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Classification and host plants
Species: P. archon Burm.
“Phytopathology, agricultural entomology and applied biology” – M.Ferrari, E.Marcon, A.Menta; School edagricole - RCS Libri spa
Host plants: in Italy it mainly infests Chamaerops humilis and Trachycarpus fortunei, specimens of Phoenix canariensis are secondarily infested. Castnid is less frequent on other palm species.
Paysandisia archon is an insect that, coming from Argentina and Uruguay, arrived in Europe thanks to the trade of palm trees (Trithinax sp.) And for some years has also been present in Italy.
The Paysandisia archon is a large butterfly that reaches 9-11 cm with open wings.
Identification and damage
The damage can be significant on Chamaerops and Trachycarpus because particularly serious infestations also lead to the death of all the jambs of a plant. When infesting the Phoenix canariensis, the caterpillars dig tunnels of about 60 cm. long, without compromising its vitality if the plants are adults. These tunnels are rather free from excavation and feeding residues that the larvae unload outside through special openings.
In adults, the front wings are olive brown while the rear ones are red with irregular white and black spots and due to the considerable size, during the flight, the flapping of the wings is distinctly audible.
The eggs are laid isolated on the leaves or on the jambs (the unbranched stem with a rosette of leaves at the apex -Palms-), sometimes some eggs are laid close together, very rarely in contact.
The larvae of this insect feed on the plant tissues of the palms by digging tunnels inside the stem and leaf stalks, from which dark brown color emerges. The caterpillars live by opening the way between the bases of the leaf stalks of Chamaerops and Trachycarpus and, possibly, by digging short tunnels in the jambs.
Caterpillars, especially during the last larval ages, dig their tunnels entering and leaving the host plant. Once mature, the larvae, starting from the mouth of a tunnel, cover a long stretch of silk and then weave a cocoon in the shelter of the plant.
The chrysalis, in the process of flickering, runs through the section covered with silk and reaches the outlet of the tunnel. After flickering, the exuviae (external coating of the insect which is replaced and abandoned following the moult) of the chrysalis remain for a long time on the plant and are useful for easily identifying the phytophagous (especially on the Phoenix canariensis).
Castnid of the palms - Paysandisia archon Burm. (photo www1.montpellier.inra.fr)
The fight against this insect is difficult, as the infestation is located within the palm or leaf stalk jambs, where insecticidal products have difficulty penetrating. Furthermore, there are currently no plant protection products registered against this adversity on the market, so that these interventions can only be carried out with PPOs (ornamental products).
Biological control methods are being studied based on the use of entomopathogenic nematodes, typically terrestrial organisms that actively move in search of host larvae to feed on, both preventive and curative confinality.
The eradication strategy that can be implemented at the moment is based on the demolition and destruction of the affected plant by means of suitable heat treatment or fine mechanical shredding, making sure that the materials obtained are obtained not to exceed 2 cm in size.
Anyone observing symptomatic plants or the presence of the insect in private gardens or urban green areas, must report it to the Municipality of residence and the Regional Phytosanitary Service of Lazio (Tel 0651684047 - 3659, fax0651686828, mail: [email protected]) , who will indicate the techniques and methods to be followed for eradication.