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"The thesis* is in response to strong demand " Laurence Ollivier**, a CIRAD researcher, points out "the part of the Mediterranean stretching from Spain to Italy is affected by this particularly invasive moth, which is now threatening date palm plantings in the Maghreb and developing countries. Laboratory trials have shown that the larvae love them …".

The insect originated in Argentina and western Uruguay, and its probably arrived with imported palms prior to the year 2000. Twenty palm species, including palms endemic to the South of France, are hosts and are now affected. Every summer, the insect invades new sites and becomes established. As soon as they hatch, the young caterpillars colonize the heart of the palm and are impossible to detect as first glance. After almost a year's development, during which time they have caused rotting and leaf deformation that affect the palm's growth and survival, moths emerge from the stem. Severely affected palms can be infested by hundreds of caterpillars.
Urgent control measures

Conclusive trials–using a sticky substance–have been conducted by INRA on palms on the INRA-SupAgro campus in Montpellier and in the City of Montpellier, but the substance is not yet available on the market. The chemical pesticides currently used are not suited to these levels of infestation and cannot be considered a sustainable control method.

Laurence Ollivier's team is centring its research on biological control : finding natural enemies of the moth, for instance egg parasitoids. To this end, a field trip to Argentina/Uruguay, in the insect's area of origin, is required. In the immediate future, thanks to the City of Montpellier's parks and gardens services, which are providing infested stems, the team will be studying how the insect reproduces under natural conditions and in the laboratory. Plant-insect interactions will also be analysed; volatile compounds emitted by the palms may be a signal by which the moth recognizes potential hosts.

A trapping system for physical control of the moth is also being studied. The traps would contain a pheromone (a natural chemical molecule) and be hung in the palms to attract, trap and consequently eradicate adult insects without harming the environment, in urban and rural areas. With the support of the authorities, trapping campaigns could be conducted on palms once a pheromone has been identified. "One alternative could be to plant Mediterranean species such as tamarisks, plane trees, cypress trees, oleasters and pines ", adds Laurence Ollivier.

* Thesis entitled "Chemical mediation and the invasive process in a lepidopteran found on palms in Europe and the Paris region", specifically looking at the impact of a species of invasive insect on palm biodiversity and the role of chemical ecology in intra- and interspecific relations.

** Researcher with the Controlling Pests and Diseases in Tree Crops Internal Research Unit (UPR)