Population monitoring of the pine processionary moth (Lepidoptera: Thaumetopoeidae) with pheromone-baited traps

A series of tests were carried out to design pheromone-based monitoring of the pine processionary moth (PPM), Thaumetopoea pityocampa. In a dose–response field test the number of male captures increased significantly with the dosage of pityolure to a plateau around 10 mg. The activity of pheromone dispensers persisted for at least 11 weeks, enough to cover the entire flight period of T. pityocampa. In a comparison of several saturating and non-saturating trap designs, plate sticky traps always showed the highest trapping efficiency. Captures were significantly higher in regularly cleaned traps than in traps without cleaning, and at tree canopy height; however, the latter were positively correlated with captures from traps positioned at breast height. The relationship between the number of PPM males captured in pheromone traps and the density of winter nests was investigated in 14 stands of the maritime pine (Pinus maritima) using 10 traps baited with low doses of pityolure. Mean trap captures calculated from 3 traps schemes to 10 traps were significantly correlated with nest density, indicating that four plate sticky traps baited with 0.2 mg of pityolure would provide a cost-effective tool for monitoring population densities of PPM per hectare. The reliability of this design was tested in 33 pine stands of different age and tree species across a range of geographic regions (France, Italy, Portugal), both in the core and expansion areas of the pest. The results were remarkably consistent, showing significant and positive correlations between mean male captures per day and total number of winter nests per hectare irrespective of the regions. The correlations with the level of infestation in the following generation was also positive for all regions although less significant. Our findings suggest that pheromone-baited traps provide a suitable tool for monitoring of T. pityocampa populations.