The outbreak of pine processionary moth in Venosta/vinschgau: ecological and economic aspects

A sudden outbreak and range expansion of the pine processionary moth Thaumatopoea pityocampa (Lepidoptera, Notodontidae) was reported in 1999-2005 for Venosta/Vinschgau, an area of northern Italy where the species generally occurs at low density. The forests of Pinus nigra (introduced) and Pinus sylvestris (native) were attacked on a total area of several hundred hectares, on the southern slope of the valley. Repeated applications of a biological insecticide based on Bacillus thuringiensis kurstaki were necessary to limit the population growth and the consequent damage to the trees and the environment. We used a combination of ecological and economic variables to make predictions about the outcome of the present and future outbreaks. The insect is well adapted to cope with the extreme conditions at its range edge, especially because of the possibility to enter extended diapause as a pupa in the soil. The presence of the insect in the pine forests threatens soil stability, landscape value, and tourism use of the area because of the allergenic hairs released by the caterpillars. The high persistence capability of the insects in the newly invaded stands and the generally strongly negative perception of the problem by the local community, make the Integrated Pest management necessary. Profitability of IPM is shown when possible loss of the public functions of forests such as soil protection, carbon fixation and the risk of damage to public health, are taken into account.