is a typical castniid egg, fusiform, resembling a rice grain, bearing six to eight raised longitudinal ridges which have associated aeropyles along their length, with the micropyle at one end of the long axis.

Figure 2: Two hatched (2nd, 4th) and two freshly laid (1st, 3rd) eggs of P. archon. The micropylar region, quite small, is located at the very end of the long axis of the egg and cannot be seen in the photograph.

(Deux œufs éclos (2ème, 4ème) et deux œufs fraîchement pondus (1er, 3ème) de P. archon. La région micropylaire, assez petite, est située à l'extrémité de l'axe longitudinal de l'œuf et ne peut être vu dans la photographie.)

Their colour, when freshly laid, is creamy pink or light brown, becoming rosy brown as the days pass. The egg shell of hatched eggs appears dull white when seen on the fibre meshes of the palm; however, when illuminated under the stereomicroscope it shows a greenish tinge. Its length is 4.69 ± 0.37 mm (n=163), sample ranging from 5.45 to 3.67, the majority measuring between 4.4 and 5.2 mm. Its width, on the widest section, is 1.56 ± 0.11 mm, (n=118), sample ranging from 1.94 to 1.21, the

majority measuring between 1.50 and 1.60 mm. Full details on the morphology and biometry of the egg were provided by SARTO I MONTEYS et al. (2005).

The larvae (Fig. 3), endophagous, resemble those of big Cossidae (carpenter moths) and go generally through nine instars, increasing in size dramatically since hatching. After emergence, the body length is 0.73 ± 0.22 cm (n=5), the width of the head capsule at the widest part being 1.00 ± 0.10 mm (n=5). When full grown, but before entering the prepupal stage when some contraction takes place, the larva may reach a body length of 9 cm, width 1.5 cm at mid length, and the width of the head capsule at the widest part being 7.84 ± 0.34 mm (n=52).

Figure 3 : Larvae of P. archon. Left: First instar larva (just after hatching); Right: Late (7th or 8th) instar larva.

(Larves de P. archon. À gauche : Premier stade larvaire (juste après l'éclosion). À droite : Stade larvaire tardif (7ème ou 8ème).

After emergence the larvae are beautifully rosy (exceptionally only the dorsal vessel is rosy, being whitish the rest of the body), their chaetotaxy is different in the number and especially the length of the setae (much longer), and they do not present cuticular spinules. However, even through the first instar, the rosy colour fades towards whitish and the long straightlined setae become shorter because of multiple folding due to constant friction against the gallery walls where the larva lives. After the first moult, mobility diminishes notably, the colour of the larva becomes ivory white, chaetotaxy changes and the setae become much shorter, cuticular spinules appear; all these new traits are retained throughout the remaining larval stage, clearly indicating an endophagous condition. The pupae form inside a cocoon. The cocoons (Fig. 4) (average length 5.83 cm) are stout with inner walls smoothly coated by a layer of silk and mucus and outer walls loosely covered by fragments of palm fibres which makes them very cryptic. The pupae are pale yellowish at the beginning but later, darkening and hardening of the pupal cuticle occurs, until reaching, after about two days, a beautiful reddish brown colour (Fig. 4); this condition will remain unchanged until adult emergence.

Figure 4 : Left: P. archon cocoon, with pupal exuvia protruding and anchored on it. Right: Pupa in cut open cocoon.

(À gauche : cocon de P. archon, avec la chrysalide vide en saillie et ancrée sur le cocon. À droite : chrysalide dans un cocon ouvert)

A diagnostic protocol for P. archon as well as a set of colour photos depicting all life stages of this moth was provided by EPPO (2011).

BIOLOGICAL CYCLE

Egg hatching occurs after 12 to 21 days, according to temperature. The larval stage is the longest and most complex of all P. archon stages. It is the only one that overwinters; during winter time, nearly all instars can be found within the palms in the wild, including prepupal ninth instar larvae. Most larvae will undergo a one-year cycle, lasting ca. 10.5 months, although a second group will undergo an almost two-year one, lasting ca. 18.5 months. The prepupal larval stage is long and also complex, made up of two periods. The first occurs before making the cocoon and its length is very variable. The second occurs after the cocoon has been built and takes in the time spent by the larva inside the cocoon before converting into pupa; this time is around 17 days in early spring although it can be shortened to only 9 days in early summer. Pupae formed in the second half of March took an average of 66 days to complete their metamorphosis to adults; those formed in the first half of April took 52.33; those formed in the first half of July took 42.80. Live cocoons can be found from mid March to mid September. Adults appear in the wild in mid May and can be seen until late September, with a peak during June and July; sightings of adults in May, August and September are much rarer. Accordingly, live eggs are expected to be found from late May to mid October. In summary, the P. archon life cycle (in Catalonia, Spain) comprises, from egg to egg, an average of 389 days (i.e. 12.8 months) in specimens undergoing a one-year cycle and an average of 673 days (i.e. 22.1 months) in specimens undergoing a two-year cycle. Table I summarizes such a cycle (from Sarto I Monteys & Aguilar, 2005).

Table I : Life cycle of P. archon in Mediterranean climate. (Cycle de vie de P. archon en climat méditerranéen)

BEHAVIOUR

P. archon larvae emerge from the egg by gently splitting the chorion along the membrane contacting one of the longitudinal ridges, always on the half closer to the micropyle, one end of the split being just below the micropyle, the other end found about one-fourth to one-third the egg length (Fig.5). This operation, i.e. since the larval mandibles start splitting the chorion until the larva fully frees itself from the egg, may last for two to fifteen minutes, most larvae accomplishing it in about five minutes. Immediately after emergence the larvae start looking for food and shelter, both being obtained by boring into the hostplant; unlike other lepidopteran larvae, they do not eat the chorion.

Figure 5: Egg hatching in P. archon. Left: Larva cutting a window open through the chorion to get out from the egg. Right: SEM image showing the hatching split close to the mycropilar end.

(Éclosion des œufs de P. archon. À gauche : Larve coupant une fenêtre à travers le chorion pour quitter l'œuf. À droite : Image SEM montrant la déchirure d’éclosion proche de l'extrémité micropylaire)

Once into the hostplant the larvae will commence tunnelling and, normally, will not abandon it until the adult stage is reached. Thus, the larvae of P. archon are endophagous most of their lives, being exophagous only during the very short time needed from eclosion to entering the hostplant. Drescher & Jaubert (2003) reported that a set of newly emerged larvae took from 5 seconds to 3 minutes to enter the palm. P. archon larval feeding begins shortly after eclosion and continues until the larva reaches the prepupal stage (when feeding definitively stops), being interrupted by each and all moults. When the larvae enter a premoulting period they stop feeding and build a simple and loose chamber with chewed palm fragments and silk; sometimes this chamber is not very conspicuous. In there, the process of moulting will take place. We noticed that moulting pauses last for from about one to three days, the older the larva, the longer it takes. After the exuviae are shed a resting pause follows and the larva resumes feeding by normally (but not always) eating first the old skin. Some larvae may also try to eat their old head capsules, as we have sometimes recovered only fragments of them. It has also been observed that, sometimes, larvae taken from their galleries in the wild and placed in captivity in insectaries (thus undergoing stress), quickly enter a moulting period, which appears to be hasty or premature. These moults might well turn out to be supernumerary moults, as already known in other lepidopteran larvae. Indeed, under adverse conditions (nutritional or other), the number of larval instars in some Coleoptera and Lepidoptera can be increased (sometimes greatly), although there is little growth in size (Richards & Davies, 1977). P. archon larvae are cannibalistic in all their instars. Cannibalism does also affect prepupal larvae within their fully formed cocoons (in such a case, the cocoon will be perforated by another larva which will feed on the prepupal larva inside) (Fig. 6). Figure 6: Cannibalism in P. archon larvae. Left: Cannibalized cocoon. Right: Prepupal

larva cannibalized inside its cocoon; notice it misses half its body. (Cannibalisme chez les larves de P. archon. À gauche: cocon cannibalisé. À

droite : larve en prénymphose cannibalisée à l'intérieur de son cocon; NB : il manque la moitié de son corps).

The larvae are lucifugal and actively avoid being in direct light. When taken out of their galleries and placed temporarily in small plastic containers, with cellulose paper layers placed at the bottom, they quickly hide underneath those. When returned to fresh palm trunks, they immediately disappear under the layers of the fibre web that covers them, where will begin tunnelling again. Miller (1986) reported those traits too with other castniid species.

P. archon larvae move easily forwards and backwards within their galleries when disturbed, and can also turned around, helped with the short spinules mentioned above. Later instars are so stout that it is difficult, with only fingers, to extract them from their galleries when discovered, as they press their bodies onto the tunnel walls and use the numerous dorsal and ventral spinules as micro anchors. The larvae retain frass in portions of the excavated tunnel during development as well as expel it to the outside through the exit. Frass can also be found between layers of the fibre webs that wrap the trunk or blocking one end of the terminal gallery, i.e. that within which the larva will build the cocoon. Interestingly, sometimes, later instar larvae (not only the last instar), pack the frass in such a way that the resulting mass resembles very much (concerning its whole size, volume and shape) an actual cocoon. When those “false cocoons” appear between layers of the fibre webs that wrap the trunk, apparently with no connection to any gallery, this might represent, in its natural habitat in the Neotropics, a way of confusing likely predators or parasitoids. They can also be found blocking one end of the terminal gallery, providing some protection to the true cocoon. Indeed, those false cocoons confused us many times when looking for true cocoons in the trunks. P. archon larvae can be found tunnelling in different parts of the palms which largely depends on the larval size. Early instar larvae, because of their much smaller size, can be found, apart from in the trunks, within the fruits of Chamaerops humilis L. or within the leaf rachises (especially in Phoenix canariensis Hort ex. Chabaud and Washingtonia filifera (Linden ex André) H.Wendl.). In Trachycarpus fortunei (Hook.) H.Wendl., for instance, the first instar larvae can bore into the very young, packed and undeveloped palm leaves that spring from the palm crown; recall the eggs had been laid close to this location by the female; this piercing becomes later very obvious, as the leaf develops, opens and expands, showing a series of consecutive holes on a circular sector. The bigger the larvae the higher the probability to find them within the trunk. Large larvae will only be found within the trunk They tend to bore into and remain within the very core of those structures, where the humidity is higher and the temperature more stable. A cut piece of trunk (diameter 21 cm, length 35 cm) of T. fortunei palm kept in a rearing container in the lab can successfully host several larvae for two to three months with virtually no additional care. The multiple layers of fibre webs, tightly packed together around the trunk, keep the humidity inside its core for a long time. P. archon larvae dedicate a considerable amount of time to making the cocoon as well as to the preceding preparations. First, the larva has to bore a readily accessible tunnel that will allow the pupa to reach the outside after leaving the cocoon. Then it excavates a cavity where the cocoon will be made. Consequently, the cocoon will always be located near/on the surface of the trunk or leaf axillae, very well camouflaged, mainly, when on the trunk, underneath some layers of the fibre webs that surround it. The cavity where the cocoon stays is located at one end of the terminal larval gallery, whereas the other end often appears blocked by a false cocoon or compacted frass also built by the larva. In heavily infested palm trees it is possible to find several of these cocoons on the trunk, at close distance to each other, underneath the fibre webs. The cocoons are well sealed, excepting at the upper end where a very small and narrow exit can be seen; there, the palm fibres are brought together in such a way as to permit expansion by the pupa, pushing out head first, when leaving the cocoon on its way outside the palm, prior to adult emergence. After adult emergence, the cocoon keeps its former shape and volume and, should the pupal exuvia not be partly anchored on it, it is difficult to tell at first sight whether it is a live or empty one.

Most of the abdominal segments of the pupa are furnished dorsally with transversal rows of short spines pointing backwards. When ready to leave the cocoon, prior to adult emergence, the pupa lifts itself up by means of these spines and considerable mobility of the abdomen (which moves in a rotating manner), pushing against the fibres placed at the tapering top of the cocoon, loosening them and so exiting from the cocoon. If the cocoon is placed in such a way that its top just reaches the palm surface (the most common situation), when the pupa is about two thirds protruding from the cocoon, the adult starts to emerge; in such a case the pupal exuviae will be found anchored in the cocoon. However, should the cocoon be located a bit more inside the palm, the pupa comes out from it completely and then moves along the passage previously built by the larva towards the exit hole, where adult emergence will take place; in such a case, the pupal exuviae will be found either anchored in the exit hole, more or less half protruding, or free on the ground just below it (from Sarto I Monteys & Aguilar, 2005). P. archon adults are day flying insects, and fly in hot, sunny weather. As soon as they are ready to fly, they do so energetically (specially the males); they remain inactive when cloudy or rainy conditions prevail. Drescher & Jaubert (2003), using insect-proof tents, reported their peak of flying activity as being between 11:00 and 17:00; Delle-Vedove et al. (2012) indicated between 11:00 and 16:00. They do not feed as adults. In insectaria females live an average of 14.11 days (n=9; sample range: 7-25) whereas males live 23.83 days (n=6; sample range: 18-37); therefore, male life span seems to be about 70% longer than that of the female (Sarto I Monteys & Aguilar, 2005). Delle-Vedove et al. (2012) reported that 73% of the individuals they studied were sexually mature three hours after adult emergence, that mating peaked between 14:00 h and 15:00 h and 87% of the females were fertilized and started laying eggs 1.25 (± 1.14) days after mating. Females were generally monandrous, but nevertheless remained attractive after mating. P. archon males are very territorial. Their flight is very powerful, rapid and darting (an estimation would be 20 m/sec), being able to hover for a few seconds; the flight path is generally straight although right/left shifts are frequent and the moth can be seen balancing its body accordingly. They fly over and over rather small areas, returning to the same perching places. Their orientation skills are extraordinary, being capable of flying hundreds of meters, disappearing from human sight for several minutes and coming back exactly to the same palm leaf they had taken off from. Males usually perch on palm leaves or cut rachises around the trunk close to the crown (Fig. 7). When they see a flying object close to their own size, not necessarily conspecific, they immediately take off towards it. When reaching it, if not conspecific, they quickly fly back to the perching spot. However, if conspecific, a pursuit begins. Males follow either other males or females; groups of generally two adults can be seen together "pursuing" each other. However, should such flying pair cross the territory of another male, this third one would immediately join the pursuit so that the flying group would now be of three, or even four, if a fourth male joins. While the pursuit is on, they keep a distance of about 10 to 100 cm among them; no collisions have been observed. It looks like as if they wanted to show to each other their flying power and skill. This intense flight, though, is short-lived, as they are continuously changing direction, and even also changing pursuer; it reaches a height of about two meters above the palm crowns, generally not higher, maybe because they do not like to get too far away from the palms or simply because they feel less secure in the open air. These pursuits seemed to be somewhat different should the intruder be a female; in such cases, the pursuing flight looked slower than that described above (see below). When one of the males abandons the pursuit, whatever the reason might be, it flies back, now calmly and slowly, on a low flight (about 1.5 m above the ground, underneath the leaves of the row-lined palms), to the former perching spot, where it rests waiting for another intruder to come by.

Figure 7: Male perching alert on a palm leaf ready to take off. (Mâle en alerte perché sur une feuille de palmier prêt à décoller.)

A recent study showed that P. archon has a butterfly-like mating behaviour, i.e. that visual cues -and not female-released long-range pheromones- are the only ones used for mate location. It also showed that the morphology and fine structure of the antennae of this moth are strikingly similar to those of butterflies, with male sensilla apparently not suited to detect female-released long range pheromones. Despite intensive testing no female

pheromones to attract males could be found in P. archon. Instead males may release a pheromone at short distance, putatively a mixture of Z,E-farnesal, E,E-farnesal, and (E,Z)-2,13-octadecadienol; such a pheromone is released from the proximal halves of male forewings and hindwings. The outlined behaviour, long thought to be unique to butterflies, is likely to be widespread in Castniidae implying a novel, unparalleled butterfly-like reproductive behavior in moths (Sarto I Monteys et al., 2012). The courtship of P. archon is made up of six consecutive steps. They were singled out through the observation of four successful courtships as follows: 1. Localization/pursuit. The territorial male, who is perching or patrolling, first locates and approaches an intruder, energically flying toward it. If the latter is a conspecific female, the pursuit that follows is slower than that resulting from the intrusion of a conspecific male. The pair flies together along the palm rows, close to each other (about 10-15 cm), at heights very close to the palm crowns (1.5-2.0m in the experimental plot). During this phase, apart from visual stimuli, it is likely the female (and also a conspecific male intruder when encountered) receives the presumptive male sex pheromone at close range. 2. Alighting. Then, the pair alights, led by the female, on upright surfaces (a palm leaf or crown, the sides of a mesh tent), facing up. The female may walk shortly until reaching a spot where she can rest comfortably, folding her wings in the common noctuoid position, and staying still for the rest of the courtship. 3. Orientation. The male, who alighted a few centimeters below the female and has been closely following her movements, also has his wings folded, and moves up toward her, either on the female’s right or left side, at a small angle (40-50º) with her. There is no male flickering (i.e. a rapid sequence of opening and closing wings) (Fig. 8).

Figure 8: P. archon courtship. Male approaching the female from below. (Parade nuptiale de P. archon. Mâle approchant la femelle par le bas)

4. Thrusting. While approaching the female from below, the male touches the edges of her wings with his head/antennae, sometimes briefly inserting them under her wings. Also, his antennae and/or legs may also make contact with the side of the female. During this phase both sexes keep their wings fully closed. 5. Attempting. While approaching the male curls his abdomen and opens his clasping genital valvae in order to contact and grasp the female copulatory orifice to accomplish the copula. 6. Copulation. While in copula both sexes stay motionless, facing up, side by side, the male obviously lower than the female. This copula position is not the typical of Lepidoptera, since generally, after accomplishing the copula, the sexes position themselves on a straight line with their heads at opposite ends. The copulations observed lasted from 24 to 45 min, averaging 37.9 min (n=4) (Fig. 9). (from Sarto I Monteys et al., 2012).

Figure 9: P. archon pair in copula. Female above, male below. (Couple de P. archon en copulation. Femelle en haut, mâle en bas)

HOST PLANTS

P. archon larvae seem to be specialized feeders on Arecaceae (palm trees) as all reported foodplants fall within this monocotyledonous family; however, within it, the larvae are very catholic feeders, given the variety of genera they attack.

So far, in the Neotropics, the following palm species have been reported as foodplants for P. archon (all data based on larvae/cocoons actually found on the palms): At Paysandú (western Uruguay) on P canariensis (Houlbert, 1918), P. canariensis and Trithrinax campestris (Burmeist.) Drude & Griseb. (Bourquin, 1930), P. canariensis, T. campestris, Butia yatay Becc., C. humilis and Livistona chinensis (Jacq.) R.Br. ex Mart. (the latter quoted as “Latanias”) (Bourquin, 1933). In the Brazilian state of Rio Grande do Sul, Biezanko (1961) reported Syagrus romanzoffiana (Chamisso) Glassman, P. canariensis and L. chinensis; the same three palms were also mentioned by Ruffinelli (1967) from neighbouring Uruguay, although most likely he just used Biezanko's data. In northern Argentina, Varga (pers. comm.) indicated that, in the Province of Buenos Aires, at least the following palm species are affected: P. canariensis, T. campestris, B. yatay (the most affected) and Butia capitata Becc. (the least affected) (Sarto I Monteys & Aguilar, 2005). In Europe Drescher & Jaubert (2003) listed 21 palm species, belonging to 9 genera, on which P. archon damage had been noticed in Southeastern France: Brahea spp.: B. armata S Watson and B. edulis H.Wendl. ex S.Watson; B. capitata; C. humilis; Livistona spp.: L. australis (R.Br.) Mart., L. chinensis (Jacq.) R.Br. ex Mart., L. decipiens Becc. ex Chabaud and L. saribus (Lour.) Merr. ex A.Chev., Phoenix spp.: P. canariensis, P. dactylifera L., P. reclinata Jacq., P. roebelenii O'Brien and P. sylvestris (L.) Roxb.; Sabal spp.: S. mexicana L.H. Bailey, S. minor Pers. and S. palmetto (Walter) Lodd. ex Schult. & Schult.f.; Trachycarpus spp.: T. fortunei, T. wagnerianus hort. ex Becc. and T. campestris; and Washingtonia spp.: W. filifera and W. robusta H. Wendl. To the previous list, S. romanzoffiana was added by the Conselleria de Agricultura, Pesca y Alimentación of the Generalitat Valenciana (Spain) (Anonymous, [2003]).

SYMPTOMS AND DAMAGES

Apart from actually finding remains of several P. archon life stages on the palm (hatched/live eggs near/on the crown, cocoons and pupal exuviae located on/protruding from the trunk and/or crown (Fig. 10), the latter sometimes also found on the ground), which undoubtedly indicates it has been or it is being infested by the castniid, there are some symptoms seen on palms that might also indicate infestation. Figure 10: P. archon pupal exuviae (red arrows) on T. fortunei palm trunk. (Exuvies de chrysalides vides de P. archon (flèches rouges) sur tronc de T.

fortunei)

The latter symptoms are shown in Figure 11a-f: (1) Fig. 11a. Presence of sawdust on the palm crown and/or trunk (Présence de sciure sur la couronne et/ou le tronc du palmier) (2) Fig. 11b. Presence of perforated or nibbled leaves; non specific (Présence de feuilles perforées ou grignotées ; non spécifique) (3) Fig. 11c. Presence of gallery holes (axial and transversal) within the trunk observable when the trunk is cut in slices (Présence de trous de galeries (axiales et transversales) dans le tronc observable lorsque le tronc est découpé en tranches). (4) Fig. 11d. Abnormal development of axillary leaf buds (Développement anormal des bourgeons axillaires)

(5) Fig. 11e. Deformation and abnormal twisting of palm trunks (Déformation et torsion anormale du tronc).

(6) Fig. 11f. Abnormal drying up of the palms, specially the core leaves. (Dessèchement

anormal des palmiers, en particulier des feuilles centrales)

Fig. 11a Fig. 11b

Fig. 11c Fig. 11d

Infested trunks may be severely damaged because of the galleries produced by the larvae as they bore through them, as well as by secondary infections by fungi and other microorganisms that may result. Heavy larval attack may kill the palm tree (Fig. 12).

Fig. 11e Fig. 11f Fig. 11f

Figure 12: Left: Dead T. fortunei palm because of heavy P. archon larval attack. Right: Palm nursery (T. fortunei) heavily attacked by P. archon larvae showing some dead palms.

(À gauche : T. fortunei mort en raison d’une forte attaque de larves de P. archon. À droite : Pépinière des palmiers T. fortunei fortement attaquée par des larves de P. archon avec des palmiers morts)

Some of those symptoms differ a little amongst palm species. For instance, infested palmate-leaved palms, such as Trachycarpus, Chamaerops, Washingtonia, Trithrinax, would show, on the fully developed leaf (pierced when young by early instar larvae), a series of consecutive perforations on a circular sector; also, larval galleries will only appear in the trunk, not in leaf rachises. On the other hand, pinnate-leaved palms, such as Phoenix, would show scattered perforations on the leaves and larval galleries will appear in the trunk as well as in leaf rachises. In the Mediterranean region there are other native lepidopterans attacking graminaceous crops which have been occasionally observed by us boring palm trees (P. canariensis, T. fortunei), mostly the tender growing point, therefore producing perforations on the leaves similar to those described for P. archon. These are the European corn borer, Ostrinia nubilalis (Hübner, 1796) (Crambidae) and the Mediterranean corn stalk borer, Sesamia nonagrioides (Lefèbvre, 1827) (Noctuidae), both well known stem-borers of corn (Zea mays Linnaeus, 1753; Poaceae); the damage their larvae produce on palms is generally unimportant unless they attack young palms in nurseries where some might die (from Sarto I Monteys & Aguilar, 2005).

ACKNOWLEDGEMENTS Mr Lluís Aguilar from the Servei de Sanitat Vegetal, Generalitat de Catalunya, has kindly provided the following images: Fig. 4 (Left), Fig. 8, Fig. 10, Fig. 11a, 11d, 11e, 11f.

REFERENCES

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