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Response of the egg parasitoids of the pine processionary moth to host density and forest cover at the southern edge of the range
Authors:Khaled Bouzar-Essaidi  Manuela Branco  Andrea Battisti  André Garcia  Maria Rosário Fernandes  Younes Chabane  Mourad Bouzemarene  Leïla Benfekih
Institution:1. Laboratory for Research on Plant Production Biotechnology (LBPV), Faculty of Nature and Life Sciences, University of Blida 1, BP 270, Soumaa Road, Blida, 9000 Algeria;2. Forest Research Centre (CEF), School of Agriculture, University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon, Portugal;3. Department DAFNAE, Agripolis Legnaro Padua, University of Padua, Padua, Italy;4. Department of Agronomic Sciences, Faculty of Natural and Life Sciences, University of Khemis Miliana, Theniet El Had Road, 44225 Khemis Miliana, Algeria;5. Laboratory for Research on Medicinal and Aromatic Plants (LRPMA), Faculty of Nature and Life Sciences, University of Blida 1, BP 270, Soumaa Road, Blida, 9000 Algeria
Abstract:
  1. Thaumetopoea pityocampa is the most important pine defoliator in the Mediterranean basin. Despite being attacked by a number of natural enemies, populations occur frequently at high density in several areas.
  2. Egg parasitism was studied in 27 pine and cedar forests in Algeria, in relation to the host density (tents per tree) and the proportion of forest cover in the landscape.
  3. Egg parasitism varied from 2% to 25%, accounted by two parasitoid species, the specialist Baryscapus servadeii and the generalist Ooencyrtus pityocampae.
  4. Tent density was negatively correlated with parasitism by B. servadeii but not with that of O. pityocampae. Conversely, parasitism by O. pityocampae increased with the proportion of forest and agricultural cover, but not in the case of B. servadeii.
  5. Maximum summer temperature showed no correlation with parasitism rates. Still, temperature frequently exceeded 40 °C during the period of adult parasitoid activity.
  6. The low performance of the egg parasitoids at the southern edge of the host range could be explained by the reduced fecundity of the host, climate effects, and phenological mismatching between the parasitoids and the egg development. These and other factors potentially involved the need to be further explored with a long-term study of population dynamics.
Keywords:climate  density-dependent response  egg parasitism  generalist parasitoid  land-use  specialist parasitoid  Thaumetopoea pityocampa
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