Regional impacts of periodical cicadas on oak radial increment

We investigated the effects of periodical cicadas (Magicicada spp.) on growth of their hosts using records of radial tree-ring growth on oaks (Quercus spp., a common host genus) and pines (Pinus spp., a common nonhost genus) growing within the ranges of 13- and 17-year broods. Growth of oaks was significantly depressed during years of adult emergence by about 4%. Effects in years following emergences or in years prior to emergences were variable or absent. Spectral analyses revealed a significant tendency for periodicity in the growth of oaks, but not pines, matching that of the life cycle of the broods. These results provide some of the first evidence for landscape-level effects of a root-feeding insect and demonstrate that periodical cicadas have a small but detectable effect on growth of their hosts on a geographical scale, considerably larger than previously suspected.