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Use of entomopathogenic nematodes for the control of Paysandisia archon Burmeister

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Abstract

A preventative and a curative field trial were carried out in 2008 on in-ground and potted Trachycarpus fortunei (Hooker) Wendland palms in order to evaluate the efficacy of two different formulations of the entomopathogenic nematode Steinernema carpocapsae (Weiser) in respectively preventing new Paysandisia archon Burmeister infestations and controlling the palm pest on already infested plants. The tested S. carpocapsae formulations showed very high efficacy (close to 100%) in both preventing new infestations and controlling P. archon. The entomopathogenic nematode can thus be considered a highly valuable tool for the control of this target pest.
Insect Pathogens and Insect Parasitic Nematodes
IOBC/wprs Bulletin Vol. 45, 2009
pp. 375-378
375
Use of entomopathogenic nematodes for the control of Paysandisia
archon Burmeister
Sandro Nardi1, Emanuela Ricci1, Roberto Lozzi1, Francesco Marozzi1, Edith Ladurner2,
Federico Chiabrando3, Nunzio Isidoro4 & Paola Riolo4
1Servizio Fitosanitario Regionale, Agenzia Servizi Settore Agroalimentare delle Marche, Via
Alpi 21, 60131 Ancona, Italy; 2Intrachem Bio Italia, via Calcinaro 2085 int. 7, 47023 Cesena
(FC), Italy; 3Bioplanet, Via Masiera Prima 1195, 47023 Martorano di Cesena (FC), Italy;
4Dipartimento di Scienze Ambientali e delle Produzioni Vegetali, Università Politecnica delle
Marche, Via Brecce Bianche, 60131 Ancona, Italy
Abstract: A preventative and a curative field trial were carried out in 2008 on in-ground and potted
Trachycarpus fortunei (Hooker) Wendland palms in order to evaluate the efficacy of two different
formulations of the entomopathogenic nematode Steinernema carpocapsae (Weiser) in respectively
preventing new Paysandisia archon Burmeister infestations and controlling the palm pest on already
infested plants. The tested S. carpocapsae formulations showed very high efficacy (close to 100%) in
both preventing new infestations and controlling P. archon. The entomopathogenic nematode can thus
be considered a highly valuable tool for the control of this target pest.
Key words: Paysandisia archon, palms, entomopathogenic nematodes, biological control
Introduction
The South American palm borer Paysandisia archon Burmeister (Lepidoptera: Castniidae) is
native to Uruguay and central Argentina. It has been accidentally introduced to Europe, where
it is spreading rapidly. In the EPPO (European and Mediterranean Plant Protection
Organization) region it was first found in 2001 in Spain and France. The presence of P.
archon has been reported in Spain, France, UK, Greece and Italy, where the moth is present
in the following regions: Campania, Marche, Tuscany, Sicily, Apulia, Liguria, Emilia
Romagna, Abruzzo and Lazio (OEPP/EPPO, 2008; Nardi et al., pers. comm.). The moth is
currently listed in EPPO A2 List of “Pests recommended for regulation as quarantine pests”.
P. archon lives on a wide range of palms (Arecacae family). Most common infestation
symptoms of the pest on palms are: Presence of debris (fibrous material) discarded by the
boring larvae on top of the stem close to the crown, wilting and chlorosis of the crown, pupal
exuviae visible outside on the stem, galleries along the longitudinal axis of the leaf petiole,
presence of perforated or nibbled leaves and eventually perishing of the palm.
In the Marche region, located in central-eastern Italy, ornamental palm species are not
only an extremely important part of the landscape, but also of high economic importance,
because many nurseries are specialized in their commercial cultivation.
In the Marche, almost all common palm species are susceptible to P. archon attack, but
the most severe infestations occur on Chamaerops humilis Linnaeus and Trachycarpus
fortunei (Hooker) Wendland. In this region P. archon probably has one generation per year,
but the occurrence of different larval instars throughout winter and spring suggests that a
small part of the moth population may have one generation every two years (Riolo et al.,
2005).
376
The Marche Plant Protection Service, over a period of three years (2005-2007), carried out
several trials with chemical insecticides to prevent the spread of P. archon and to limit
damage on palms (unpublished data). Both foliar and soil applications of different products
were tested. Foliar chemical insecticide applications showed difficulties in reaching
endophagous P. archon larvae and preventative treatments proved to be more effective than
curative treatments. Given these results and those obtained in previous preliminary studies
with entomopathogenic nematodes (henceforth EPNs) (Sanches & Clemente, 2007), in 2008
we decided to evaluate the efficacy of both preventative and curative applications of
Steinernema carpocapsae (Weiser) (Nematoda: Steinernematidae), mutualistically associated
with the bacterium Xenorhabdus nematophila (Enterobacteraceae), for the control of P.
archon.
Material and methods
Tested S.carpocapsae formulations
In both the preventative and the curative trial the following two formulations of S.
carpocapsae were tested: Nemasys C, produced by Becker Underwood (UK) and distribuited
in Italy by Intrachem Bio Italia S.p.A. and Nemopak SC Palme, produced by Idebio S.L.
(Spain) and distribuited in Italy by Bioplanet s.c.a.. As recommended by the producer, at the
moment of the application, a liquid chitosan-based adjuvant (a.i. N-acetyl-glucosamine) was
added to the Nemopak SC Palme tank mixture at a rate of 10 ml/106 EPNs, while no adjuvant
was added to Nemasys C.
Preventative trial
The trial was carried out in a palm nursery in Massignano (AP, Italy) in July-October 2008,
where the target pest was present for several years. Prior to beginning of the trial the mean
palm infestation level, assessed on a sample of 100 randomly selected plants, was 9%.
Sixty two-year old uninfested T. fortunei palms were transplanted into the ground in the
study area just prior to the beginning of the trial. A randomized complete block design with
four replicates of 5 plants per plot was used to evaluate the efficacy of the two S. carpocapsae
formulations in preventing P. archon infestations. An untreated control treatment was also
included. All treatments were applied three times (July 3, July 24, and August 28) during the
flight period of ovipositing P. archon females. In the successive applications, according to
the recommendations of the distributors, Nemasys C was used at a rate of 6.3x106, 6.6x106,
and 6.8x106 ENPs/plant (spray volume: respectively 0.63, 0.66, and 0.68 l/plant), while
Nemopak SC Palme was used at a rate of 7.4x106 EPNs/plant (spray volume: 0.5 l/plant). To
exclude the possible influence of water on new P. archon infestations, every time EPNs
sprays were applied to the treated plots, the plants of the untreated control were sprayed with
0.5 l/plant of water only.
In order to determine the percentage of new P. archon infestations, all plots were
checked for infestation symptoms at 20 day intervals throughout the study period and 20 days
after the last treatment application (intermediate assessments). The final assessment was
performed at the end of October.
Curative trial
The trial was carried out in a palm nursery in Grottammare (AP) in October 2008 on 2-3-year
old potted T. fortunei plants, which all showed obvious signs of P. archon infestation. A
randomized complete block design with 4 replicates of 5 plants per treatment was used. The
products were applied to the treated plots on October 2. According to the recommendations of
377
the distributors, Nemasys C was applied at a rate of 8x106 ENPs/plant (spray volume: 0.8
l/plant), and Nemopak SC palme at 10x106 ENPs/plant (spray volume: 1 l/plant). To exclude
the possible influence of water on P. archon mortality, untreated control plots were treated
with 1 l/plant of water only.
Twenty days after the treatment applications, all palms were dissected, and the number of
living and dead P. archon specimens per plot was recorded. To verify whether the EPN was
the cause of the death, dead specimens were brought to the laboratory, dissected and observed
under the microscope to detect the ENPs. For each plot percent mortality due to ENPs was
calculated.
Statistical analysis
The percentage of new P. archon infestations (preventative trial) and the percentage of
mortality due to EPNs (curative trial) were compared across treatments using 1-way ANOVA,
followed by Tukey’s test for post-hoc comparison of means. To improve homoscedasticity, data
were arc sin square root (x/100)-transformed.
Results and discussion
Preventative trial
Throughout the study period and at the final assessment no new P. archon infestations were
observed in the treated plots. Both S. carpocapsae-based products were highly effective in
preventing new infestations. Differences among treated plots failed significance (1-way
ANOVA: F(2, 9)=1.00; P=0.41) (Table 1), because also in the untreated control the infestation
level at the final assessment was extremely low (5.0 %). However, the mean infestation level
in the nursery had increased from 9% at the beginning of the trial to 27%. Low infestation
levels in untreated control plots have been observed in other preventative small-plot trials in
the Marche region (unpublished data). This may be due to the behaviour of the target pest: P.
archon females apparently prefer to colonize already infested palms and those located in their
immediate surroundings prior to moving to plants which are farther away (Sarto et al., 2005).
Table 1. Percentage of new P. archon infestations (m±s.d.) in the different treatments at the final
assessment. Different letters indicate statistically significant differences (Tukey’s test: P<0.05).
No. Treatment New P.archon infestations (%)
1 Nemasys C 0.0±0.0 a
2 Nemopak SC Palme 0.0±0.0 a
3 Control 0.5±10.0 a
Curative trial
In the curative trial highly significant differences among treatments emerged (1-way
ANOVA: F(2, 9)=142.51; P<0.0001). Both S. carpocapsae-based treatments were highly
effective in controlling P. archon infestations (Table 2). All P. archon specimens found inside
palms were in the larval stage, and observations under the microscope confirmed that dead
larvae had been infested by EPNs.
378
In the Nemopak SC Palme-treated plots (applied rate: 10x106 EPNs/plant), a mean
number of 6.5±1.3 P. archon larvae was retrieved from the palms, and mortality due to S.
carpocapsae was 100% in all plots. In the Nemasys C-treated plots (applied rate: 8x106
EPNs/plant), the infestation level was slightly higher than in the other treatments (mean no.
larvae: 11.8±4.6), and mortality due to EPNs was slightly, though not significantly lower
(94.5%; 100% in 3 out of 4 plots). No dead P. archon larvae were found in the untreated control
plots (mean no. larvae: 9.0±4.3), confirming the absence of natural antagonists and/or other
abiotic factors, which may limit the spread of the pest in the Marche region.
Table 2. Number of living and dead P. archon larvae (m±s.d.) and mortality due to EPNs in the
different treatments. Different letters indicate statistically significant differences (Tukey’s test:
P<0.05).
No. Treatment No. living
larvae
No. dead
larvae
Mortality due to
EPNs (%)
1 Nemasys C 1.0±2.0 10.8±3.3 94.1±11.8 b
2 Nemopak SC Palme 0.0±0.0 6.5±1.3 100.0±0.0 b
3 Control 9.0±4.3 0.0±0.0 0.0±0.0 a
Our results confirm the preliminary results obtained by Sanchez & Clemente (2007). Irrespective
of the tested formulation,, S. carpocapsae proved to be highly effective in both preventing new
infestations of P. archon and limiting the spread of the pest via curative treatments. EPNs are
safe for non-target vertebrates and arthropods and the environment and thus offer an interesting
alternative to chemical insecticides, especially in public areas. S. carpocapsae can be considered
a valuable tool for the control of endophagous P. archon larvae.
Acknowledgements
We thank Alfredo Piunti for his help in organizing the trials.
References
OEPP/EPPO 2008: Paysandisia archon. OEPP/EPPO Bulletin 38: 163-166.
Riolo, P., Isidoro, N., Nardi, S. 2005: Prime osservazioni sul ciclo biologico di Paysandisia
archon (Lepidoptera, Castniidae) nelle Marche. Incontri Fitoiatrici, Difesa delle Colture
Ortoflorofrutticole, 24-25 febbraio 2005: 82-83.
Sanchez, A.S. & Clemente M.D. 2007: Incidencia de Paysandisia archon (Burmeister, 1880) en
EspaĖa (Comunidad Valenciana). Medidas de control biologico. Available on line at:
http://www.sanremopalme.it/it/risorse/documento.php?d=33.
Sarto i Monteys, V. & Aguilar, L. 2005: The Castniid Palm Borer, Paysandisia archon (Bur-
meister, 1880) in Europe: comparative biology, pest status and possible control methods
(Lepidoptera: Castniidae). Nachrichten des Entomologischen Vereins Apollo, N.F. 26 (1/2):
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Larvae are endophagous; cannibalistic (even affecting prepupal larvae within their fully formed cocoons), mostly as a result of territoriality; undergo unusual lethargic periods and make "false cocoons", most likely to confuse predators/parasitoids; generally go through nine instars (occasionally seven or eight), increasing dramatically in size (from ca. 0.7 cm to 9 cm), and in so doing have considerable destructive power. The total larval stage is quite long, ca. 10.5 months in larvae having a one-year cycle and ca. 18.5 months in larvae having an almost two-year cycle. Larvae can be found tunnelling in different parts of the palms, which largely depends on the larval size, although always on/near the top (crown) of the palm; they will normally not abandon their palm host until the adult stage is reached. The prepupal larval stage is long and 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 includes the time spent by the larva inside the cocoon before converting into pupa; this time is around 17 d in early spring although it can be shortened to only 9 d in early summer. The cocoons (av. length 5.8 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. Pupae formed in the second half of March took an average of 66 d to complete their metamorphosis to adults; those formed in the first half of April took 52 d; those formed in the first half of July took 43 d. The adult moths are day-flying insects. ♂♂ (which occur slightly less abun-dant than ♀♀, in the ratio of 1:1.19) are very territorial and fly in hot, sunny weather. Their flight is very powerful, rapid and darting (an estimation would be 20 m/s), 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. In the lab, ♀♀ lived an average of 14.1 d whereas ♂♂ lived 23.8 d, and both sexes do not appear to feed at all in this stage. Preliminary research indicates that sex recognition seems to be visual at first. ♀♀ simply move around within the appropriate habitat until they are spotted by a patrolling ♂, in much the same way as butterflies do. The fact that electroantennograms carried out using ♀ ovipositor (hexane) extracts, triggered a positive and significant response in ♂ antennae, seems to indicate that P. archon has at least a ♀-released short-range pheromone for conspecific sex recognition, while ♀-released long-range pheromone, i.e. that used by other heterocerans to attract conspecific ♂♂ at longer distances, might be absent in P. archon and replaced by visual attraction. Mating in the wild has been observed and described for the first time. ♀♀ lay eggs singly (through their long extensible ovipositor) in a very quick and inconspicuous manner; most eggs are found within the fibre webs closest to or within the palm crowns; they are not glued to the fibres, remaining loose within their thick layers (1–2 cm inside). Dissected virgin ♀♀, known to have laid no eggs, were found to have about 140 eggs. As for the life cycle, adults appear in the wild in mid-May and disappear in late September, with a peak during June and July; sightings of adults in May, August and September are much rarer. Live eggs are expected to be found from late May to mid-October. 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, although a second group will experience an almost two-year one. Live cocoons can be found from mid-March to mid-September. In summary, the P. archon life cycle in Catalonia 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. P. archon larvae seem to be specialized feeders on Arecaceae (palm trees) as all reported hostplants fall within this monocotyledonous family; however, within it, the larvae are unspecified feeders, given the variety of genera they attack. As to natural enemies, in Europe as well as in the Neotropics, there are no factual data as yet; however some empty eggs have been found in the wild in Catalonia strongly suggesting the attack by a hymenopterous egg parasitoid or an egg-predacious hemipteran. Very cold winter temperatures lasting for several consecutive days might increase mortality in the overwintering archon larval population sheltered in palm trees; notwithstanding that, this pest has proven to be well adapted to the Mediterranean climate. Symptoms of infestation by P. archon on palms are (1) presence of sawdust on the palm crown and/or palm trunk; (2) presence of perforated or nibbled leaves (non specific); (3) presence of gallery holes (axial and transversal) within the palm trunk (observable when the palm trunk is cut in slices); (4) abnormal development of axillary leaf buds; (5) deformation and abnormal twisting of palm trunks; (6) abnormal drying up of the palms, especially the core leaves. As for possible measures of control, so far, only those using chemical insecticides have been tested (apart from pulling-up and burning the infested palms); good results were obtained by wetting the palm crown and trunk with contact and/or systemic organophosphorus insecticides (Chlorpyrifos, Acephate and Dimethoate); best results were obtained by using Chlorpyrifos 48%, dose 200 ml/Hl or Acephate 75%, dose 150 g/Hl.
Prime osservazioni sul ciclo biologico di Paysandisia archon (Lepidoptera, Castniidae) nelle Marche
  • P Riolo
  • N Isidoro
  • S Nardi
Riolo, P., Isidoro, N., Nardi, S. 2005: Prime osservazioni sul ciclo biologico di Paysandisia archon (Lepidoptera, Castniidae) nelle Marche. Incontri Fitoiatrici, Difesa delle Colture Ortoflorofrutticole, 24-25 febbraio 2005: 82-83.
Incidencia de Paysandisia archon (Burmeister, 1880) en Espaa (Comunidad Valenciana) Medidas de control biologico Available on line at
  • A S Sanchez
  • M D Clemente
Sanchez, A.S. & Clemente M.D. 2007: Incidencia de Paysandisia archon (Burmeister, 1880) en Espaa (Comunidad Valenciana). Medidas de control biologico. Available on line at: http://www.sanremopalme.it/it/risorse/documento.php?d=33.
  • Oepp Eppo
OEPP/EPPO 2008: Paysandisia archon. OEPP/EPPO Bulletin 38: 163-166.