This data release includes metadata and tabular data that document the response of koa (Acacia koa) trees to defoliation by the koa moth (Scotorythra paludicola) during 2013-2014 at Hakalau Forest National Wildlife Refuge. Data were collected on 55 plots at 4 sites representing 2 habitat types with either high or low koa densities. Ohia (Metrosideros polymorpha) trees dominated habitats with low koa density. Data sets document (1) locations and habitat type of forest plots where koa trees were evaluated, (2) density and size of koa trees within plots, extent of koa tree defoliation, rate of koa tree foliage regrowth (refoliation), and koa tree mortality, and (3) counts and relative size of ohia trees for evaluating forest structure within plots.