General
The South American palm borer (Paysandisia archon) belongs to the family of Castniidae. It is a neotropical species native to north-western Argentina, Brazil (Rio Grande do Sul), Paraguay (Paraguayan Chaco) and western Uruguay. It was accidentally introduced to Europe from Argentina, as larvae hidden in imported palm trees.
In Europe, the South American palm borer (Paysandisia archon) is an invasive species where it causes serious damage and mortality in palms. The South American palm borer (Paysandisia archon) is a powerful flyer. The pest is spread over large distances mainly through movement of infested plant material.
Life cycle and appearance of South American palm borer
The eggs of the South American palm borer (Paysandisia archon) are fusiform (tapering off at both ends), resembling rice grains. They have a light creamy or creamy pink colour when freshly laid, with six to seven ridges. Most eggs are found within the fibre webs closest to or within the palm crowns.
Immediately after hatching, the larva is pink. After the first moult, mobility diminishes considerably and the larva turns ivory white. There are nine larval instars. The larvae start feeding immediately after hatching and bore into the host plant.
The pupae are about 5.5 cm long and are pale yellowish immediately after pupation, then turn reddish brown within about two days. Most of the abdominal segments are furnished dorsally with transversal rows of short spines pointing backwards. The pupae are protected by a palm-fibre cocoon, which makes them very cryptic. The pupa exits the cocoon using its spines and the mobility of its abdomen. Pupal exuviae can be found anchored in the cocoon.
The adult is a large moth with a wingspan of 6 to 10 cm and has greenish-brown forewings. The hindwings are orange, with a wide transverse black band containing five or six white cells. The antennae are clubbed with a typical apical hook. Females bear a long, telescopic ovipositor and are generally larger than the males.
Damage symptoms
Larvae of the South American palm borer (Paysandisia archon) can be found tunnelling in different parts of the palms. Early-instar larvae can be found in the stipes (trunk), within the fruit, or within the leaf rachis. They may bore into the young, packed palm leaves. So, once the leaf develops, opens and expands, a series of consecutive holes on a circular section become visible. Large larvae will only be found in the stipe. They tend to bore into and remain within the very core of these structures, where the humidity is high and temperature fairly stable.
Damage symptoms depend on the palm species and include abundant sawdust, extruding from larval galleries on the crown and/or stipe; perforated or nibbled leaves; gallery holes within the trunk and leaf petioles; deformation and abnormal twisting of stipes; abnormal drying up of the palm, especially of the core leaves. Heavy larval attack may kill the palm tree.