Long-term Studies on Egg Parasitoids of Pine Processionary Moth (Thaumetopoea pityocampa) in a New Locality in Bulgaria

Abstract

During the period 1995-2014, the species composition of egg parasitoids of pine processionary moth (Thaumetopoea pityocampa) and their impact on host number was studied in Lisets Mt. near the town of Kyustendil, where the pest was first found in 1993. The study site is located 10 km to the west of stands constantly attacked by pine processionary moth and is isolated from them by deciduous forests, farms and urban areas. For all study period a total of 96 egg batches, containing 21 357 eggs were collected in Scots pine (Pinus sylvestris) plantations. They were separated singly in test tubes covered with cotton stoppers and were reared in laboratory conditions at room temperature (20-22°C). The emergence of egg parasitoids was observed daily. In the end of the studies, all eggs were analysed in detail. Four primary parasitoids (Ooencyrtus pityocampaе, Baryscapus servadeii, Anastatus bifasciatus, Trichogramma embryophagum) and one hyperparasitoid (Baryscapus transversalis) were established in the new locality of the host. In first years, T. embryophagum was the most numerous egg parasitoid of T. pityocampa. Some aspects of its biology and ecology were examined. The impact of main parasitoids of pine processionary moth (B. servadeii and O. pityocampaе) was unstable. In 2014, twenty-one years after the appearance of T. pityocampa in studied habitat, the regulating effect of egg parasitoids is comparable to that in old habitats.