Impact of Egg Parasitoids on Pine Processionary Moth Thaumetopoea pityocampa (Denis & Schiffermuller, 1775) (Lepidoptera: Notodontidae) in a New Habitat

In 2010, the pine processionary moth Thaumetopoea pityocampa first appeared in the land of Vetren village situated on the territory of Osogovo Mt. in South-Western Bulgaria. Studies on egg parasitoids were carried out in the new habitat of T. pityocampa. Egg batches from 2013, 2014 and 2016 host's generations were collected in Pinus sylvestris stands. They were transported to the Laboratory of Entomology of Forest Research Institute in Sofia. The egg-batches were put singly in test tubes covered with cotton stoppers and kept at room temperature (20-22 degrees C). Four primary parasitoids (Ooencyrtus pityocampa., Baryscapus servadeii, Anastatus bifasciatus and Trichogramma sp.) and the hyperparasitoid Baryscapus transversalis were identified. The most numerous species was O. pityocampa. but its relative proportion gradually decreased in studied years from 87.9% (2013) to 70.0% (2014) and 23.5% (2016). In the individual batches, a wide range of combinations of parasitoid species was observed. All emerged specimens of O. pityocampa. and B. servadeii were female. In A. bifasciatus population, the emerged specimens were male, and in B. transversalis - of both sexes, at a ratio of 2:1 of female to male individuals. In laboratory conditions, the longest emergence period was established in O. pityocampa. (115-178 days), which ended in July-August. A significant impact (17.3-23.0%) of the parasitoids on T. pityocampa numbers was determined.

Automated summary

The pine processionary moth Thaumetopoea pityocampa was first discovered in a village in South-Western Bulgaria in 2010. Studies on egg parasitoids revealed a significant impact on the moth population, with the main parasitoid gradually decreasing over the years and a variety of different parasitoid combinations observed in different egg batches.