Outbreaks of the koa looper moth (Geometridae: Scotorythra paludicola) in Hawaii: History, monitoring, and research

The koa looper (Geometridae: Scotorythra paludicola) is endemic to the Hawaiian Islands. Its caterpillars specialize on the endemic hardwood tree koa, which is very important economically, ecologically, and culturally. The moth experiences occasional, relatively rare, outbreaks, causing defoliation of vast acreage of koa forests on the islands of Maui and Hawaii. It is unknown what triggers these outbreaks, but they tend to start in a localized region and spread outward in waves. A recent outbreak was detected in January 2013 on the East side of Hawaii Island, and it has since spread to virtually all the major koa forests on the island, causing defoliation of more than 50,000 acres of koa as of May 2013. This is the most extensive outbreak of this species ever recorded, and the last time an outbreak was recorded on Hawaii Island was in 1953, making this a rare opportunity to study spread of the outbreak and the developmental, reproductive, and dispersal biology of the moth. Here we give a general overview of the outbreak dynamics and historical accounts, and present preliminary data on density dependent color polymorphism in this species, as well as discuss pheromones as an option for monitoring and control.