The increase of temperature observed in the last decades in the range of the processionary moth may have promoted the spread of the insect, as its survival during winter largely depends on the temperature. Simultaneously, an expansion of the outbreak area at upper elevation/latitude has been detected, affecting also pine species which were previously little concerned (Scots and mountain pine) (Benigni and Battisti, 1999; Goussard et al., 1999).
 
 
 

However, it is not clear if the expansion of the outbreak area is directly related to temperature or if other factors such as the distribution of the host plants and of natural enemies are involved. Extended diapause appears to be a key adaptation for survival under extreme conditions, as it allows the spreading of the individuals originated from one colony over several years. This fact will increase consistently the probability of survival for the colony.

 

Egg cluster on Pinus sylvestris at Mt. Avic, Aosta Valley, July 2001, 1350 m a.s.l.

 
 
 
The pine processionary moth may attack all species of pines (Pinus) and cedars (Cedrus) in whatever growing condition (forest, ornamentals, gardens). Preferences for a given host have been described from field observations but they need an experimental confirmation. Surprisingly, exotic hosts such as the Monterey pine (Pinus radiata) are more severely infested when growing mixed with other hosts. The result of the attack depends on the host preference at egg laying and on the larval performance thereafter. The two variables will be experimentally assessed in the Promoth project, with special attention to the new hosts which the insect may encounter in the expansion areas.