Host utilisation by moth and larval survival of pine processionary caterpillar Thaumetopoea pityocampa in relation to food quality in three Pinus species

Abstract 1. The work reported here analysed host utilisation by the pine processionary moth Thaumetopoea pityocampa (Lepidoptera: Thaumetopoeidae), the relationship between moth oviposition patterns and larval performance, the chemical characteristics of the plant in relation to the performance of different larval instars, and the role of these factors in the outbreak capacity of the species. In order to do this, a combination of field and laboratory techniques was used to study three pine species differing in nutritional characteristics.
2. Moths oviposited in the three pine species analysed, although cluster pine received a lower number of batches. Late-instar larvae were able to feed on all three pine species, however first-instar larvae developed on Scots and black pine but died on cluster pine. Consequently, oviposition in cluster pine can be considered an oviposition mistake, and indicates that moths are rather unselective when ovipositing on different pine species.
3. Chemical analysis of needles suggested that the quantity of nitrogen was the main factor responsible for the difference in survival of larvae.
4. The oviposition pattern of the moth and the larval susceptibility to food quality in Thaumetopoea pityocampa agree with the theory that unselective oviposition of the moth is a precondition for eruptive dynamics in phytophagous insects.
5. The success of the larvae depends mainly on the probability of the moth finding a suitable host. This probability is determined strongly by the changes of structure and coverage in Mediterranean pine woodlands, due to human management.