"Ask the Expert" covered some of the points earlier this year and I attach the question and answer. Of course the problem is dynamic and continuing to evolve. We could use the Forum to create a data base for these two pests.
Question - "This year we noticed a very beautiful moth in our garden in the Languedoc Roussillon part of France and took some pictures of it. I wonder if you know this moth? I understand that it comes originally from South America and that it is harmful to palm trees."
Read the answer.
Answer (December 2009) - "This is a photograph of Paysandisia archon, a moth belonging to the Castniidae family with a palm-boring caterpillar. It is a native pest of Argentina and Uruguay and was first recorded in France in 1999, in Spain in 2001 and in Mallorca in 2003. It is now recorded throughout the Mediterranean Basin including in France, Italy, Spain and the Balearic islands. Its larvae attack many palms, but prefer - in order - Chamaerops humilis, Phoenix canariensis, Trachycarpus fortunei and Washingtonia spp.
At home the Paysandisia archon larva infests palm trees but it is kept in check by natural predators and parasites. It appears to have been brought to Europe accidentally on imported palms which are now being planted by many municipalities throughout the Mediterranean Basin to replace the existing plane trees, many of which are old and diseased.
The beautiful moth is large, some 90-110mm across, with dark green front wings with brown streaking, and bright red back wings with bold black and white markings. The adults fly during the day from May to September. Eggs are laid in the palm crowns where the grubs hatch. The caterpillar first eats tender leaves at the heart and then bores into the trunk during a period of one to two years.The first sign of attack is a very regular series of holes in the emerging fronds. Later, there will be piles of sawdust mixed with excrement at the base of the fronds and finally, after pruning, holes and even cocoons will be seen in the base. The grub will over-winter and will stay in the larval stage for up to 18 months. Without control the plant will eventually wilt and die.
Detection and control are difficult as larvae cannot be seen or reached easily within the crown. Periodic inspections will reveal any damage in the emerging young fronds. Chamaerops humilis is especially vulnerable as its heart is so small. Since this moth is not a pest in its native country no control method has yet been developed. It is believed that the moth could spread to a much larger region in the future if measures are not taken; however, natural predators may also be introduced with the imported palms.
A good soaking of the heart with an insecticide containing chlorpyriphos and dimethoate should be effective; this is not a general recommendation, however, and appropriate authorities should be contacted before any attempt is made to spray these pests.
In Nîmes, specimen palms are covered with large plastic netting to prevent egg-laying but this does take away some of the beauty of the palm tree.
Rhynchophorus ferrugineus is another pest of imported palm trees. This is a member of the coleoptera originating in Asia and Malaysia which arrived in Spain in 1995 and was first detected in Mallorca in 2006. It attacks a great variety of palms, with a preference for Phoenix canariensis, Phoenix dactylifera, and Washingtonia spp.
The adult is 2-5cm long and 1 cm wide, coloured red, with black spots on the body, corrugated wing sheaths, and a long beak.
The first parts of the palm to be attacked are the most tender leaves at the heart and then the trunk. Usually the first sign of damage is the collapse of the central fronds, by which time the palm is moribund.
In view of the dangers posed by this pest and the absence to date of effective treatments, experiments are being carried out in many different areas of the Mediterranean, ranging from spraying regularly through the summer, through avoiding pruning except in the winter, to zapping the crown of an infected palm with a batch of microwave "ovens" mounted on extended forklifts.
Please see page 15 of TMG 56 for additional information"
