A practical method for predicting the short-time trend of bivoltine populations of Ips typographus (L.) (Col., Scolytidae)

Ips typographus is the main spruce pest of European forests. In most areas of the Italian Alps there are two generations per year; overwintering adults fly in May looking for trees suitable for breeding, their offspring emerge in summer, 7-8 weeks after tree colonization, and the adults of the second generation emerge in spring of the following year after overwintering under the bark or in the litter. A long-term population monitoring was carried out in north-east Italy with the aim at developing a prediction model able to estimate the population density of the following year. Between 1996 and 2004, pheromone traps monitored populations of I. typographus annually. Monitoring lasted 4 months (May-August), with replacement of pheromone dispensers after 8 weeks. Insects trapped before dispenser change were called 'spring captures' (May-June), and included both overwintering and re-emerging adults. Beetles caught after dispenser change were called 'summer captures' (July-August), and inclu...