Impacts of periodical cicadas on forest communities through host selection and growth responses

Periodical cicadas (Magicicada spp.) are one of the largest insect emergences in the world and have potential effects on forest communities because of their great densities and broad host ranges. We measured oviposition and emergence of two broods of cicadas (Brood XXIII–2002 emergence, Brood X–2004 emergence) at 52 sites across a range of habitats in southern Indiana. Our data included over 4700 trees from 61 species and represents the largest dataset ever collected on the habitat and host preferences of periodical cicadas. Cicadas significantly preferred certain tree species and avoided others, and these preferences were consistent between the two broods, but differed between mature and early successional forests. The most preferred species for oviposition were dogwood, black locust, red maple, white oak, box elder, ironwood and American elm. In contrast, sumac, red cedar, pawpaw, pin oak, persimmon, and tulip poplar were strongly avoided. Cicadas emerged at higher densities in mature forests but oviposited more in early successional forests, indicating that populations are a shifting mosaic across the successional landscape. To examine the effects of cicada oviposition on tree growth, we experimentally manipulated oviposition rates by netting plots in early successional forests to reduce oviposition, and have measured trunk circumferences for three years. The netting treatment reduced oviposition by 62%. We also harvested saplings with measured levels of oviposition and measured the growth rings for the years before and after the cicada emergence. We will present results on tree growth rate as a function of the degree of damage from cicadas.