The palm borer (Paysandisia archon) is native to South America and recently made its alarming entry into Southern Europe. The adult moths are beautiful and impressively large, but their horrendous larvae cause fatal damage to palm trees.
Besides the observation of the remarkable adult palm borers, feeding damage caused by the larvae can easily be recognized. Generally sawdust is found in the palm crown or on the stem. The leaves are chewed and show perforations. Galleries are formed inside the stem. Moreover an aberrant development of leaf buds can be observed, as well as turned stems. Affected palm trees dry out and soon wilt.
The adults have a wingspan of approximately the size of a human hand. The forewings are greenish brown with brown streaking and the hind-wings are orange-red with a bold black horizontal stripe interrupted by 6 white spots. Females have a prominent ovipositor. Eggs are oblong and rose-brown. They are approximately 5 mm long. Larvae look like rose-white grubs with a brown head shield. An adult larva is on average 9 cm long. Before larvae pupate, they make an oblong cocoon out of palm tree fibers. These cocoons measure about 6 cm long. Pupae are red-brown and around 5 cm long. The palm borer moths are active during summer time. Eggs are deposited on palm fibers close to the crown. A female deposits around 140 eggs. The larvae hatch after 2-3 weeks. On their search for food and shelter, they bore into the trunk. The palm borer overwinters as larva, sometimes twice, and, as result the larval stage can have a one-year cycle or a two-year cycle. The pre-pupa stage lasts approximately 2.5 weeks. In this stage the cocoon is generated. The pupal stage lasts 1.5 to 2.5 months, depending on the period in which cocoons were formed, respectively half July and half March. The total life cycle is more or less 13 months for a one-year cycle and 23 months in case of a two-year cycle.