Insect damage to cones of exotic conifer species introduced in arboreta I. Interspecific variations within the genus Picea.
The cone entomofauna of native Norway spruce [Picea abies] was compared with that of 28 exotic species introduced in 2 French arboreta. Thirty-two insect species (including 11 species of parasitoids, 3 predators, 13 phytophagous and detritivorous insects and 1 hibernating species) were observed. Most were native to P. abies. The seed wasp Megastigmus atedius was the only phytophagous pest introduced with its hosts from North America and is recorded for the 1st time in France. The number of insect species that colonized cones was directly related to the phylogenetic and geographic proximity of the exotic spruce to P. abies and to its flowering phenology. Early-flowering Picea species of the abies group, originating from the Himalayas and central China, were attacked by insects the most, followed by Euro-Caucasian species of the omorika group. The host range observed in each phytophage showed that damage was more related to Picea phylogeny, as insects were specialized in cone exploitation. The importance of entomological studies in arboreta was clearly demonstrated, as evidenced by the potential for native insects to shift to exotic species and by the detection of introduced seed chalcids.