Egg Batches Parasitism of Processionary Moth Thaumetopoea pityocampa (Lepidoptera, Thaumetopoeidae) from Two Atlas Cedar Ecotypes in Algeria

In the Atlas cedar forests located on the northern massifs of the Blidean Atlas and at the eastern extension of the Saharan Atlas, 79 egg batches of processionary moth Thaumetopoea pityocampa (Denis & Schiffermuller, 1775) were collected during the summer period from two sites: Chrea National park (46), and Ouled Yagoub forest (33). To assess the effect of the egg batches characteristics on the parasitism, the eggs were monitored after the hatching of the larvae and/or the emergence of the parasitoids. The average number of eggs/batches in the Ouled Yagoub site (184 eggs) was significantly higher than of the population of Chrea (151). Data analysis showed that the means comparisons of the hatched and unhatched number of eggs between the two sites were significant. In the case of the population of Chrea, the egg mass was laid in the form of a cylinder on twigs of relatively small diameters while for the population of Ouled Yagoub eggs were laid in the form of plates on twigs of larger diameter, thus more exposed to parasitoids. For the two populations, three active egg parasitoids were identified: Ooencyrtus pityocampae (Mercet, 1921) (Encyrtidae), Baryscapus servadeii (Domenichini,1965) (Eulophidae), and Trichogramma embryophagum (Hartig, 1838) (Trichogrammatidae), the most dominant. These parasitoids were heterogeneously distributed on the egg batches collected in the cedar’s plantation of the Chrea, but homogeneously on the egg batches collected in the Ouled Yagoub cedar forest. The activity and distribution of parasitoids on the egg-laying surface are influenced by the form on the branch chosen by the female.

Egg parasitoid complex of the pine processionary moth (Thaumetopoea pityocampa) on the Thasos Island, Greece

The egg parasitoid complex of the pine processionary moth (Thaumetopoea pityocampa) was surveyed for the first time on the Thasos Island, Greece. A total of 96 egg batches containing 20391 eggs were collected between 06 and 10 of September, 2017 from Aleppo pines (Pinus halepensis) at four sites (Skidia, Thimonia, Alyki and Panagia). Four primary parasitoids were identified (Ooencyrtus pityocampae, Baryscapus servadeii, Anastatus bifasciatus and Trichogramma sp.), as well as the hyperparasitoid B. transversalis. Among the parasitoids groups, O. pityocampae was the most common, followed by B. servadeii, whilst the number of other species was low. The highest survival rate was reported for three species: O. pityocampae, B. servadeii and A. bifasciatus, while the highest was the mortality in Trichogramma sp. All emerged adults of O. pityocampae and B. servadeii were female specimens and in A. bifasciatus – males. The number of females of B. transversalis was three times higher than the one of males. Ooencyrtus pityocampae and B. servadeii were the most important parasitoids of T. pityocampa, destroying respectively 27.1% and 9.9% of the host eggs.

Comparative studies of egg parasitoids of the pine processionary moth (Thaumetopoea pityocampa, Den. & Schiff.) in historic and expansion areas in France and Bulgaria

To investigate enemy pressure across the range of the pine processionary moth (Thaumetopoea pityocampa, Den. & Schiff.) as it spreads northwards in Europe because of climate change, a survey of 206 egg batches from historical and newly colonized areas at both the westernmost and the easternmost ends of the front was carried out in 2016–2018. Out of them, 97 egg batches were collected from nine locations in three regions in France and 109 from four localities in two regions in Bulgaria, both within historical and newly colonized ranges of the pest. The average number of eggs per batch collected in Bulgaria (226.6 ± 43.2) was higher than that in France (194.3 ± 50.1). However, the hatching percentage was higher in French samples, varying from 69.8 to 95.7, vs 49.8 to 85.2 per cent in Bulgarian samples. Four primary parasitoids (Ooencyrtus pityocampae, Baryscapus servadeii, Anastatus bifasciatus, Trichogramma sp.) and a hyperparasitoid (Baryscapus transversalis, found only in two regions of the historical range in Bulgaria) were identified. The oligophagous species B. servadeii was present at all sites within the historical range of the pest. In newly colonized areas, the impact of primary parasitoids on the host was distinctly low, suggesting that they lag behind the range expansion of pine processionary moth. In France, the most abundant species in the T. pityocampa parasitoid complex were B. servadeii in Ré Island and Orléans (97.3 and 87.4 per cent, respectively), and Trichogramma sp. (99.7 per cent) in a newly colonized locality in Fréhel. Ooencyrtus pityocampae prevailed in three of four Bulgarian localities (72.1 per cent in Sandanski, 89.7 per cent in Maglizh and 65.7 per cent in Sladak kladenets), whereas B. servadeii was the most abundant in Gega (75.4 per cent). Mortality of B. servadeii and O. pityocampae caused by the hyperparasitoid B. transversalis amounted to 4.8–6.2 per cent. The impact of predators on the pine processionary moth in the egg stage was negligible at most sites, reaching 12.5 per cent in only one site (Maglizh).