Defoliation of the Invasive Tree Falcataria moluccana on Hawaii Island by the Native Koa Looper Moth (Geometridae: Scotorythra paludicola), and Evaluation of Five Fabaceous Trees as Larval Hostplants

Abstract

The koa looper (Geometridae: Scotorythra paludicola) is an endemic Hawaiian moth whose caterpillars feed on Acacia koa, and experience occasional outbreaks, producing vast defoliations of forests. During an extensive and ongoing outbreak of this species on the island of Hawaii, patchy defoliation of Falcataria moluccana (“albizia”) was observed in the vicinity of Akaka Falls State Park, relatively distant from the main defoliation of koa, raising questions about the host range of the koa looper. To identify suitable host plants in the laboratory, we of- fered the koa looper foliage from five fabaceous tree species (A. koa, A. confusa, F. moluccana, Prosopis pallida, and Leucaena leucocephala), and recorded feeding and performance on these diets. Among the five tree species, only A. koa and F. moluccana were accepted as food; caterpillars on the other three species all died by the fifth day of the trial. Survival of the koa looper to pupation and adulthood on F. moluccana did not differ significantly from that on A. koa phyllodes, indicating that this tree is a suitable host, though it does not appear to be widely utilized in the field. Both oviposition preference and larval requirements are likely important determinants of the realized diet breadth for the koa looper. Additionally, develop- ment times at 19°C on A. koa and F. moluccana were nearly twice as long as at 23°C, highlighting the importance of temperature for development of this insect