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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
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Resumo(s)
Thaumetopoea pityocampa is the most important pine defoliator in the Mediterranean
24 basin. Despite being attacked by a number of natural enemies, populations occur
25 frequently at high density in several areas.
26 2 Egg parasitism was studied in 27 pine and cedar forests in Algeria, in relation to the host
27 density (tents per tree) and the proportion of forest cover in the landscape.
28 3 Egg parasitism varied from 2 to 25%, accounted by two parasitoid species the specialist
29 Baryscapus servadeii and the generalist Ooencyrtus pityocampae.
30 4 Tent density was negatively correlated with parasitism by B. servadeii but not with that of
31 O. pityocampae. Conversely, parasitism by O. pityocampae increased with the proportion
32 of forest and agricultural cover, but not that of B. servadeii.
33 5 Maximum summer temperature showed no correlation with parasitism rates. Still,
34 temperature frequently exceeded 40ºC during the period of adult parasitoid activity.
35 6 The low performance of the egg parasitoids at the southern edge of the host range could
36 be explained by the reduced fecundity of the host, climate effects, and phenological
37 mismatching between the parasitoids and the egg development. These and other factors
38 potentially involved need to be further explored with a long-term study of population
39 dynamics.
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Palavras-chave
egg parasitism Thaumetopoea pityocampa density-dependent response land-use specialist parasitoid generalist parasitoid climate